Offering Trial of Labor for Low-lying placenta after 35 weeks of gestation appears safe, finds study

A new study revealed that the trial of labor can be offered to women with a low-lying placenta after 35 weeks of gestation and an internal os distance of 11–20 mm. This has neither increased postpartum hemorrhage nor maternal morbidity.

The study was published in the journal Obstetrics & Gynecology. 

The low-lying placenta is defined as the distance between the cervical os and the placenta. An internal os distance of 20 mm or less is associated with maternal and neonatal morbidity and mortality and also with an increased risk of antepartum, intrapartum, and postpartum hemorrhage. There is previous literature on perinatal outcomes in women with low-lying placenta but no data on antenatal symptoms. Hence researchers conducted a retrospective multicenter study of births to evaluate and compare maternal and neonatal morbidity of women with low-lying placenta by their planned mode of delivery and stratified by the internal os distance at the last predelivery ultrasound examination from 2007–2012. 

Pregnant women from six tertiary maternity hospitals in France participated in this study. Women with low-lying placenta having an internal os distance of 20 mm or less, who gave birth after 35 weeks of gestation were included. They were classified into the planned trial-of-labor or elective cesarean delivery groups. Severe postpartum hemorrhage (PPH) defined as blood loss exceeding 1,000 mL was the primary endpoint. Secondary outcomes were composite variables of severe maternal and neonatal morbidity. Multivariable logistic regression and propensity scores were used to compare outcomes by planned mode of delivery.  

RESULTS:

• Among 128,233 births during the study period, 171 (0.13%) women had low-lying placentas.
• Of these 70 (40.9%) were in the trial-of-labor group and 101 (59.1%) underwent elective cesarean delivery.
• 22.9% for the trial-of-labor group and 23.0% for the cesarean delivery group (P=.9) had severe PPH.
• Severe maternal and neonatal morbidity rates were likewise similar (2.9% vs 2.0% and 12.9% vs 9.9%, respectively).
• Trial-of-labor was not significantly associated with a higher rate of severe PPH after multivariable logistic regression and propensity score-weighted analysis.
• The vaginal delivery rate in the trial-of-labor group was 50.0% (19/38) in those with an internal os distance of 11–20 mm and 18.5% (5/27) in those with a distance of 1–10 mm.  

Thus, the researchers supported that trial of labor could be offered to women with the low-lying placenta after 35 weeks of gestation and an internal os distance of 11–20 mm as it did not increase the incidence of severe PPH or severe maternal morbidity. 

To read more, click here: 10.1097/AOG.0000000000004890 

Froeliger A, Madar H, Jeanneteau P, et al. Trial of Labor Compared With Elective Cesarean Delivery for Low-Lying Placenta [published online ahead of print, 2022 Aug 3]. Obstet Gynecol. 2022;10.1097/AOG.0000000000004890.