OBSTETRIC TOPICS; PRETERM LABOR, PROM AND PREPROM

1. By; JOYCE F. MWATONOKA
MD4
Sept 2016

2.  Preterm infants are those delivered before 37
completed weeks
 Early preterm; <33 weeks
 Late preterm; between 34 and 36 completed
weeks. 70% of all preterm births.
 Early term; 37 wk to 38wk 6days
 Term; 39 weeks 0 days to 40 weeks 6 days.
Infant mortality is lower than at any other
time in human gestation

3.  Rate of spontaneous preterm births has been
decreasing, but there has been a significant
rise of induced preterm births
 Various morbidities, largely due to organ
system immaturity, are significantly increased
in infants born before 37 weeks’ gestation
compared with those delivered at term

4. (1) Spontaneous unexplained preterm labor with
intact membranes
(2) Idiopathic preterm premature rupture of
membranes (PPROM)
(3) Delivery for maternal or fetal indications,
and
(4) Twins and higher order multifetal births.

5.  Of all preterm births, 30 to 35 percent are
indicated, 40 to 45 percent are due to
spontaneous preterm labor, and 30 to 35
percent follow preterm membrane rupture

6.  Mechanisms that lead to the onset of preterm
labor are complex and multifactorial, but it is
likely to occur as a result of the concomitant
activation or a cascade of the following
events;
◦ Functional progesterone withdrawal
◦ Increase in corticotrophin-releasing hormone
◦ Premature decidual activation
◦ Increased prostaglandin production
◦ Oxytocin initiation
◦ Increased cytokine production

7.  Multifetal pregnancy; Uterine stretch
increases gap junction proteins, PGs
synthesis, receptors for oxytocin and specific
contraction associated proteins (CAPS).
 Hydramnios
 Placental infarction,
 IDIOPATHIC

8.  Intrauterine infections; trigger preterm labor by
activation of the innate immune system. In this
hypothesis, microorganisms elicit release of
inflammatory cytokines such as interleukins and
TNF-α, which in turn stimulate the production of
prostaglandin and/or matrix-degrading
enzymes. Prostaglandins stimulate uterine
contractions, whereas degradation of
extracellular matrix in the fetal membranes leads
to preterm rupture of membranes.
 It is estimated that 25 to 40 percent of preterm
births result from intrauterine infection.

9.  Fetal anomalies; In a secondary analysis of
data from the First- and Second-Trimester
Evaluation of Risk (FASTER) Trial, it was found
that birth defects were associated with
preterm birth and low birthweight (Dolan,
2007

10. Prior Preterm Birth
 A major risk factor for preterm labor is prior
preterm delivery
 Increases risk 3 folds

11. Threatened Abortion
 Vaginal bleeding in early pregnancy is
associated with increased adverse outcomes
later
 Both light and heavy bleeding were
associated with subsequent preterm labor,
placental abruption, and subsequent
pregnancy loss before 24 weeks
 Also anemia

12.  Uterine anomalies: Cervical incompetence,
malformation of uterus
 Cigarette smoking, inadequate maternal
weight gain, and illicit drug use have
important roles in both the incidence and
outcome of low-birthweight neonates (Chap.
12, p. 253).
 Overweight and obese mothers have an
elevated risk of preterm birth

13. Work and physical activities
 Conflicting results (Goldenberg, 2008).
 There is some evidence, however, that
working long hours and hard physical labor
are probably associated with increased risk of
preterm birth (Luke, 1995).

14.  As discussed on page 837, psychological
factors such as depression, anxiety, and
chronic stress have been reported in
association with preterm birth

15. Genetic Factors
 The recurrent, familial, and racial nature of
preterm birth has led to the suggestion that
genetics may play a causal role.
 As discussed on page 839, several such
studies have also implicated
immunoregulatory genes in potentiating
chorioamnionitis in cases of preterm delivery
due to infection

16. Interval between Pregnancies
 Short intervals between pregnancies have
been known for some time to be associated
with adverse perinatal outcomes.
 Conde-Agudelo and colleagues (2006)
reported that intervals < 18 months and > 59
months were associated with increased risks
for both preterm birth and small-for
gestational age newborns

17.  Severe maternal illness as a result of
infections like acute pyelonephritis, diarrhea,
acute appendicitis and toxoplasmosis,
autoimmune diseases, and gestational
hypertension also increases preterm labor
risks
 These diverse processes culminate in a
common end point, which is premature
cervical dilatation and effacement and
premature activation of uterine contractions.

18.  Preterm labor is primarily diagnosed by
symptoms and physical examination.
 Sonography is used to identify asymptomatic
cervical dilation and effacement.

19. (1) Regular uterine contractions with or without
pain (at least one in every 10 minute);
(2) Dilatation (> 2 cm) and effacement (80%) of
the cervix;
(3) Length of the cervix (measured by TVS) <
2.5 cm and funneling of the internal os (see
p. 169)
(4) Pelvic pressure, backache and or vaginal
discharge or bleeding.
 It is better to overdiagnose preterm labor
than to ignore the possibility of its presence.

