Preterm Birth

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Preterm Birth Preterm Labor

• Julia Timofeev
• July 25, 2007
• University of Virginia

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Definition

• Preterm Birth
• Before 37 weeks
• Preterm Labor
• Contractions and cervical change before 37 weeks

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Why do we care?

• Incidence
• 12 of births in US
• 2 before 32 weeks
• Significance
• 2nd leading cause of infant mortality
• 50 of deaths occurred among the 1.5 of infants
  lt1500g, and 70 of deaths occurred among the 7
  of infants lt2500g
• 35 of all US health care spending goes to care
  for preterm infants
• Among 26wk survivors 60 disability
• Among 31wk survivors 30 disability

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Where do premies come from?

• 50 due to PTL
• 30 due to PPROM
• 20 from medical interventions

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Causes for preterm birth
30-50
10-30
8-9
5-40
2-4
12
6-9
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Pathogenesis of PTL

• Activation of maternal or fetal HPA axis
• Infection
• Decidual hemorrhage
• Pathological uterine distention

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HPA axis activation

• Increased release of corticotropin-releasing
  hormone (i.e. placental clock)
• Increased release of fetal pituitary ACTH
  secretion stimulates production of placental
  estrogenic compounds that activate myometrium and
  initiate labor
• CRH enhances PGD production by amnion, chorion
  and decidua

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Inflammation

• Clinical and subclinical chorioamnionitis are
  much more common in preterm deliveries
• Response is characterized by the presence of
  activated PMNs and macrophages that induce
  proinflammatory mediators such as cytokines and
  matrix metalloproteinases

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Infection

• Some bacteria
• Pseudomonas
• Staph
• Strep
• Enterobacter
• Bacteroides
• can produce proteases, collagenases and
  elastases that can degrade fetal membranes

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Decidual hemorrhage

• bleeding from decidual Vaginal hemorrhage is
  associated with high risk of PTL and PPROM
• VB in more than one trimester increases risk of
• PPROM x 7
• PTL x 3

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Uterine distention

• Multiple gestation
• Polyhydramnios
• Enhanced stretching of myometrium induces
  formation of gap junctions, upregulation of
  oxytocin receptors and production of
  prostaglandins

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Whos at risk?

• Placental pathology
• Placenta previa
• Abruption
• Vaginal bleeding
• Infection
• STDs
• Systemic infections
• Pyelonephritis
• Bacteriuria

• Cervical factors
• h/o cervical surgery
• Cervical insufficiency
• Uterine distention
• Multiple gestation
• Polyhydramnios
• Uterine anomaly or fibroids

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Risk factors for preterm birth

• Miscellaneous
• Previous preterm delivery
• Smoking
• Substance abuse

• Fetal factors
• Congenital anomaly
• Growth restriction
• Stress
• Socioeconomic factors
• Occupational hazards

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How short is too short
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Did you know

• Rate of preterm birth in African-Americans is
  significantly higher
• It is the leading cause of neonatal death (PTB
  and low birth weight)
• PTB in Hispanic Americans is only slightly
  increased over Caucasian population
• Women who change their partner between 2
  pregnancies are twice as likely to deliver
  preterm

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Risk of PTB

• Induced abortion
• OR 1.89, 2.66, and 2.03 w/ 1, 2, or gt3 previous
  pregnancy terminations
• Delayed ovulation (prolonged follicular phase)
• OR 1.5
• Interpregnancy interval
• Short interval inc risk

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More interesting factoids

• Genotypes
• Male infants maternal immune rxn?
• Periodontal disease
• ? Seeding of the placenta
• Malaria
• Bad treat it
• Anemia
• lt9.5 at 12 wks ? OR 1.68

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To treat or not to treat

• Yeast
• Treat it
• BV
• Treat it
• Trich
• Treat if symptomatic

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How do we find those at risk?

• Prediction of PTL/delivery
• Fetal Fibronectin
• Cervical Length
• CRH
• AFP and HCG
• Alk phos

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Fetal Fibronectin

• Trophoblast Glue
• Promotes cellular adhesion at uterine-placental
  and decidual-fetal membrane interfaces
• Before collection
• Intact membranes?
• CVX lt3cm?
• GA 24-34 wks?
• Intercourse/cvx check/bleeding last 24 hrs?
• Collect from posterior fornix

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FFN

• - FFN
• Negative predictive value of 99
• FFN
• Positive predictive value of 13-30
• 99.5 of symptomatic women with
• negative FFN are undelivered at 7 days
• 99.2 of symptomatic women with
• negative FFN are undelivered at 14 days

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Can we prevent it?

• Supplemental progesterone
• 17OHP start 2nd tri, continue until 36 weeks if
  prior delivery before 34 wks
• QUIT SMOKING
• Just say NO! (especially to cocaine)
• Cervical cerclage (for cvx insufficiency)
• Diagnose infection
• Asymptomatic bacteriuria, BV, GC, chlam

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What do we do in real life?

• Triage evaluation
• CEFM/Toco
• SSE - ?ROM, ?VB. Collect FFN
• Collect GC/Chlamydia cultures
• Collect GBS culture
• Cervical exam
• Check UA/Urine cx

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Dx PTL now what?

• While in the hospital
• CEFM/toco
• Yeah baby, steroids!
• BMTZ 12mg IM Q24 x 2 doses
• Antibiotic prophylaxis for GBS
• PCN, Cefoxetin, Clinda, Vanc
• Tocolysis
• PNV/Colace/FeSO4/SCDs

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Dx PTL now what?

• Tocolysis inhibit myometrial contractility
• Magnesium
• Terbutaline
• Indocin
• Nifedipine
• Contraindications to tocolysis
• IUFD, lethal fetal anomalies, NRFHT
• Severe IUGR, chorio, hemorrhage
• Severe pre-e/eclampsia

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Tocolytics
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Corticosteroids rule!

• Why?
• Reduce the risk of neonatal RDS, IVH, NEC, and
  mortality by 50 (FIFTY!)
• Benefit observed 18 hours after 1st dose, max
  benefit _at_ 48 hours
• Give 24-34 wks (?24-32wks if PPROM)
• How?
• Enhance maturation of lung architecture
• Induce lung enzymes resulting in biochemical
  maturation

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Cervical cerclage

• For cervical insufficiency which complicates
  0.1-2 of all pregnancies and is responsible for
  20 of late 2nd trimester losses
• Prophylactic cerclage 12-14wks
• Rescue cerclage when cvx changes already
  detected

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Cerclage
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Questions for you

• 27yo G2P0010 _at_ 31 wks presents for her New OB
  visit in triage c/o CTX. Initial evaluation
  includes
• A. Admonishing the pt for late PNC
• B. FFN, GC/Chlam, UA/UCx
• C. GBS cx
• D. Wet prep
• E. Cvx check
• F. B-E
• G. All of the above

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One more question

• Pts cvx is 2/75/hi and then 3/90/0 in 2 hrs, you
  notice her FH is SgtD and US reveals twins of
  course! FFN is . CTX continue despite IVF. What
  awaits the pt in the near future?
• A. Delivery
• B. PCN
• C. Tocolysis
• D. Stick in the arm for BMTZ administration
• E. More eye rolling and SW consult
• F. All of the above