Longer Labor Duration During Second-Trimester Medication Abortions Raises Risk of Adverse Maternal Outcomes: Study

Medication abortion, a method increasingly used for terminating pregnancies in the second trimester, involves administering drugs to induce labor and expulsion of the fetus. While generally considered safe, the study found that prolonged labor durations—defined as the time from medication administration to delivery—are linked with heightened complications.

"For each additional hour of labor duration, the frequency of maternal morbidity increased by 0.47%," Ashish Premkumar, Pritzker School of Medicine, University of Chicago, Chicago, IL, and colleagues reported.

The study was conducted to evaluate the relationship between the duration of labor during second-trimester medication abortion and adverse outcomes.

For this purpose, the researchers conducted a retrospective cohort study involving individuals with a singleton pregnancy undergoing second-trimester medication abortion at four different centers. The study excluded cases with advanced cervical dilation, rupture of membranes, or preterm labor. The primary focus was on labor duration, specifically the hours from receiving misoprostol to fetal expulsion.

The primary outcome measured was composite morbidity, which included uterine rupture, the need for blood transfusion, clinical chorioamnionitis, admission to the intensive care unit, or readmission. To analyze the data, the team used both bivariate and multivariate negative binomial methods. Additionally, a post hoc subgroup analysis was conducted to evaluate the risk of the primary outcome relative to gestational age. The researchers also performed tests of homogeneity to account for factors such as history of uterine scarring and parity.

The following were the key findings of the study:

• Six hundred eighty-one individuals were included. The median duration of labor was 11 hours.
• 19.2% experienced the primary outcome.
• When the duration of labor was evaluated continuously, a longer duration of labor was associated with an increased frequency of morbidity.
• When the duration of labor was evaluated categorically, those experiencing the highest quartile of duration (ie, 17 hours or more) had a statistically higher risk for experiencing morbidity compared with individuals in all other quartiles (adjusted relative risk 1.99).
• When the focus was on components of the composite outcome, clinical chorioamnionitis was significantly different between those experiencing a longer duration and those experiencing a shorter duration of labor (26.2% versus 10.6%).
• On subgroup analysis, gestational age was not associated with the risk of composite morbidity.
• Tests of homogeneity demonstrated no significant difference in the risk for morbidity among individuals with a history of uterine scarring or based on parity.

"The duration of labor was found to be independently linked to an increased risk of adverse maternal outcomes during second-trimester medication abortion, particularly clinical chorioamnionitis," the researchers concluded.

Reference:

Premkumar, Ashish MD, PhD; Manthena, Vanya MPH; Wascher, Jocelyn MD; Wanyonyi, Eryn K. MD; Johnson, Camille MD; Vuppaladhadiam, Lahari BA; Chor, Julie MD, MPH; Plunkett, Beth A. MD, MPH; Ryan, Isa MD; Mbah, Olivert MPH; Lee, Jungeun MS; Barker, Emily MD; Laursen, Laura MD, MS; McCloskey, Leanne R. MD, MPH; York, Sloane L. MD, MPH. Duration of Induction of Labor for Second-Trimester Medication Abortion and Adverse Outcomes. Obstetrics & Gynecology 144(3):p 367-376, September 2024. | DOI: 10.1097/AOG.0000000000005663