20.  Full blood count
 Urine for routine analysis, culture and
sensitivity
 Cervicovaginal swab for culture
 Ultrasonography for fetal well being, cervical
length and placental localization
 Serum electrolytes and glucose levels when
tocolytic agents are to be used

21. (1) Glucocorticoids to the mother to reduce
neonatal RDS, IVH and NEC. Betamethasone
(Betnesol) 12 mg IM 24 hours apart for two
doses or dexamethasone 6 mg IM every 12
hours for 4 doses is given
(2) Antenatal transfer of the mother with fetus
in utero to a center equipped with NICU
(3) Tocolytic drugs (see p. 507) to the mother
for a short period unless contraindicated eg;
PG synthase inhibitors (indomethacin),
MgSO4, Ca channel blockers, Oxytocin
receptor antagonists (Atosiban), progesterone

22. (4) Antibiotics to prevent neonatal infection
with Group B Streptococcus (GBS)
(5) Careful intrapartum monitoring, minimal
trauma and presence of a neonatologist
during delivery
(6) Vaginal delivery is preferred, unless
otherwise indicated for cesarean birth

23.  If fetus is not compromised, the maternal
condition remains good and membranes are
intact;
 Bed rest; preferably in left lateral position
 Adequate hydration
 Prophylactic cervical circlage; for women with
prior preterm birth and short cervix in the
present pregnancy
 Tocolytic agents

24.  Maternal: Uncontrolled diabetes,
thyrotoxicosis, severe hypertension, cardiac
disease, hemorrhage in pregnancy, e.g.
placenta previa or abruption.
 Fetal: Fetal distress, fetal death, congenital
malformation, pregnancy beyond 34 weeks.
 Others: Rupture of membranes,
chorioamnionitis, cervical dilatation more
than 4 cm

25.  NB; The American College of Obstetricians
and Gynecologists (2012a) has concluded
that tocolytic agents do not markedly prolong
gestation but may delay delivery in some
women for up to 48 hours. This may allow
transport to a regional obstetrical center and
permit time for corticosteroid therapy.

26.  Braxton Hicks contractions; irregular,
nonrhythmical, and either painful or painless
 Placental abruption
 Urinary; acute cystitis, pyelonephritis,
nephrolithiasis
 Gatrointestinal; Constipation

27. 1. Cervical Cerclage
 There are at least three circumstances when
cerclage placement may be used to prevent
preterm birth. Two are done prophylactically, and
a third is done for treatment. The first
prophylactic cerclage is used in women who have
a history of recurrent midtrimester losses and
who are diagnosed with cervical insufficiency.
The second prophylactic cerclage is for women
identified during sonographic examination to
have a short cervix. The third indication is
“rescue” cerclage, done emergently when cervical
incompetence is recognized in women with
threatened preterm labor.

28. 2. Prophylaxis with Progestin Compounds (17-
hydroxyprogesterone)
 Progesterone levels in most mammals fall rapidly
before the onset of labor. This is termed
progesterone withdrawal and is considered to be
a parturition-triggering event. During human
parturition, however, maternal, fetal, and
amnionic fluid progesterone levels remain
elevated with no decline. It has been proposed
that human parturition involves functional
progesteronewithdrawal mediated by decreased
progesterone activity of progesterone receptors
(Ziyan, 2010). It follows conceptually that the
administration of progesterone to maintain
uterine quiescence may block preterm labor.

29. 3. Geographic-Based Public Health-Care
Programs
 A well-organized prenatal system results in a
decreased preterm birth rate in high-risk
indigent populations.

30.  PROM; Spontaneous rupture of the
membranes any time beyond 28th week of
pregnancy but before the onset of labor.
 When rupture of membranes occur beyond
37th week but before the onset of labor it is
called term PROM
 and when it occurs before 37 completed
weeks, it is called preterm PROM.

31.  Rupture of membranes for > 24 hours before
delivery is called prolonged rupture of
membranes.
 PROM occurs in approximately 10% of all
pregnancies.

32. (1) Increased friability of the membranes;
(2) Decreased tensile strength (stretching) of
the membranes;
(3) Polyhydramnios;
(4) Cervical incompetence;
(5) Multiple pregnancy;

33. (6) Infection—Chorioamnionitis, urinary tract
infection and lower genital tract infection
(7) Cervical length < 2.5 cm
(8) Prior preterm labor
(9) Low BMI (< 19 kg/m2).

