This document discusses preterm labor and birth. It defines preterm birth as birth before 37 weeks of gestation. Between 28-37 weeks, organ systems like the lungs continue maturing and developing. Common risk factors for preterm birth include a previous preterm delivery, multifetal gestation, cervical surgery, smoking, and short interpregnancy intervals. The document outlines criteria for diagnosing preterm labor and discusses treatments like tocolytics and corticosteroids which can help delay delivery and improve neonatal outcomes. Complications of prematurity in infants are also reviewed.

1. PRETERM LABOR
AND BIRTH
FAHAD ZAKWAN

2. DEFINITION
• Preterm birth is birth before a gestational age of 37 complete
weeks.(i.e. btw 28 & 37 completed wks)
• In the normal human fetus, several organ systems mature
between 34 and 37 weeks, and the fetus reaches adequate
maturity by the end of this period.
• One of the main organs greatly affected by premature birth
is the lungs

4. RISK FACTORS FOR PTD
• Previous PTB
• Multiple gestation
• Polyhydramnios
• Uterine anomalies
• Infection
• Placental pathology
• Smoking
• Substance abuse
• Maternal age extremes
• Anemia
• Low BMI
• Hx cervical surgery
• Hx 2nd TM loss
• Severe stressors
• Short interpregnancy interval

5. History of preterm
birth
•odds ratio 5.1for
delivery <34 wks
•increase risk of <37
wk birth from 9% to
22%
Multifetal gestation
•preterm birth
incidence (<37 wks)
50 % in twins, higher
in triplets

6. Cervical surgery
•cervical conization OR
3.23, CI 2.29-4.55
•cryotherapy, laser
vaporization, laser
minicone, LEEP not
associated with
preterm birth
Uterine malformation
•unicornuate uterus
17% risk of preterm
birth
•large uterine fibroid
>5cm may increase
preterm birth risk

7. Smoking
• daily consumption of
• 1-9 cig OR 1.1(1.1-1.2)
PTB<36wks and
OR1.3(1.2-1.5) PTB<32
wks
• >10 cig/d OR 1.4(1.3-1.4)
PTB<36 wks and OR 1.6
PTB<32wks
Substance abuse
•hard to separate from
other risk factors
•cocaine positive urine
samples gives 3-6 fold
increased risk preterm
labor

8. Interpregnancy interval
• in two separate
epidemiologic studies,
birth interval <18 months
or >59 months increases
risk of preterm birth than
birth intervals between
18 and 59 months.
Others:
•physical activity (+/-),
socioeconomic status,
anemia, adolescence,
prior terminations,
periodontal disease,
delayed ovulation.
•No role for diet or
paternal risk factors

9. • History of preterm delivery
• History of diethylstilbestrol exposure
• History of second trimester abortion
• Young age<18 years
• Low socioeconomic status
• Acute or chronic systemic disease
• Trauma
• Abdominal surgery during pregnancy
• Infections: Untreated syphilis, Neisseria gonorrhoeae, asymptomatic group B streptococcus, acute
pyelonephritis, cervicovaginal infections
• Smoking
• Drug abuse
MATERNAL FACTORS

10. •Overdistention of cavity: multiple gestation,
polyhydramnios
•Abnormal cavity: uterine anomaly, fibroids
•Foreign body: intrauterine device
•Cervical incompetence
•Trauma to cervix
UTERINE & CERVICAL CAUSES

11. •Faulty placentation: placenta previa,
placental abruption
•Genetic abnormality
•IUFD
•PROM
•Iatrogenic-50%
OTHER CAUSES

12. • 20%-25% Preterm deliveries don’t follow preterm
labor
• Elective delivery:
• Severe preeclampsia
• Non reassuring fetal heart rate
OTHER CONSIDERATION

13. Preterm Birth
•Spontaneous preterm labor 30-50%
•Multiple gestation 10-30%
•PPROM 5-40%
•Preeclampsia/eclampsia 12%
•Antepartum bleeding 6-9%
•Fetal growth restriction 2-4%
•Other 8-9%

14. Survival in Premature Infants
• 26 wks – 80%
• 27 wks – 90%
• 28-31 wks – 90 to 95%
• 32-33 wks – 95%
• 34-36 wks – approaches term
survival rates

