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Vaginal birth possible in 50% of women with low-lying placenta



About half of women with an asymptomatic low-lying placenta in the third trimester and an internal os distance of 11-20 mm can have a vaginal birth after 35 weeks without any higher risk of severe complications than if they had undergone elective cesarean delivery, a new study indicates.

The retrospective analysis of 128,233 births between 2007 and 2012 at six hospitals in France showed that of the 171 women (0.13%) with low-lying placenta, 70 underwent a trial of labor, and 101 had an elective cesarean delivery. The vaginal delivery rate was 50.0% in the group of 38 women with an internal os distance of 11-20 mm, and 18.5% among 27 women with an internal os distance of 1-10 mm.

Similar rates of severe postpartum hemorrhage (PPH) were observed whether the patient opted for a trial of labor or for elective cesarean delivery (22.9% vs. 23.0%), regardless of maternal age, prepregnancy body mass index, nulliparity, and previous cesarean delivery. Rates of severe maternal and neonatal morbidity were 2.9% vs. 2.0%, and 12.9% vs. 9.9%, respectively, both nonsignificantly different, the study showed.

These findings confirm results from an earlier study and could reduce the incidence of unnecessary cesarean deliveries in women with low-lying placenta, said researchers led by Loïc Sentilhes, MD, PhD, of the department of obstetrics and gynecology at Bordeaux (France) University Hospital Center.

“Our results support a policy of offering a trial of labor to women with low-lying placenta at or after 35 weeks of gestation and a distance of 11-20 mm between the placental edge and the internal os on ultrasonography,” they wrote in Obstetrics & Gynecology.

Although an internal os distance of 1-10 mm did not increase the incidence of severe PPH or other severe maternal morbidity, 80% of these patients went on to have an emergency cesarean section. For this reason, the high risk of emergency cesarean should be discussed during shared decision-making, the study authors said.

Avoiding unnecessary cesarean deliveries is crucial to limiting the occurrence of low-lying placenta, placenta previa, vasa previa, and placenta accreta spectrum in subsequent pregnancies, Dr. Sentilhes told this news organization. “We hope that our results will help caregivers to objectively advise their patients with low-lying placenta regarding the choice of their mode of delivery.”

“This is further evidence to reassure clinicians that managing such patients with labor is a reasonable approach,” said Aaron B. Caughey, MD, MPH, PhD, professor and chair of the department of obstetrics and gynecology at Oregon Health & Science University, Portland. He was not involved in the study.

Many obstetricians have practiced this for decades, noted Dr. Caughey, associate dean for women’s health research and policy at Oregon Health. “We manage these patients expectantly with a plan for a trial of labor.”

“I am absolutely in agreement,” said Sarah L. Pachtman, MD, an obstetrician-gynecologist at Long Island Jewish Medical Center in New York, who is an independent expert. Dr. Pachtman noted that since she works at a hospital equipped for emergency cesarean deliveries, “I can get a baby out in 5 minutes if necessary.”

Dr. Pachtman’s practice consists of “a very large population of women who strongly desire vaginal delivery.

“It’s a better recovery for them, avoids the risks of abdominal surgery, gives them quicker skin-to-skin contact with their newborn and they can start breastfeeding sooner,” she said in an interview. “And the risk of bleeding is actually lower compared to elective cesarean delivery.”

Deciding on the mode of delivery should be based on patient preference and physician comfort, shared decision-making, and where the patient delivers, Dr. Pachtman said. “If the placental edge is between 1 mm and 10 mm or abutting the internal os, I explain to the patient that there is a risk of bleeding even before labor starts, and they would most likely want to choose an elective cesarean delivery.”

Although low-lying placenta can be associated with significant maternal and neonatal morbidity and mortality, particularly when diagnosed at delivery, universal cervical length screening during routine anatomic ultrasound is identifying the presence of low-lying placenta much earlier in pregnancy.

“We’re identifying it more, following it more, and reporting it more,” Dr. Pachtman said. And in the vast majority of patients, she emphasized, the 28-week follow-up transvaginal ultrasound shows that the low-lying placenta has resolved.

Dr. Sentilhes reported a relationship with Ferring Laboratories. No other study authors disclosed having conflicts of interest. Dr. Caughey and Dr. Pachtman reported having no conflicts of interest.

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