preterm delivery

Introduction

Delivery before 37 weeks of gestation.

Etiology

• may be associated with maternal genital tract flora
• risk factors:
  • prior preterm delivery
  • periodontal disease
  • obesity
  • cervical length <= 15 mm high risk, >= 30 mm low risk

Laboratory

• positive fetal fibronectin is a risk factor
  • vaginal fetal fibronectin is a poor predictor of spontaneous preterm birth

Diagnostic procedures

• serial transvaginal ultrasound cervical length is a poor predictor or spontaneous preterm birth

Complications

• low birth weight
• major cause of perinatal morbidity & mortality in developed nations
• retinopathy of prematurity
• cerebral palsy
• only 12% of infants born < 23 weeks of gestation & 24% of infants born at 25 weeks of gestation had normal school-age neurologic & cognitive assessment
• all measures of adverse medical & social outcomes,including job-related income, but excluding measures ofcriminality increased with decreasing gestational age
• increased risk for developing chronic kidney disease in adulthood

Management

• prophylaxis
  • early screening for bacterial vaginosis may be of benefit
  • clindamycin 300 mg BID for 5 days in the 2nd trimester may be of benefit for women with abnormal vaginal flora
  • 17-alpha-hydroxyprogesterone (Duralutin) 250 mg IM weekly beginning at 15-20 weeks of gestation in high risk women may reduce incidence of preterm delivery
  • magnesium sulfate 6 g IV bolus followed by infusion of 1-2 g hourly for 24 hours for women < 34 weeks gestation lowers risk of cerebral palsy
    • does not result in improved outcomes in children at school age
  • vaginal progesterone 200 mg QHS from 22-34 weeks gestation in high-risk women may reduce neonatal death, but does not reduce risk of premature delivery or fetal death
  • vaginal progesterone may be best strategy to prevent preterm birth
• antenatal corticosteroids
  • for mothers with preterm labor from 22-34 weeks' gestational age; 22-37 weeks' gestation
  • betamethasone (12 mg, 2 IM injections 24 hours apart) for pregnant women with single fetus 34-36 weeks 5 days of gestation likely to deliver before 37 weeks (preterm labor with intact membranes or spontaneous rupture of membranes) reduces needfor postnatal respiratory support 12% vs 14% for placebo (NNT = 35)
  • number needed to treat to prevent 1 infant death = 6 at 23-24 weeks gestation & 798 at 34 weeks gestation
  • antenatal glucocorticoids reduces composite risk of
    • severe intracranial hemorrhage or death
    • necrotizing enterocolitis or death
    • severe retinopathy of prematurity or death
  • antenatal glucocorticoids at 24-28 weeks gestation is not associated with neurodevelopmental impairment at 2 years of age
• a cervical pessary implemented in the 2nd trimester can lower risk of preterm delivery in women with a short cervix (RR=0.5)

More general terms

• labor & delivery
• pathologic process

Additional terms

• low birth weight infant (preterm infant)
• premature labor; preterm labor