15. • ↑Survival rate with ↑gestational age and birth weight
• 70%-80% survival in infants weighing 750 to 1000 gms
• High mortality rate with weight < 750 gms
• 24 weeks-Survival 43%
• 25 weeks-Survival 74%
• 26 weeks-Survival 83%
• Greatest gain achieved by prolonging pregnancy beyond 24
weeks gestation
NEONATAL MORTALITY

18. • Survival exceeds 90% by 30 weeks gestation
• 90% Preterm births: 30-36 weeks gestation
• Morbidity primary concern at this gestational age
• ↓ Morbidity from RDS > 36 weeks gestation
• ↓ Morbidity from IVH (grade III and IV) > 27 weeks gestation
• ↓ Morbidity from necrotizing enterocolitis and patent
ductus arteriosus > 32 weeks gestation
NEONATAL MORBIDITY

19. PATHOGENESIS
4 PRIMARY AETIOLOGIES RECOGNISED
1. Premature activation of maternal or fetal
HPA axis
2. Decidual hemorrhage
3. Inflammation/infection
4. Pathological uterine distention

20. HPA axis activation
• in the mother can result from stress, psychological or physical
• in the fetus can result from stressors such as uteroplacental
vasculopathy, preeclampsia, nonreassuring heart rate patterns,
and hypoxemia.
• Markers of HPA activation are corticotropin releasing hormone
and maternal estrogens (primarily synthesized by the fetus!)
• clinical assays for serum CRH and salivary estriol have been
validated but don’t add to clinical diagnosis

21. INFECTION
• including bacterial vaginosis, chlamydia, GC, group B strep,
ureaplasma vaginally or chorioamnionitis
• increase risk for spontaneous preterm birth through inflammatory
mediators such as interleukin-6 (IL-6) or prostaglandin E2 or F2.
• Treatment of asymptomatic bacteriuria, bacterial vaginosis in high risk
patients, and gonorrhea reduces risk of preterm birth
• Treatment of GBS, chlamydia, or syphilis is aimed at preventing
transmission, as preterm birth risk is not reduced

22. DECIDUAL HEMORRHAGE
•increases risk of PTL and premature
rupture of membranes (PROM)
•vaginal bleeding in more than one
trimester increase risk of PROM
sevenfold.

23. UTERINE DISTENSION
•It is due to multifetal gestation, polyhydramnios,
and others increase risk of preterm birth
•note on cervical incompetence: dilation of cervix
unrelated to labor. Likely due to one of these
four processes at a time when myometrium
resistant to uterotonics.

24. Complications of Prematurity
• RDS
• IVH
• Feeding difficulties/NEC
• Apnea
• PDA
• Infection
• Jaundice
• Hypothermia
• Neurobehavioral
• ROP
• Anemia

25. Criteria: PRETERM LABOUR
Clinical diagnosis with all of the following
GESTATION AGE: ≥ 28 wks  37 wks
CONTRACTIONS ≥ 3 in 30 minutes
CERVIX DILATATION: ≥ 2 cm
EFFACEMENT: ≥ 80%

26. Augment your diagnosis with cervical length by
ultrasound following data from 24 and 28 week
series
•10th% = 25mm (20 to 30
wks gestation)
•80-100% of women who
deliver early have cervix
<30mm
•15 mm or less = 50%
delivery rate within one
week

27. Augment your diagnosis with
fetal fibronectin:
• requires intact fetal membranes, cervical dilatation < 3cm,
gest age between 24 wks and 35 wks.
• Collected from posterior fornix or cervical os during
speculum exam
• false positives can result from manipulation of the cervix--
digital or ultrasound exam, or coitus within 24 hrs.--or from
vaginal lubricants or medications
• fFN concentration>50 ng/ml considered positive.

