What is the initial management for a woman in preterm labour at 35 weeks of gestation?

Management of Preterm Labour at 35 Weeks of Gestation

At 35 weeks of gestation, preterm labor should generally be allowed to progress to delivery rather than aggressively treated with tocolytics, with management focused on GBS prophylaxis, antenatal corticosteroids if not previously administered, and magnesium sulfate for neuroprotection if delivery is imminent before 32 weeks (though at 35 weeks this is typically not indicated).

Initial Assessment and GBS Management

Group B Streptococcus Screening and Prophylaxis

• Obtain a vaginal-rectal swab for GBS culture immediately upon admission if no GBS screen was performed within the preceding 5 weeks 1, 2.
• Start GBS prophylaxis immediately while awaiting culture results 1, 2.
• If the patient enters true labor, continue GBS prophylaxis until delivery 1.
• If labor does not progress (false labor), discontinue GBS prophylaxis 1.
• When GBS culture results become available:
  • If positive: Continue intrapartum antibiotic prophylaxis during labor 1, 3
  • If negative: Discontinue GBS prophylaxis 1

Recommended Antibiotic Regimen for GBS

• Penicillin G: 5 million units IV initially, then 2.5-3 million units IV every 4 hours until delivery 3
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours 3
• For penicillin allergy (low-risk): Cefazolin 2 g IV initially, then 1 g IV every 8 hours 3

Rationale for Not Aggressively Treating Labor at 35 Weeks

Neonatal Outcomes at 35 Weeks

The evidence strongly supports allowing delivery at 35 weeks rather than attempting prolonged tocolysis:

• Respiratory distress syndrome (RDS) rates drop significantly from 15.0% at 34 weeks to 3.2% at 36 weeks, with most improvement occurring after 35 weeks 4.
• Nosocomial sepsis decreases from 5.0% at 34 weeks to 0% at 36 weeks 4.
• Apnea of prematurity declines from 11.7% at 34 weeks to 2.2% at 36 weeks 4.
• Hospital length of stay decreases dramatically from 16 days at 34 weeks to 4 days at 36 weeks 4.

At 35 weeks specifically, neonatal complications are substantially reduced compared to 34 weeks, making aggressive tocolysis less justified 4, 5.

Antenatal Corticosteroids

• Administer antenatal corticosteroids if delivery is anticipated and the patient has not received a prior course 1.
• Corticosteroids are recommended between 34 0/7 and 36 6/7 weeks for women at risk of preterm delivery within 7 days who have not received a prior course 1.
• This is the only antenatal intervention proven to improve neonatal outcomes, including reduced neonatal mortality, intracranial hemorrhage, necrotizing enterocolitis, and infection 6.

Magnesium Sulfate for Neuroprotection

• Magnesium sulfate is recommended for fetal neuroprotection when delivery is anticipated before 32 weeks of gestation 1.
• At 35 weeks, magnesium sulfate for neuroprotection is not indicated as the evidence supports its use only before 32 weeks 1.

Tocolytic Therapy Considerations

At 35 weeks, tocolytic therapy is generally not recommended for the following reasons:

• The primary goal of tocolysis is to delay delivery for 48-72 hours to allow corticosteroid administration and maternal transfer 6, 7.
• Evidence shows tocolytics may delay delivery briefly but have not consistently demonstrated improved neonatal outcomes 1, 6.
• At 35 weeks, the risk-benefit ratio favors allowing labor to progress given the relatively good neonatal outcomes at this gestational age 4, 5.
• If brief delay is needed for corticosteroid administration or transfer, nifedipine or indomethacin may be considered, though specific data before 26 weeks are lacking 1.

Mode of Delivery

• Routine cesarean delivery is not recommended for preterm labor alone at 35 weeks 1, 7.
• Mode of delivery should be based on standard obstetric indications, not gestational age alone 1.

Key Clinical Pitfalls to Avoid

• Do not rely on oral antepartum antibiotic treatment for GBS colonization—it is ineffective and does not prevent neonatal disease 3.
• Do not withhold GBS prophylaxis in women with positive GBS cultures regardless of whether they received antepartum treatment 3.
• Do not aggressively attempt to prolong pregnancy at 35 weeks with tocolytics when neonatal outcomes are favorable 4, 5.
• Ensure evaluation for temperature ≥38.0°C and rupture of membranes ≥18 hours, as these are risk factors requiring specific management 2.