Preterm labor

Background

• Defined as labor before 37 weeks (uterine ctx and cervical change)
• Increased risks to child depending on age of fetus
  • Cerebral palsy, poor lung development, cognitive delay, etc
• Can be triggered by maternal infx, stress, HTN, uncontrolled DM

Clinical Presentation

• Similar to term labor
  • Uterine contractions q 10 min (may be irregular)
  • New onset of vaginal mucus, blood, pink discharge, amniotic fluid
  • Low back ache, vaginal pressure

Differential Diagnosis

• Preterm Labor
• Placental abruption
• Placenta previa
• Vasa previa
• Uterine rupture
• Vaginal trauma

Diagnosis

• Do NOT perform digital exam in patients who present with vaginal bleeding when >20 weeks pregnant
• Start with ultrasound to assess position of cervix and r/o placenta previa
• Swabs for fetal fibernectin, Group B strep should also precede digital exam
• Proceed with digital exam if placental previa unlikely, and digital exam is urgently needed to assist patient care, such as in fetal HR decels

Management

• Fetal Heart Monitor
• U/S to assess placental position / fetal position
• Digital exam to assess cervical thickness, effacement, rupture of membranes
• CBC, Chem, Coags, U/A w/ culture, Utox (cocaine increases risk of abruption)

• Cervical length >30mm - Labor less likely
  • Observation of 6 hours might be appropriate

• Cervical length 20-30mm - Increased risk for preterm labor
  • Fetal fibernetin result can assist, if over 50ng/ml manage labor actively

• Cervical length <20mm - labor very likely
  • Manage actively

• <34 weeks
  • Betamethasone, and hospitalization
  • Tocolytics
  • Antibiotics for GBS prophylaxis if status unknown
  • Other abx only indicated in setting of active infx

• 24-32 weeks
  • Mag sulfate (neuroprotection against cerebral palsy)

Tocolysis

• Indications
  • Only if fetus would benefit from delay in delivery of 48 hrs
  • Gestational age 22wks - 34 wks
  • Transport to facility for definitive delivery
  • Delay in delivery of reversible condition possibly triggering labor (UTI/pyelo)
    • Betamethasone requires approx 48 hrs for maximal benefit for lung maturity, reducing intraventricular hemorrhage, NEC, and death
    • Tocolysis rarely effective for longer than 48 hrs
    • Does not remove underlying cause for tocolysis
• Contraindications
  • Intratuterine fetal demise / lethal anomaly
  • Maternal hemorrhage or instability
  • Intraamniotic infx
  • Severe preeclampsia or eclampsia
  • Nonreassuring fetal status
  • Contraindications to the drugs

References

UpToDate "Overview of preterm labor and birth"

UpToDate "Inhibition of acute preterm labor"