Study: Low-Lying Placenta Ups Complications in C-Sections

SAN FRANCISCO — Patients with a low-lying placenta who underwent cesarean deliveries were at higher risk for multiple complications even if they did not have placenta previa, according to data presented at the American College of Obstetricians and Gynecologists (ACOG) 2024 Annual Meeting.

Rates of preterm delivery, postpartum hemorrhage, placenta accreta, and need for hysterectomy and transfusion were all significantly higher in patients with low-lying placenta than in patients without, Jacob Thomas, MD, of Advocate Aurora Health in Chicago, Illinois, and Ascension Illinois St. Alexius Medical Center in Hoffman Estates, reported at the meeting.

A low-lying placenta is defined as a placental edge less than 20 mm from the internal os but not covering it. Most studies looking at low-lying placentas, however, group them with placenta previa, making it difficult to know if there are differences in risk of adverse outcomes for those who don't have placenta previa.

"These are not necessarily shocking findings, but it shows that even low-lying placentas have significant morbidity in and of themselves, not just when they're lumped with placenta previas," Dr Thomas said in an interview. "This means, if you're doing a C-section for a low-lying placenta, you probably want to treat it a lot like you would treat a placenta previa. You may have blood ready, whether or not you're going to give it, and you're going to be more prepared for those complications."

Noting that approximately 30% of patients with low-lying placenta had preterm deliveries, Dr Thomas added that these patients might need to be counseled differently as well. The researchers did not have data on how preterm the deliveries were — many could have been 35-37 weeks, for example — but "how you prepare those patients is different," he said.

Breanna Bolivar, MD, MPH, an Ob/Gyn hospitalist at MAHEC Ob/Gyn Specialists in Asheville, North Carolina, said the findings confirm her experience in practice.

"Low-lying placentas are treated very similarly to placenta previas and the results seem similar to patients that have placenta previas," Dr Bolivar said in an interview. "In my practice, I treat patients with low-lying placenta the same as I do with placenta previa. I have the same risk factors in mind, and I prepare in the same way."

The researchers conducted a retrospective analysis of all patients who underwent a cesarean delivery in the National Inpatient Sample from 2017 to 2019 through the Healthcare Cost and Utilization Project from the Agency for Healthcare Research and Quality. After excluding patients with placenta previa, the researchers compared outcomes among patients with ICD-10 codes for low-lying placenta to those of patients without low-lying placenta. The researchers specifically looked at preterm delivery, hemorrhage, hysterectomy, placenta accreta spectrum (PAS), sepsis, shock, disseminated intravascular coagulation, and blood transfusion.

Among 700,635 patients with cesarean deliveries in the database, 0.4% had low-lying placenta. These patients were more likely to be older, to be anemic, and to deliver at a large or urban teaching hospital. They were less likely to have public insurance or a previous cesarean.

After controlling for confounders that differed between the two populations, the researchers found a higher likelihood of all adverse maternal outcomes studied in patients with low-lying placenta (P < .05). These patients had three times greater risk for preterm delivery (adjusted odds ratio [aOR], 3.07; 95% CI, 2.81-3.35) and nearly three times greater risk for shock (aOR, 2.55; 95% CI, 1.44-4.52), and transfusion (aOR, 2.56; 95% CI, 2.14-3.06).

Compared to those without low-lying placenta, risk for patients with low-lying placenta was even higher for hemorrhage (aOR, 8.87; 95% CI, 8.10-9.73), hysterectomy (aOR, 9.42; 95% CI, 7.11-12.47), and PAS (aOR, 13.41; 95% CI, 10.34-17.39).

Within the group with low-lying placenta, older patients were modestly, but significantly, more likely to have hemorrhage, hysterectomy, and PAS (aOR, 1.06 for all). The risk was more elevated and significant in patients with tobacco use for hemorrhage (aOR, 1.43), hysterectomy (aOR, 1.40), and PAS (aOR, 1.40). Patients with anemia were also significantly more likely to experience PAS (aOR, 1.34).

"Interestingly, in this population, prior cesarean was not associated with increased rates of hemorrhage or hysterectomy," the researchers reported. The findings can also "help guide research in terms of questions for the future," Dr Thomas said, such as looking at complication rates for vaginal deliveries in people with low-lying placenta.

No external funding was noted, and the authors all had no disclosures. Dr Bolivar had no disclosures.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.