1. Research www. AJOG.org
OBSTETRICS
Identification of patients at risk for early onset and/or severe
preeclampsia with the use of uterine artery Doppler
velocimetry and placental growth factor
Jimmy Espinoza, MD; Roberto Romero, MD; Jyh Kae Nien, MD; Ricardo Gomez, MD; Juan Pedro Kusanovic, MD;
Luis F. Gonçalves, MD; Luis Medina, MD; Sam Edwin, PhD; Sonia Hassan, MD; Mario Carstens, MD; Rogelio Gonzalez, MD
OBJECTIVE: Preeclampsia has been proposed to be an antiangio- RESULTS: (1) The prevalence of preeclampsia, severe preeclampsia,
genic state that may be detected by the determination of the con- and early onset preeclampsia were 3.4% (113/3296), 1.0% (33/3296),
centrations of the soluble vascular endothelial growth factor recep- and 0.8% (25/3208), respectively. UADV was performed in 95.4%
tor-1 (sVEGFR-1) and placental growth factor (PlGF) in maternal (3146/3296) and maternal plasma PlGF concentrations were deter-
blood even before the clinical development of the disease. The pur- mined in 93.5% (3081/3296) of the study population. (2) Abnormal
pose of this study was to determine the role of the combined use of UADV and a maternal plasma PlGF of 280 pg/mL were independent
uterine artery Doppler velocimetry (UADV) and maternal plasma risk factors for the occurrence of preeclampsia, severe preeclampsia,
PlGF and sVEGFR-1 concentrations in the second trimester for the early onset preeclampsia, and SGA without preeclampsia. (3) Among
identification of patients at risk for severe and/or early onset patients with abnormal UADV, maternal plasma PlGF concentration
preeclampsia. contributed significantly in the identification of patients destined to de-
velop early onset preeclampsia (area under the curve, 0.80; P .001)
STUDY DESIGN: A prospective cohort study was designed to examine and severe preeclampsia (area under the curve, 0.77; P .001). (4) In
the relationship between abnormal UADV and plasma concentrations contrast, maternal plasma sVEGFR-1 concentration was of limited use
of PlGF and sVEGFR-1 in 3348 pregnant women. Plasma samples in the prediction of early onset and/or severe preeclampsia. (5) The
were obtained between 22 and 26 weeks of gestation at the time of combination of abnormal UADV and maternal plasma PlGF of 280
ultrasound examination. Abnormal UADV was defined as the presence pg/mL was associated with an odds ratio (OR) of 43.8 (95% CI, 18.48-
of bilateral uterine artery notches and/or a mean pulsatility index above 103.89) for the development of early onset preeclampsia, an OR of 37.4
the 95th percentile for the gestational age. Maternal plasma PlGF and (95% CI, 17.64-79.07) for the development of severe preeclampsia, an OR
sVEGFR-1 concentrations were determined with the use of sensitive of 8.6 (95% CI, 5.35-13.74) for the development of preeclampsia, and an
and specific immunoassays. The primary outcome was the develop- OR of 2.7 (95% CI, 1.73-4.26) for the delivery of a SGA neonate in the
ment of early onset preeclampsia ( 34 weeks of gestation) and/or absence of preeclampsia.
severe preeclampsia. Secondary outcomes included preeclampsia, the CONCLUSION: The combination of abnormal UADV and maternal
delivery of a small for gestational age (SGA) neonate without pre- plasma PlGF concentration of 280 pg/mL in the second trimester is
eclampsia, spontaneous preterm birth at 32 and 35 weeks of ges- associated with a high risk for preeclampsia and early onset and/or
tation, and a composite of severe neonatal morbidity. Contingency ta- severe preeclampsia in a low-risk population. Among those with ab-
bles, chi-square test, receiver operating characteristic curve, and normal UADV, a maternal plasma concentration of PlGF of 280
multivariate logistic regression were used for statistical analyses. A pg/mL identifies most patients who will experience early onset and/or
probability value of .05 was considered significant. severe preeclampsia.
From the Perinatology Research Branch, NICHD/NIH/DHHS, Bethesda, MD, and Detroit, MI (Drs Espinoza, Romero, Nien, Kusanovic,
Gonçalves, Edwin, and Hassan); the Department of Obstetrics and Gynecology, Wayne State University/Hutzel Hospital (Drs Espinoza,
Gonçalves, and Hassan), and the Center for Molecular Medicine and Genetics, Wayne State University (Dr Romero), Detroit, MI; and
CEDIP, Department of Obstetrics and Gynecology, Sotero del Rio Hospital, Puente Alto, Chile (Drs Gomez, Medina, Carstens, and
Gonzalez).
Reprints not available from the authors. Address correspondence to Roberto Romero, MD, Perinatology Research Branch, NICHD/NIH/DHHS,
Wayne State University/Hutzel Women’s Hospital, 3990 John R, Box 4, Detroit, MI 48201; warfiela@mail.nih.gov
Supported by the Intramural Research Program of the National Institute of Child Health and Human Development, NIH, DHHS.
