When a near-term fetus is estimated to be large for gestational age, induction of labor prior to the estimated due date may reduce delivery-related morbidity, according to new data.

Macrosomia increases the risk of shoulder dystocia—a delivery complication in which the fetal shoulders become impacted behind the maternal pubic symphysis following delivery of the head, preventing spontaneous delivery of the body.

To assess whether early-term induction might mitigate this risk, investigators enrolled 2,893 pregnant individuals whose fetuses measured above the 90th percentile for gestational age on ultrasound.

Participants were randomized to either standard expectant management or induction of labor between 38 weeks 0 days and 38 weeks 4 days’ gestation. Earlier delivery was hypothesized to lower birth weight and reduce complications.

In the full cohort, shoulder dystocia rates were similar between groups. However, a post hoc analysis excluding those who delivered before 38 weeks demonstrated a shoulder dystocia rate of 2.3% in the induction group versus 3.7% in the expectant management group.

On average, delivery occurred 8 days earlier in the induction group, and neonatal birth weight was reduced by approximately 213 grams (8 ounces).

After adjusting for relevant maternal and obstetric factors, the adjusted odds ratio for shoulder dystocia was 0.62 in the induction group compared with standard care among those who remained pregnant beyond 38 weeks—a 38% risk reduction.

Elective induction was also associated with a decreased likelihood of cesarean delivery and fewer maternal complications, the investigators reported.

In an accompanying editorial, the authors note, “The Big Baby Trial joins an accumulating body of literature... indicating that induction of labor either does not alter or might reduce the risk for needing cesarean delivery” when fetal macrosomia is suspected.

Source: The Lancet