28. Fetal Fibronectin
•99% negative predictive
value for delivery within 2
wks
•Positive predictive value
worse, about 30%
•22 to 35 weeks
•Sample collection issues

29. • Physical examination
• Intravenous hydration
• Bed rest
• Fetal heart rate monitoring
• Ultrasonography for gestational age and weight
• Amniocentesis for fetal lung maturity and to rule out
infection
• Speculum examination to rule out PPROM
ASSESSMENT AND THERAPY

30. Goals of Treatment of PTL
Tocolytics
•Often halts contractions only temporarily
•Allow 48 hr. + for steroids to be given
•Allow for transport to delivery location with
NICU capability
•Allow for correction of reversible causes

31. Review meds
Steroids
• Reduce incidence of RDS, IVH, NEC, sepsis, and mortality by about
50%
• administer to all women at high risk for preterm delivery unless
‘immediate’ (<1 hour) delivery is anticipated
• GA 24-34 weeks with intact membranes
• PPROM: 24-32 weeks GA
• betamethasone 12 mg IM q 24 hrs. x 2 doses or dexamethasone
6mg IM q 12 hrs. x 4

32. •Reduced incidence of respiratory distress
syndrome
•Reduced incidence of intraventricular
hemorrhage
•Reduction of neonatal morbidity and mortality
benefits of steroid before preterm
delivery

33. Tocolysis
• Tocolysis 24-34 weeks, earlier for elective cerclage or abdominal
surgery
• contraindications include:
• IUFD,
• lethal fetal anomaly,
• nonreassuring fetal assessment,
• severe IUGR, chorioamnionitis,
• maternal hemorrhage with hemodynamic
instability,
• severe preeclampsia or eclampsia

34. • β-adrenergic agents:
Ritodrine*
Terbutaline
• Magnesium sulfate
• Prostaglandin synthetase inhibitor:
Indomethacin
• Calcium channel blockers:
Nifedipine
* Ritodrine is only FDA approved tocolytic, however, terbutaline, magnesium
sulfate, nifedipine and indomethacin are widely used in US.
TOCOLYTIC AGENTS:

35. Tocolytics…..
Nifedipine
•Efficacy based on comparison to ritodrine or any
agent, no placebo controlled trials
•dose 30 mg orally followed by 20 mg orally in 90 min
•mild side effects make it number one for
maintenance, 10-30 tid or ER 60-90/d

36. Tocolysis…..
• Beta agonists (ritodrine, terbutaline)
• Tachycardia, hypotension, tremor, palpitations, chest discomfort,
hypokalemia, hyperglycemia
• Magnesium sulfate
• Nausea, flushing, fatigue, diaphoresis, loss of DTRs, respiratory depression,
cardiac arrest
• Indomethacin
• Maternal GI SE, premature closure of ductus, oligohydramnios
• Atosiban
• Possible increase in fetal/neonatal morbidity/mortality; not available in US

37. Terbutaline
• prolongs pregnancy in RCT’s, insignificant trend towards
reduction in low birth weight and RDS
• contraindicated in women with heart disease due to
inotropy
• iv dose 2.5-5 micrograms/min, increase q 20-30 minutes to
max of 25 micrograms/minute
• SQ dose .25 mg q 20-30 minutes x 4 doses
• watch pulmonary edema, myocardial ischemia in moms

38. Magnesium sulfate
• despite lack of evidence that pregnancy is prolonged, used locally as
more efficacious than terbutaline
• toxicity related to level
• 8-10 loss of DTR’s
• 10-15 respiratory paralysis
• 15-20 cardiac arrest
• Contraindicated in myasthenia gravis
• dose 4-6 gm. IV load over 20 min,
• follow with infusion 2-4 gms/hr

39. Indocin
•efficacy based on small trials
•fetal side effects of oligo and premature closure of
ductus arteriosus(DA) limit use
•dose 50-100 mg loading dose, followed by 25 mg
QID
•if given >48 hours, evaluate sonographically for oligo
and narrowing of DA at least weekly

40. • ABSOLUTE:
• Fetal death
• Fetal anomalies incompatible with life
• Fetal distress warranting immediate delivery
• Chorioamnionitis / fever of unknown origin
• Severe hemorrhage
• Severe chronic HTN and/or PIH
• RELATIVE:
• Cervical dilation > 4 cm
• Ruptured membranes
CONTRAINDICATIONS TO TOCOLYTIC
THERAPY