0002-9378/$32.00
© 2007 Mosby, Inc. All rights reserved.
doi: 10.1016/j.ajog.2006.11.002
326.e1 American Journal of Obstetrics & Gynecology APRIL 2007

2. www.AJOG.org Obstetrics Research
Key words: gestational hypertension, placental growth factor (PlGF), growth factor receptor-1 (VEGFR-1), uterine artery Doppler
preeclampsia, small for gestational age, soluble vascular endothelial velocimetry, vascular endothelial growth factor (VEGF)
Cite this article as: Espinoza J, Romero R, Nien JK, et al. Identification of patients at risk for early onset and/or severe preeclampsia with the use of uterine
artery Doppler velocimetry and placental growth factor. Am J Obstet Gynecol 2007;196:326.e1-326.e13.
P reeclampsia is a leading cause of preg-
nancy-related maternal death.1-3 The
earlier the gestational age at diagnosis, the
M ATERIAL AND M ETHODS
Study design
A prospective cohort study was con-
Human Investigation Committee of the
Sotero del Rio Hospital, Santiago, Chile
(an affiliate of the Pontificia Catholic
higher the risk of maternal death exists.1 ducted between January 1998 and April University of Santiago), and the Institu-
For example, the risk of maternal death is 4 2004 to examine the relationship be- tional Review Board of the National In-
times higher if preeclampsia develops be- tween UADV and plasma concentra- stitute of Child Health and Human De-
tween 32 weeks of gestation than after this tions of PlGF and sVEGFR-1 in pregnant velopment of the National Institutes of
gestational age. Thus, the identification of women. Plasma samples were obtained Health.
patients at risk for severe and/or early onset at the time of ultrasound examination
preeclampsia followed by prophylactic in- between 22 and 26 weeks of gestation. UADV
terventions may prevent or delay the clin- Preeclampsia was diagnosed in the pres- Five experienced sonographers per-
ical presentation of the disease and/or re- ence of gestational hypertension (sys- formed Doppler ultrasound of the uter-
duce its severity. tolic blood pressure 140 mm Hg or di- ine arteries at the time of blood sampling
Abnormal uterine artery Doppler ve- astolic blood pressure 90 mm Hg on at using real-time ultrasound equipment
locimetry (UADV)4-8 as well as abnormal least 2 occasions, 6 hours to 1 week (ACUSON 128-XP; Acuson Corporation,
maternal plasma concentration of proan- apart) and proteinuria ( 300 mg in a Mountain View, CA) with a 3.5-MHz or a
giogenic and antiangiogenic factors are 24-hour urine collection or 1 dipstick 5-MHz curvilinear probe. The right and
risk factors for the subsequent develop- measurement of 2 ). Patients with left uterine arteries were identified in an
ment of preeclampsia.9-14 Recently, it has preeclampsia were subclassified as either oblique plane of the pelvis at the crossover
been reported that UADV between 22 and early-onset ( 34 weeks of gestation) or with the external iliac arteries, and the
25 weeks of gestation is the “best test” for late-onset ( 34 weeks of gestation) dis- Doppler signals were sampled. When 3
the identification of patients destined to ease according to the gestational age at similar consecutive waveforms were ob-
develop preeclampsia, compared with bio- which preeclampsia was diagnosed. Se- tained, the pulsatility index of the right and
chemical indicators in the maternal vere preeclampsia was defined as severe left uterine arteries were measured, and the
plasma, such as markers for (1) lipid per- gestational hypertension (diastolic mean pulsatility index of the 2 vessels was
oxidation (F2-isoprostane), (2) total anti- blood pressure 110 mm Hg) and mild calculated. The presence of an early dia-
oxidant capacity of plasma (ferric reducing proteinuria or mild gestational hyper- stolic notch in the uterine arteries was de-
ability of plasma and uric acid concentra- tension and severe proteinuria (a 24- termined according to the criteria pro-
tions), (3) antioxidant enzymes in erythro- hour urine sample that contained 3.5 g posed by Bower et al.17 An abnormal
cytes (catalase, superoxide dismutase, and protein or a urine specimen of 3 pro- UADV was defined as the presence of bi-
glutathione peroxidase), (4) putative tein by dipstick measurement). Patients lateral uterine artery notches and/or a
markers for endothelial cell dysfunction with an abnormal liver function test (as- mean pulsatility index of 95th percentile
(von Willebrand factor, plasminogen ac- partate aminotransferase 70 IU/L) and for the gestational age.
