LAS VEGAS (FRONTLINE MEDICAL NEWS) – Delivery at 38 weeks’ gestation is linked with improved perinatal survival among singleton infants born to morbidly obese mothers in a retrospective review of more than 2 million U.S. births.

“If reasonable, consider delivery at 38 weeks in morbidly obese mothers” delivering singleton pregnancies, Ruofan Yao, MD , said at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.

Despite the known excess fetal morbidity and mortality associated with pregnancies in obese mothers, “we see a lack of recommendations for antenatal testing and early delivery,” said Dr. Yao, a maternal-fetal medicine physician at the University of Maryland, Baltimore.

When mothers have diabetes, hypertension, or cholestasis, they receive frequent prenatal testing and fetal growth measurements, and delivery is typically at 37, 38, or 39 weeks. “This is what we also need to think about for morbidly obese mothers,” Dr. Yao said.

“Because of increased fetal growth in morbidly obese mothers there is probably earlier placental insufficiency,” he said in an interview.

The upshot is that, once a morbidly obese mother reaches 38 weeks’ gestation, induced labor should be considered, according to Dr. Yao. Induction could start immediately if the mother’s cervix is ripe, or clinicians could first take steps to hasten cervical ripening.

Induction can be especially slow in morbidly obese women, who are generally less sensitive to oxytocin and can require multiple induction strategies.

While Dr. Yao considered the evidence he reported persuasive enough to recommend this strategy, he cautioned that, ideally, the benefits of an early-delivery approach should be confirmed in a prospective, randomized trial.

The study used delivery records maintained by the state of Texas for 2006-2011. Of the more than 2.4 million births recorded during the period, Dr. Yao excluded multiple deliveries, births at less than 34 weeks’ or more than 42 weeks’ gestation, deliveries from underweight mothers (less than 18.5 kg/m2), and fetal anomalies. This left 2,181,530 births, of which 52% were by normal weight mothers (18.5-24 kg/m2), 26% by overweight mothers (25-29 kg/m2), 18% by obese mothers (30-39 kg/m2), and 4% by morbidly obese mothers (40 kg/m2 or greater). The women averaged 27 years old, 4% had preeclampsia, and 4% had pregestational diabetes.

The researchers then calculated perinatal mortality rates relative to gestational age at birth for women in each body mass index stratum. The calculations showed no significant impact of gestational age among late-term deliveries by normal weight, overweight, and obese mothers, but, among morbidly obese mothers, early deliveries made a difference and were significantly linked with reduced perinatal mortality.

Every 400 deliveries, approximately, induced at 38 weeks among morbidly obese mothers resulted in one less perinatal death, Dr. Yao reported . This relationship held even when the researchers excluded mothers with preeclampsia or pregestational diabetes (about 8% of the study group).

Dr. Yao had no disclosures.

On Twitter @mitchelzoler


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