What are the guidelines for inducing labor at 38 weeks gestation?

Induction of Labor at 38 Weeks Gestation

Routine elective induction at 38 weeks is not recommended for low-risk pregnancies; induction should be reserved for medical or obstetric indications at this gestational age, with elective induction delayed until 39 weeks 0 days or later. 1, 2

Timing Guidelines for Elective Induction

Elective induction should never be performed before 39 weeks 0 days gestation due to increased neonatal respiratory morbidity and other adverse outcomes. 1, 3, 4 The FDA labeling for oxytocin explicitly states that available data are inadequate to define benefit-to-risk considerations for elective induction, emphasizing that oxytocin is indicated for medical rather than elective induction. 2

For Low-Risk Nulliparous Women

• Elective induction at 39 weeks 0 days is recommended as it reduces cesarean delivery rates from 22.2% to 18.6% (number needed to treat = 28) and decreases hypertensive disorders from 14.1% to 9.1%. 1
• This recommendation is supported by high-quality randomized trial evidence specifically in nulliparous women. 1, 5

For Multiparous Women

• Evidence supporting elective induction at 39 weeks does not extend to multiparous women, as all high-quality trials were conducted exclusively in nulliparous populations. 3
• Expectant management until spontaneous labor or development of medical indication may be more appropriate given the lack of specific evidence. 3

Medical Indications for Induction at 38 Weeks

Induction at 38 weeks is appropriate when continuing pregnancy poses greater risks than delivery. 1, 2 Specific indications include:

Hypertensive Disorders

• Gestational hypertension or mild preeclampsia at 37 weeks or later warrants induction to improve maternal outcomes. 1

Fetal Growth Restriction

• For FGR with normal umbilical artery Doppler and estimated fetal weight between 3rd-10th percentile, deliver at 38-39 weeks. 6
• For FGR with abnormal Doppler (elevated resistance but preserved end-diastolic flow), deliver by 37-38 weeks depending on severity. 6
• The U.S. guidelines recommend delivery at 38+0 to 39+6 weeks for FGR with no additional abnormal parameters. 6
• New Zealand guidelines recommend delivery by 38 weeks if umbilical artery Doppler >95th percentile, middle cerebral artery <5th percentile, or cerebroplacental ratio <5th percentile. 6

Other Medical Indications at 38 Weeks

• Maternal diabetes with poor glycemic control 1, 2
• Rh disease requiring early delivery 2
• Premature rupture of membranes at term 2

Critical Contraindications at 38 Weeks

Suspected fetal macrosomia is NOT an indication for induction at any gestational age, as it doubles cesarean risk without reducing shoulder dystocia or neonatal morbidity. 1

Previous cesarean delivery with misoprostol use carries a 13% uterine rupture risk and is absolutely contraindicated. 1

Common Pitfalls to Avoid

• Do not perform elective induction before 39 weeks 0 days even if the cervix is favorable or the patient requests earlier delivery. 1, 3
• Do not extrapolate nulliparous data to multiparous women when counseling about elective induction benefits. 3
• Ensure clear documentation of medical indication if inducing at 38 weeks, as this is not considered elective timing. 2
• Assess cervical favorability with Bishop score before selecting induction method; unfavorable cervix (Bishop <5) requires cervical ripening agents first. 3, 7

Cervical Ripening Methods at 38 Weeks

For unfavorable cervix at 38 weeks with medical indication:

• Single-balloon Foley catheter (60-80 mL) for 12 hours combined with either oral misoprostol (25 μg every 2-4 hours or 50 μg every 4-6 hours) or oxytocin infusion is recommended. 8
• Dinoprostone gel is FDA-approved for cervical ripening at or near term with medical or obstetrical need. 7
• Avoid misoprostol in patients with previous uterine surgery and dinoprostone in those with active cardiovascular disease. 1