tivator inhibitor types 1 and 2, and thrombocytopenia (platelet count
thrombomodulin), and (5) pro- and an- 100,000/cm3) were also classified as Sample collection and human
tiangiogenic factors (placental growth having severe preeclampsia. Small for sVEGFR-1 immunoassay
factor [PlGF], vascular endothelial gestational age (SGA) neonate was de- Venipuncture was performed, and the
growth factor [VEGF], and soluble vas- fined as a birthweight of 10th percen- blood was collected into tubes that con-
cular endothelial growth factor recep- tile for the gestational age at birth, ac- tained EDTA. The samples were centri-
tor-1 [sVEGFR-1]).15 The purpose of cording to the national birthweight fuged for 10 minutes at 4°C and stored at
this study was to determine whether the distribution of a Hispanic population.16 70°C until assayed. The concentra-
maternal plasma concentration of the Patients with chronic hypertension, tions of sVEGFR-1 were measured with
angiogenic factor PlGF and the antian- multiple pregnancies, fetal anomalies, or an enzyme-linked immunosorbent assay
giogenic factor sVEGFR-1 in the mid tri- chronic renal disease were excluded (R&D Systems, Minneapolis, MN). The
mester of pregnancy can improve the from the study. All women provided details of the method have been de-
risk assessment determined by UADV written informed consent before the col- scribed previously.18 The inter- and in-
for severe and/or early onset lection of plasma samples. The collection traassay coefficients of variation for hu-
preeclampsia. and use of samples was approved by the man sVEGFR-1 immunoassay in our
APRIL 2007 American Journal of Obstetrics & Gynecology 326.e2

3. Research Obstetrics www.AJOG.org
laboratory were 4.8% and 6.9%, respec- radiologic confirmation. Additional (33/3296), and 0.8% (25/3208), respec-
tively. The sensitivity of the assay was secondary outcomes included abruptio tively. UADV was performed in 95.4%
17.8 pg/mL. The maternal plasma con- placentae and eclampsia. We have also in- (3146/3296), and plasma PlGF concen-
centrations of sVEGFR-1 were deter- cluded nonobjective definitions of early trations were determined in 93.5%
mined only among patients with abnor- onset preeclampsia (such as “preeclampsia (3081/3296) of the study population.
mal UADV. requiring delivery at 34 weeks”19,20) to Early onset preeclampsia developed in 5
provide the basis for comparison with pre- patients, severe preeclampsia developed
Human PlGF assays vious reports. in 13 patients, and both early onset and
A specific and sensitive enzyme-linked severe preeclampsia developed in 20 pa-
immunosorbent assay was used to deter- tients (this group does not include the
Statistical analysis
mine concentrations of PlGF in maternal former 18 patients).
Comparisons between proportions were
plasma (R&D Systems). Briefly, human
performed with chi-square or Fisher’s
plasma samples were incubated in dupli-
exact test. Receiver operating character-
Diagnostic indices, predictive
cate wells of the microtiter plates, which
istic curves were constructed to describe
values, and likelihood ratios
had been coated with monoclonal anti-
the relationship between sensitivity and
of UADV
bodies to human PlGF. During this incu- An abnormal UADV was present in
the false-positive rate (1-specificity) of
bation, plasma PlGF (antigen) binds to 11.3% (354/3146) of the study popula-
plasma PlGF and sVEGFR-1 in the iden-
monoclonal antibodies of PlGF to form tion. The diagnostic indices, predictive
tification of patients destined to develop
antigen-antibody complexes. After values, and likelihood ratios for the pri-
early onset and/or severe preeclampsia.
unbound substances were washed mary outcomes are displayed in Table 1.
Survival analysis was used to compare
away, horseradish peroxidase– conju- Logistic regression analysis indicated
the examination-to-diagnosis interval in
gated polyclonal antibodies specific for that an abnormal UADV, between 22
patients who had preeclampsia, accord-
PlGF were added to each well of the mi- and 26 weeks of gestation, was an inde-
ing to the results of the UADV and ma-
crotiter plate. After the second incuba- pendent explanatory variable for the oc-
ternal plasma PlGF concentration. Lo-
tion, the unbound antibody-enzyme re- currence of preeclampsia, early onset
gistic regression analysis was used to
agent was removed by repeated washing, preeclampsia, severe preeclampsia, and
explore the relationship between the oc-
and a substrate solution was added. SGA without preeclampsia, after an ad-
currence of the outcomes and the follow-
Color developed in proportion to the justment was made for maternal age of
ing explanatory variables: maternal
amount of PlGF in each well. The inten- 35 years, previous preeclampsia, nulli-
plasma PlGF concentration, maternal
sity of the color was measured by a pro- parity, smoking, first trimester body
age of 35 years, previous preeclampsia,
grammable spectrophotometer (Ceres mass index of 30 kg/m2, maternal
nulliparity, first trimester body mass in-
900 Micro plate Workstation; Bio-Tek plasma PlGF, and sample storage time
dex of 30 kg/m2, smoking status, and
Instruments, Winooski, VT). Concen- (Table 2).
sample storage time. A power analysis
trations of the samples were derived by
indicated that this study had adequate
interpolation of the absorbance readings
power ( 90%) to determine the role of
Diagnostic indices, predictive
from a standard curve that was generated
the combination of abnormal UADV
values, and likelihood ratios
with known concentrations of PlGF.
and maternal plasma PlGF concentra-
of maternal plasma PlGF
Calculated inter- and intraassay coeffi-
tion in the prediction of the outcomes,
concentration
cients of variation for PlGF immunoas- Receiver operating characteristic curve
except for spontaneous preterm delivery
says in our laboratory were 4.60% and analysis was performed to examine the
at 32 weeks of gestation. The statistical
2.27%, respectively. The detection limit diagnostic performance of maternal
packages used were SPSS software (ver-
(sensitivity) of the assay was 10.7 pg/mL. plasma PlGF concentrations in the iden-
sion 12.0; SPSS Inc, Chicago, IL), Med-
tification of the patient destined to de-
Calc software (version 7.4.4.1; MedCalc
Study outcomes Software, Mariakerke, Belgium), and
velop early onset and/or severe pre-
The primary outcome was the diagnosis eclampsia; a cut-off of 280 pg/mL was
PASS software (NCSS, Kaysville, UT). A
of early onset preeclampsia and/or se- selected. Logistic regression analysis in-
probability value of 0.05 was consid-
vere preeclampsia. Secondary outcomes dicated that a maternal plasma concen-
ered significant.