34.  A history of vaginal leakage of fluid, either as
a continuous stream or as a gush
 Often confused with :
(a) Hydrorrhea gravidarum—a state where
periodic watery discharge occurs probably
due to excessive decidual glandular secretion;
(b) Urine incontinence specially in the later
months
(c) Heavy candidiasis

35. 1. Sterile speculum examination to visualize
gross vaginal pooling of amniotic fluid, clear
fluid from the cervical canal, or both.
2. To examine the collected fluid from the
posterior fornix (vaginal pool) for:
(a) Detection of pH by litmus or Nitrazine
paper. The pH becomes 6–6.2 (Normal
vaginal pH during pregnancy is 4.5–5.5
whereas that of liquor amnii is 7–7.5).
Nitrazine paper turns from yellow to blue at
pH > 6

36.  Blood, semen, antiseptics, or bacterial
vaginosis, however, are all also alkaline and
can give false positive results.
(b) To note the characteristic ferning pattern
when a smeared slide is examined under
microscope (fern test); due to crystallization
of NaCl on mucus fibers under high estrogen
concentration

38. (c) Centrifuged cells stained with 0.1% Nile blue
sulfate showing orange blue coloration of the
cells (exfoliated fat containing cells from
sebaceous glands of the fetus)
 Confirmation of ruptured membranes is
usually accompanied by sonographic
examination to assess amnionic fluid volume,
to identify the presenting part, and if not
previously determined, to estimate GA

39.  Full blood count
 Urine for routine analysis and culture
 High vaginal swab for culture

40.  Vaginal pool/amniosentesis for estimation of
Phosphatidyl glycerol and L:S ratio (Lecithin-
spingomyelin ratio), for assessment of fetal
lung maturity
 Ratio is 1 upto 32 wk GA, then Lecithin
increases while shingomyelin remains nearly
the same
 Ratio of 2 or more at 35wk indicates lung
maturity, <1.5 ass/c high risk of infant RDS
 Centrifuge at 1000 rpm for 3-5min, then TLC
(thin layer chromatography)

41.  Shake test or Bubble test (Clement’s)
 Foam Stability Index (FSI); FSI>47 virtually
excludes the risk of RDS
 Saturated phosphatidyl choline > 500 ng/mL
indicates pulmonary maturity
 Fluorescence polarization; Presence of
55mg of surfactant per gram of albumin
indicates fetal lung maturity

42.  Amniotic fluid optical density at 650 mµ
greater than 0.15 indicates lung maturity
 Lamellar body count > 30,000/µL indicates
pulmonary maturity
 Orange colored cells cells > 50% suggests
pulmonary maturity.
 Amniotic fluid turbidity due to vernix caseosa

43.  The time from PPROM to delivery is inversely
proportional to the gestational age when
rupture occurs (Carroll, 1995).
 Very few days were gained when membranes
ruptured during the third trimester compared
with mid-pregnancy

44.  Hospitalization
 Term PROM: If the patient is not in labor and
there is no evidence of infection or fetal distress,
she is observed carefully, in the hospital
 Generally in 90% of cases spontaneous labor
ensue within 24 hours. If it does not, induction of
labor with oxytocin is commenced forthwith
 Cesarean section is performed with obstetric
indications
 Expectant Management; increased incidence of
fetal neurological damage and clinical
chorioamnionitis

45.  Preterm PROM: The main concern is to
balance the risk of infection in expectant
management (while pregnancy is continued)
versus the risk of prematurity in active
intervention. Ideally the patient should be
transferred with the “fetus in utero” to an unit
able to manage preterm neonates effectively

46.  If the gestational age is 34 weeks or more,
perinatal mortality from prematurity is less
compared to infection
 Labor generally starts spontaneously within
48 hours, otherwise induction with oxytocin
is instituted
 Presentation other than cephalic merits
cesarean section

47.  When gestational age is less than 34 weeks,
conservative attitude generally followed in
absence of any maternal or fetal indications
 On rare occasion with bed rest, the leak seals
spontaneously and pregnancy continues

48. Corticosteroids to Accelerate Fetal Lung
Maturity
 Singledose therapy is recommended from 24
to 32 weeks
 There is no consensus regarding treatment
between 32 and 34 weeks
 Corticosteroid therapy is not recommended
before 24 weeks

49. Use of antibiotics: Prophylactic antibiotics are
given to minimize maternal and perinatal
risks of infection.
 Intravenous ampicillin, amoxicillin or
erythromycin for 48 hours followed by oral
therapy for 5 days or until delivery is
recommended.

50. Membrane Repair
 Tissue sealants have been used for various
purposes in medicine and have become
important in maintaining surgical hemostasis
and stimulating wound healing.
 Devlieger and colleagues (2006) have
reviewed the efficacy of sealants in the repair
of fetal membrane defects such as in preterm
ruptured membranes.

51.  Magnesium Sulfate for Fetal Neuroprotection

52.  Preterm labor and prematurity;
 Chorioamnionitis from ascending infection if
>24hrs
 Cord prolapse specially when associated with
malpresentation
 Continuous escape of liquor for long duration
may lead to dry labor
 Placental abruption
 Neonatal sepsis, RDS, IVH and NEC in preterm
PROM
 Perinatal morbidities (cerebral palsy) are high

53.  William’s 24th edition
 Dutta’s text book of obstetrics 7th edition