41. Management after Tocolysis
•If maternal and fetal conditions are stable,
can be managed at home
•Avoid excessive physical activity; most
advocate pelvic rest
•Continued tocolytics have not shown
definite benefit

42. PREVENTION OF PTB
•Reduce/eliminate risk factors, if possible
•Not proven to be effective:
•bed rest,
•home uterine monitoring,
•prophylactic tocolytics,
•prophylactic antibiotics,
•abstinence

43. PREVENTION OF PRETERM BIRTH
•Supplemental progesterone
•Women with previous spontaneous preterm
delivery at less than 34 weeks gestation
•Weekly 17OHprogesterone IM or daily vaginal
progesterone suppositories
•Start at 16-20 wks gestation, continue through
36 weeks

44. Want some more???????????

45. • During labor and delivery, preterm infant at high risk of acidosis and
has high incidence of intracranial hemorrhage
• High incidence of CD due to fetal distress
• Preterm infant more sensitive to depressant effects of analgesic and
anesthetic drugs.
• Regional anesthesia technique of choice to avoid depressant effects
of anesthetic drugs.
• Epidural prevents precipitous vaginal delivery and rapid
decompression of vulnerable fetal head
ANESTHETIC CONSIDERATIONS

46. • Ritodrine and terbutaline commonly used agents
• May delay delivery for 24-48 hrs; however, not in substantial prolongation of
pregnancy
• Contraindicated in severe cardiac or pulmonary disease
• Reported incidence of side effects vary from 0.54% to 9% as per different studies
• Side effects include hypotension, tachycardia, cardiac arrhythmias, myocardial
ischemia, pulmonary edema, hyperglycemia, hypokalemia and fetal tachycardia
• Side effects dose related
• Consider delaying administration of anesthesia where feasible until maternal side
effects have subsided
BETA-ADRENERGIC AGONISTS

47. • Extensive experience for use of seizure prophylaxis in preeclamptic women
• Little scientific evidence of efficacy of MgSO4 for tocolysis
• Many clinicians consider MgSO4 to be tocolytic of choice in patients at high risk
of bleeding (P. Previa)
• Less frequent and less severe side effects than β-adrenergic agents
• Side effects include chest pain, palpitations, nausea, transient hypotension,
blurred vision, sedation and pulmonary edema
• Can attenuate compensatory response to hemorrhage
• Some concern about possible increase in perinatal mortality
• May increase risk of hypotension
MAGNESIUM SULFATE

48. • Loading dose 4 gm over 15-20 min
• Followed by infusion at 1-4 gm/hr
• Serum levels of 5-7 mg/dl required for tocolysis
• 8-10 mg/dl; loss of tendon reflexes
• 10-15 mg/dl: respiratory depression
• >10-15 mg/dl: cardiac conduction defects
• Potentiates both depolarizers and non-depolarizers
• Causes sedation, ↓MAC and ↓analgesic requirements
• Modest prolongation of bleeding time due to effect on platelet
aggregation by antagonizing the effects of Ca++
MAGNESIUM SULFATE

49. • Acts by inhibiting cyclo-oxygenase
• Dose: 50 mg PO followed by 25 mg PO 4-6 hr
• Limit course of therapy to less than 72 hr and administer only before 32 week
gestation to minimize neonatal side effects
• No cardiovascular side effects like other agents
• ↓ thromboxane A2 →↓platelet aggregation
• Does not necessitate assessment of coagulation status prior to regional due to
transient reversible effect on platelet function
• Can cause premature closure of ductus arteriosus in utero resulting in persistent
fetal circulation if administered after 32 weeks gestation
• Other side effects include oligohydramnios and neonatal necrotizing enterocolitis
INDOMETHACIN

50. • Reduced side effect profile compared to β-adrenergic agonists
• Some investigators suggest as first line tocolytic compared to others
• Can arrest labor for 48 hrs or longer
• Can be administered orally or sublingually
• Dose: 10-20 mg PO every 4-6 hours
• More effective with fewer side effects than
β-adrenergic agents and better neonatal outcome
• However, adverse fetal effects as per some animal studies
• Usually mild maternal side effects like flushing
• Potential to cause vasodilatation, hypotension, myocardial depression and
conduction defects when used in combination with volatile agents
NIFEDIPINE