included preeclampsia, SGA without tration of PlGF 280 pg/mL was an in-
preeclampsia, spontaneous preterm de- dependent explanatory variable for the
livery at 35 and 32 weeks of gestation, R ESULTS occurrence of preeclampsia, early onset
examination-to-diagnosis interval among Prevalence of the outcomes preeclampsia, severe preeclampsia, and
patients who had preeclampsia, and a This study included 3348 patients (52 SGA without preeclampsia after an ad-
composite of severe neonatal morbidity patients were lost to follow-up evalua- justment was made for the aforemen-
that included intraventricular hemor- tion). The prevalence of preeclampsia, tioned covariates and abnormal UADV.
rhage, necrotizing enterocolitis, and hya- severe preeclampsia, and early onset pre- The odds ratio and 95% CI of a low ma-
line membrane disease with sonographic/ eclampsia was 3.4% (113/3296), 1.0% ternal plasma PlGF concentration
326.e3 American Journal of Obstetrics & Gynecology APRIL 2007

4. www.AJOG.org Obstetrics Research
TABLE 1
Diagnostic indices of abnormal UADV in the identification of patients destined to develop preeclampsia,
early onset preeclampsia, and/or severe preeclampsia and patients whose
condition required delivery at <34 weeks of gestation
Positive Negative Likelihood Likelihood
predictive value predictive value ratio[ ] ratio[ ]
Outcome Sensitivity (%)* Specificity (%)* (%)* (%)* (95% CI) (95% CI)
Preeclampsia 35.5 (39/110) 89.6 (2721/3036) 11 (39/354) 97.5 (2721/2792) 3.42 (2.60-4.49) 0.72 (0.55-0.95)
................................................................................................................................................................................................................................................................................................................................................................................
Early onset 72 (18/25) 89.6 (2721/3036) 5.4 (18/333) 99.7 (2721/2728) 6.94 (5.32-9.05) 0.31 (0.24-0.41)
preeclampsia ( 34
weeks of gestation)
................................................................................................................................................................................................................................................................................................................................................................................
Severe preeclampsia 72.7 (24/33) 89.4 (2783/3113) 6.8 (24/354) 99.7 (2783/2792) 6.86 (5.44-8.66) 0.31 (0.24-0.38)
................................................................................................................................................................................................................................................................................................................................................................................
Preeclampsia that required 86.7 (13/15) 89.5 (2726/3046) 3.9 (13/333) 99.9 (2726/2728) 8.25 (6.59-10.32) 0.15 (0.12-0.19)
delivery at 34 weeks
of gestation
................................................................................................................................................................................................................................................................................................................................................................................
* Data in parentheses represents proportions.
( 280 pg/mL) in the identification of dependent explanatory variable for the the identification of patients destined
the outcomes are given in Table 2, and outcomes after being controlled for the to have early onset preeclampsia (area
the diagnostic indices of a low maternal aforementioned covariates. This param- under the curve, 0.80; P .001) and
plasma concentration of PlGF for the eter combination was associated with an severe preeclampsia (area under the
primary outcomes are given in Table 3. odds ratio of 43.8 (95% CI, 18.48-103.9) curve, 0.77; P .001; Figure 1A and B).
and 37.4 (95% CI, 17.6-79.1) to develop Indeed, 89% of the women (16/18)
The combination of abnormal early onset preeclampsia and severe pre- with abnormal UADV results who had
UADV and maternal plasma PlGF eclampsia, respectively. Thus, abnormal early onset preeclampsia and 84% of
<280 pg/mL in the identification UADV and low maternal plasma con- the women (21/25) who had severe
of the outcomes centration of PlGF conferred a much preeclampsia had a plasma PlGF con-
Table 4 gives the diagnostic indices, pre- higher risk for the development of early centration of 280 pg/mL. In contrast,
dictive values, and likelihood ratios of onset and/or severe preeclampsia than maternal plasma sVEGFR-1 concen-
the combination of abnormal UADV abnormal UADV alone (Tables 2 and 5). tration was of limited value in the pre-
and maternal plasma PlGF of 280 diction of early onset (area under the
pg/mL for the identification of the pri- Maternal plasma PlGF and curve, 0.49; P .9) and severe pre-
mary outcomes. This combined ap- sVEGFR-1 in the identification of eclampsia (area under the curve, 0.54;
proach improved the positive predictive patients destined to have early P .5; Figure 1A and B).
value of an abnormal UADV in the pre- onset and/or severe Among patients with normal UADV,
diction of the primary study outcomes preeclampsia, according to the the maternal plasma PlGF concentration
without a significant reduction in the results of the UADV did not contribute to the identification
sensitivity. Multivariate logistic regres- A subanalysis indicated that, among of patients destined to develop early on-
sion analysis indicated that the combina- patients with an abnormal UADV re- set preeclampsia (area under the curve,
tion of abnormal UADV and maternal sult, the maternal plasma PlGF con- 0.56; P .6) or severe preeclampsia (area
plasma PlGF of 280 pg/mL was an in- centration contributed significantly to under the curve, 0.62; P .2).
TABLE 2
Logistic regression analysis of abnormal UADV or maternal plasma PlGF concentration of <280 pg/mL
for the prediction of the outcomes adjusted for maternal age, previous preeclampsia, nulliparity,
smoking status, body mass index, and sample storage time
Abnormal UADV PlGF concentration of <280 pg/mL
Outcome Odds ratio 95% CI Odds ratio 95% CI
Preeclampsia 4.3 2.82-6.66 2.6 1.67-3.94
................................................................................................................................................................................................................................................................................................................................................................................
Preeclampsia at 34 weeks of gestation 24.1 9.61-60.44 5.5 1.98-15.08
................................................................................................................................................................................................................................................................................................................................................................................
Severe preeclampsia 21.1 9.47-47.14 6.5 2.59-16.34
................................................................................................................................................................................................................................................................................................................................................................................
SGA without preeclampsia 1.7 1.16-2.35 1.6 1.20-2.04
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TABLE 3
Diagnostic indices of a maternal PlGF concentration of <280 pg/mL in the identification of patients destined
to develop preeclampsia, early onset preeclampsia, severe preeclampsia, and patients whose condition
required delivery at <34 weeks of gestation
Positive Negative Likelihood Likelihood
Sensitivity predictive value predictive value ratio[ ] ratio[ ]
Outcome (%)* Specificity (%)* (%)* (%)* (95% CI) (95% CI)
Preeclampsia 69.1 (76/110) 51.4 (1536/2988) 5 (76/1528) 97.8%(1536/1570) 1.42 (1.25-1.62) 0.60 (0.53-0.68)
................................................................................................................................................................................................................................................................................................................................................................................
Early onset 80 (20/25) 51.4 (1527/2971) 1.4 (20/1464) 99.7 (1527/1532) 1.65 (1.35-2.01) 0.39 (0.32-0.48)
preeclampsia ( 34
weeks of gestation)
................................................................................................................................................................................................................................................................................................................................................................................
Severe preeclampsia 81.8 (27/33) 51.0 (1555/3048) 1.8 (27/1520) 99.6 (1555/1561) 1.67 (1.42-1.97) 0.36 (0.30-0.42)
................................................................................................................................................................................................................................................................................................................................................................................
Preeclampsia that required 86.7 (13/15) 51.3 (1530/2981) 0.9% (13/1464) 99.9 (1530/1532) 1.78 (1.46-2.18) 0.26 (0.21-0.32)
delivery at 34 weeks
of gestation
................................................................................................................................................................................................................................................................................................................................................................................
* Data in parentheses represents proportions.
Demographic and clinical eclampsia, placental abruption, eclamp- of UADV followed by maternal plasma
characteristics of the study sia, and a composite of severe neo- PlGF determinations in the second trimes-
population, according to UADV natal morbidity than both patients ter. The prevalence of early onset and/or
and maternal plasma PlGF with normal UADV results and those severe preeclampsia among patients with
concentration with abnormal UADV results and a abnormal UADV and PlGF concentra-
Tables 6 and 7 display the demographic maternal plasma concentration of tions of 280 pg/mL was 11 times higher
and clinical characteristics of the pop- PlGF of 280 pg/mL (chi-square for than among those with abnormal UADV
ulation as well as the outcomes accord- trend; P .001). and PlGF concentrations of 280 pg/mL
ing to the results of the UADV and ma- (15.7% [22/140] vs 1.4% [3/207]; P
ternal plasma PlGF concentration of .001) and 30 times higher than among pa-
280 pg/mL, respectively. There were Sequential screening with UADV tients with normal UADV results, regard-
no differences in gestational ages at ul- and maternal plasma PlGF less of the maternal plasma PlGF concen-
trasound examination among the concentration in the identification tration (15.7% [22/140] vs 0.5%
study groups. Patients with abnormal of patients destined to develop [13/2792]; P .001; Figure 3).
UADV results and maternal plasma early onset and/or severe Figure 4 displays the distribution of
PlGF concentrations of 280 pg/mL preeclampsia the study population as a result of the
had a higher frequency of preeclamp- Figures 2 and 3 display the distribution of sequential determination of maternal
sia, early onset preeclampsia, severe the study population according to the re- plasma concentration of PlGF followed
preeclampsia, SGA without pre- sults of sequential assessment with the use by UADV. This flow diagram was gener-
TABLE 4
Diagnostic indices of a combination of abnormal UADV and maternal plasma PlGF concentration of <280
pg/mL in the identification of patients destined to develop preeclampsia, early onset preeclampsia,
and/or severe preeclampsia and patients whose condition required delivery at <34 weeks of gestation
Positive Negative Likelihood Likelihood
Sensitivity predictive value predictive value ratio[ ] ratio[ ]
Outcome (%)* Specificity (%)* (%)* (%)* (95% CI) (95% CI)
Preeclampsia 27.3 (30/110) 96.4 (2926/3036) 21.4 (30/140) 97.3 (2926/3006) 7.53 (5.27-10.75) 0.75 (0.53-1.08)
................................................................................................................................................................................................................................................................................................................................................................................
Early onset 64 (16/25) 96.5 (3066/3176) 12.7 (16/126) 99.7 (3066/3075) 18.48 (13.07-26.13) 0.37 (0.26-0.53)
preeclampsia ( 34
weeks of gestation)
................................................................................................................................................................................................................................................................................................................................................................................
Severe preeclampsia 63.6 (21/33) 96.3 (3136/3255) 15.0 (21/140) 99.6 (3136/3148) 17.41 (12.74-23.79) 0.38 (0.28-0.52)
................................................................................................................................................................................................................................................................................................................................................................................
Preeclampsia that required 73.3 (11/15) 96.4 (3071/3186) 8.7 (11/126) 99.9 (3071/3075) 20.32 (14.26-28.95) 0.28 (0.19-0.40)
delivery at 34 weeks
of gestation
................................................................................................................................................................................................................................................................................................................................................................................
* Data in parentheses represents proportions.
326.e5 American Journal of Obstetrics & Gynecology APRIL 2007

6. www.AJOG.org Obstetrics Research
low urine concentration of PlGF be-
TABLE 5 tween 25 and 28 weeks has been asso-
Logistic regression analysis of a combination of abnormal UADV and ciated recently with a high risk for
maternal plasma PlGF concentration of <280 pg/mL for the prediction preeclampsia.13
of the outcomes that are adjusted for maternal age, previous The results presented herein differ
preeclampsia, nulliparity, smoking status, body mass index, from those reported recently,22 indicat-
and sample storage time ing a lack of association between abnor-
Abnormal UADV PlGF mal UADV and low PlGF. Differences in
concentration of <280 pg/mL sample size, gestational age at ultra-
Outcome Odds ratio 95% CI sound, and study outcomes may account
Preeclampsia 8.6 5.35-13.74 for these discrepancies. A recent longitu-
..............................................................................................................................................................................................................................................
dinal study that included 81 patients at
Preeclampsia at 34 weeks of gestation 43.8 18.48-103.89
.............................................................................................................................................................................................................................................. risk for preeclampsia reported that the
Severe preeclampsia 37.4 17.64-79.07 maternal plasma PlGF concentration at
..............................................................................................................................................................................................................................................
SGA without preeclampsia 2.7 1.73-4.26 24 weeks of gestation contributed signif-
icantly to the prediction of the disease.23
However, this study did not include
ated because many centers in the United tration of 280 pg/mL, between 22 enough patients to determine the value
States do not use UADV. and 26 weeks of gestation, identifies of maternal plasma PlGF for the predic-
The survival analysis indicated that patients at a very high risk for pre- tion of early onset preeclampsia, and the
patients with abnormal UADV and low eclampsia, early onset preeclampsia, authors cautioned that “large prospec-
PlGF have a shorter examination-to- and severe preeclampsia. tive cohort studies in unselected women
diagnosis interval than those in the These novel observations are consis- are required to ascertain any clinical
other 2 groups (log rank test, 37.9; P tent with previous reports indicating usefulness.”23
.001; Figure 5). that a low maternal plasma concentra- The regulation of vascular growth
tion of PlGF in the first9,12 or second tri- and remodeling, also known as angio-
C OMMENT mester of pregnancy9-11,21 and abnormal genesis, is considered to be central to
The results of this study indicate that a UADV results between 23 and 25 weeks normal placental and fetal growth and
combination of an abnormal UADV of gestation5-8 are risk factors for the de- development.24-26 In the human pla-
and a maternal plasma PlGF concen- velopment of preeclampsia. Similarly, a centa, angiogenesis is biphasic, with
peaks at mid gestation and at term as
FIGURE 1 the result of endothelial proliferation
Receiver operating characteristic curves of the maternal plasma early in pregnancy and vascular re-
concentration of PlGF and sVEGFR-1 for the identification of modeling in the second half of preg-
patients destined to develop early onset or severe preeclampsia nancy.27 This is consistent with the
model of placental angiogenesis pro-
posed by Kingdom et al, 28 whereby
branching angiogenesis is predomi-
nant in the first trimester and is asso-
ciated with high placental production
of VEGF. In contrast, nonbranching
angiogenesis is predominant in the
third trimester and is associated with a
high placental production of PlGF.28
Angiogenesis is regulated by at least 3
growth factor families, which include
VEGFs, angiopoietins, and ephrins.29
Other nonspecific factors that have been
proposed to regulate angiogenesis in-
clude fibroblast growth factors, trans-
Maternal plasma PlGF concentration (solid line) contributed significantly to the prediction of patients forming growth factors and , tumor
destined to develop A, early onset preeclampsia (PE; P .001) and B, severe preeclampsia (P necrosis factor , interleukin-8, hepato-
.001). In contrast, maternal plasma sVEGFR-1 concentration (dotted line) was of limited use in the cyte growth factor, angiogenin, and
prediction of A, early onset preeclampsia (area under the curve [AUC], 0.49; P .9) and B, severe members of the Notch family.26,30,31 Re-
preeclampsia (area under the curve, 0.54; P .5). cent evidence indicates that angiogenesis
requires the sequential activation of sev-
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TABLE 6
Demographic and clinical characteristics of the study population according to UADV and maternal plasma
PlGF concentration
Abnormal UADV Abnormal UADV
PlGF concentration PlGF concentration of
Normal UADV* of >280 pg/mL <280 pg/mL
Variable (n 2792) (n 207) (n 140) P value
†
Maternal age (y) 27 (14-46) 23 (14-43) 24 (16-42) .001
................................................................................................................................................................................................................................................................................................................................................................................
‡
Nulliparity (%) 33.9 (947/2792) 57 (118/207) 54.3 (76/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Preeclampsia in a previous 2 (56/2792) 1.9 (4/207) 3.6 (5/140) NS
pregnancy (%)‡
................................................................................................................................................................................................................................................................................................................................................................................
2†
Body mass index (kg/m ) 24.5 (16.2-89) 23.1 (15.9-37.1) 24.6 (18.0-44.0) .001
................................................................................................................................................................................................................................................................................................................................................................................
‡
Smokers (%) 7.4 (207/2792) 8.7 (18/207) 3.6% (5/140) NS
................................................................................................................................................................................................................................................................................................................................................................................
Gestational age at 24.1 0.64 24.1 0.60 24.1 0.64 NS
ultrasound (wk)§
................................................................................................................................................................................................................................................................................................................................................................................
Maternal plasma PlGF 279.1 (8.9-2572.0) 456.8 (282.3-2040.0) 172.9 (0-279.8) .001
(pg/mL)†
................................................................................................................................................................................................................................................................................................................................................................................
Maternal plasma sVEGFR-1 — 844 (0-2550) 735 (0-9450) NS
(pg/mL)†
................................................................................................................................................................................................................................................................................................................................................................................
Mean uterine artery 0.77 (0.3-1.4) 1.10 (0.6-2.7) 1.36 (0.6-2.8) .001
pulsatility index†
................................................................................................................................................................................................................................................................................................................................................................................
NS, not significant.
* Regardless of the maternal plasma PlGF concentrations.
†
Data are given as median (range).
‡
Data in parentheses represents proportions.
§
Data are given as mean SD.
eral receptors (which include Tie1, Tie2, VEGFs are a family of dimeric pro- vascular permeability.30,31 VEGF exerts
and platelet-derived growth factor re- teins that include VEGF-A, VEGF-B, its biologic effect through VEGFR-2,
ceptor ) by ligands in endothelial and VEGF-C, VEGF-D, and PlGF.31 The whereas the precise function of
mural cells.32 However, VEGF signaling function of VEGF is to promote the sur- VEGFR-1 is still a subject of debate. Most
represents a critical rate-limiting step in vival, migration, and differentiation of investigators believe that VEGFR-1
physiologic angiogenesis.32 endothelial cells as well as to mediate might not be a receptor that transmits a
TABLE 7
Clinical outcomes of the population according to UADV and maternal plasma PlGF concentration
Abnormal UADV PlGF Abnormal UADV PlGF
Normal UADV of >280 pg/mL of <280 pg/mL
Variable (n 2792) (n 207) (n 140) P value
Preeclampsia 2.5 (71/2792) 4.3 (9/207) 21.4 (30/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Early onset preeclampsia ( 34 weeks of gestation) 0.3 (7/2728) 1 (2/200) 12.7 (16/126) .001
................................................................................................................................................................................................................................................................................................................................................................................
Severe preeclampsia 0.3 (9/2792) 1.4 (3/207) 15 (21/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Birthweight 10th percentile* 8.1 (225/2786) 8.7 (18/207) 20 (28/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Birthweight 5th percentile* 3.5 (97/2786) 4.8 (10/207) 10.7 (15/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Abruptio placentae 0.9 (24/2792) 1.9 (4/207) 3.6 (5/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
Eclampsia 0.03 (1/2792) 0 0.7 (1/140) .01
................................................................................................................................................................................................................................................................................................................................................................................
Spontaneous preterm delivery ( 35 weeks of gestation) 1.5 (41/2787) 1.9 (4/207) 3.6 (5/140) NS
................................................................................................................................................................................................................................................................................................................................................................................
Spontaneous preterm delivery ( 32 weeks of gestation) 0.4 (10/2787) 0.5 (1/207) 2.2 (3/140) NS
................................................................................................................................................................................................................................................................................................................................................................................
Composite of severe neonatal morbidity 0.4 (12/2792) 1.9 (4/207) 3.6 (5/140) .001
................................................................................................................................................................................................................................................................................................................................................................................
The results are expressed as percentages and proportions. NS, not significant.
* In the absence of preeclampsia.
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FIGURE 2
Sequential use of uterine Doppler velocimetry (UADV) results and maternal plasma concentration of PlGF,
between to 22 and 26 weeks of gestation, for the identification of patients destined to develop early
onset and/or severe preeclampsia
Flow diagram for the identification of patients at risk for early onset and/or severe preeclampsia (PE), with the use of, sequentially, UADV measurement
and the determination of maternal plasma PlGF concentration.
mitogenic signal, but rather a “decoy” erodimers of VEGFR-2 and sVEGFR-1, 4.5% of the population (140/3146
receptor that prevents the binding of which makes more VEGFR-2 avail- women), contained 60% of the patients
VEGF to VEGFR-2.31 The decoy func- able for the formation of functional (22/38 women) who developed early-
tion can be performed not only by the homodimers.34,35 onset and/or severe preeclampsia.
transmembrane, but also by the soluble The results of the current study indi- The sequential determination of
isoform (sVEGFR-1).31 An additional cate that both an abnormal UADV result UADV and maternal plasma concentra-
mechanism by which sVEGFR-1 may and a maternal plasma PlGF concentra- tion of PlGF, or vice versa, identifies pa-
regulate the bioavailability of VEGF is tion of 280 pg/mL are independent tients who are at a very high risk for early
the formation of heterodimers with the factors for the prediction of the out- onset and/or severe preeclampsia. The
VEGF receptors in the cell surface, which comes. The predictive value of an abnor- flow diagrams in Figures 2 and 3 indicate
abolishes their signal transduction.33 mal UADV between 22 and 26 weeks of that centers favoring the use of UADV
Thus, sVEGFR-1 is considered an anti- gestation for the occurrence of pre- first can obtain the same results if the de-
angiogenic factor. eclampsia and early onset preeclampsia termination of maternal plasma PlGF
PlGF is another ligand for VEGFR-1 in the study population is consistent concentrations is offered only to patients
that enhances the angiogenic response of with previous reports.5-8 However, this with abnormal UADV results (approxi-
VEGF.34,35 This has been proposed to be study further demonstrates that the mately 10% of the population), rather
accomplished by (1) intermolecular combination of abnormal UADV and a than the whole study population. This is
cross-talk between VEGFR-1 and maternal plasma PlGF concentration of because a maternal plasma concentra-
VEGFR-2 (transphosphorylation and 280pg/mL in the second trimester con- tion of PlGF did not contribute to the
activation of VEGFR-2 after activation of fers a much higher risk for preeclampsia identification of patients at risk for early
VEGFR-1 by PlGF); (2) PlGF displace- and early onset or severe preeclampsia onset and/or severe preeclampsia among
ment of VEGF from sVEGFR-1, which than abnormal UADV alone. (More- patients with normal UADV results.
makes more VEGF available to bind over, patients with abnormal UADV re- Among centers that may favor the deter-
VEGFR-2, and (3) PlGF homodimers sults and a plasma PlGF concentration of mination of maternal plasma concentra-
that can destabilize inactive het- 280 pg/mL, which represented only tion of PlGF followed by UADV, the
APRIL 2007 American Journal of Obstetrics & Gynecology 326.e8

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FIGURE 3
Sequential use of uterine artery Doppler velocimetry (UADV) results in the general population and maternal
plasma concentration of PlGF in patients with abnormal UADV for the identification of those destined to
develop early onset and/or severe preeclampsia
Simplified flow diagram for the identification of patients at risk for early onset and/or severe preeclampsia (PE), with the use of UADV followed by
maternal plasma PlGF determinations. The asterisk denotes that data for patients with normal UADV were combined, regardless of the plasma PlGF
concentration.
identification of patients at risk for early ditional studies, with larger sample sizes, recent reports that the elevation of this
onset and/or severe preeclampsia can be may be required to determine the risk of antiangiogenic factor occurs rather late
accomplished if UADV is offered only to spontaneous preterm birth among pa- in the course of the disease (approxi-
those with a plasma concentration of tients with abnormal UADV results and mately 5 weeks before the clinical pre-
PlGF of 280 pg/mL. However, this will a low PlGF concentration in the second sentation of preeclampsia).13,14 We did
require offering UADV to about one- trimester. not determine the maternal plasma con-
half of the population. sVEGFR-1 has been implicated re- centration of sVEGFR-1 among patients
It is noteworthy that patients with ab- cently in the pathophysiologic condition with normal UADV results, given that
normal UADV results and a plasma PlGF of preeclampsia.11,18,39 Indeed, clinical sVEGFR-1 did not improve the diagnos-
concentration of 280 pg/mL also had a and experimental evidence indicates that tic indices of an abnormal UADV (Fig-
higher proportion of spontaneous pre- a high maternal plasma concentration of ure 1).
term delivery than patients with normal sVEGFR-1 in patients with preeclampsia An abnormal UADV result between 22
UADV results and those with abnormal is associated with a reduction in the bio- and 26 weeks of gestation is considered
UADV results and a PlGF concentration availability of the free form of VEGF and to be a surrogate marker of chronic
of 280 pg/mL. However, the difference PlGF,39 with the subsequent endothelial uteroplacental ischemia. Evidence in fa-
did not reach statistical significance. This cell dysfunction. The observation that a vor of this view includes the following
observation is consistent with a growing maternal plasma concentration of observations: (1) the embolization of the
body of evidence showing that chronic sVEGFR-1 among patients with abnor- uterine arterioles and spiral arteries with
uteroplacental ischemia may represent mal UADV results were of limited value Gelfoam particles in pregnant animals
the mechanism of disease in a subset of in the prediction of early onset and/or reduced the uterine blood flow and in-
patients with preterm delivery.36-38 Ad- severe preeclampsia is consistent with creased the uterine artery pulsatility in-
326.e9 American Journal of Obstetrics & Gynecology APRIL 2007