Is there an association between lateral uterine localization of the placenta and pregnancy outcomes?

Purpose: To evaluate the association between lateral placentation and adverse perinatal outcomes, including rates of small for gestational age (SGA) neonates, hypertensive (HTN) disorders, and preterm delivery, as well as postpartum hemorrhage and retained placenta. Methods: This retrospective cohort study included all women with singleton pregnancies who underwent a trial of labor after reaching 24 weeks of gestation, at a single tertiary medical center, over a period of 6 years. The study group included women with lateral placentation. Controls were women with anterior, posterior, or fundal placentation. Power analysis indicated that 882 women in each group would be sufficient to detect an increased rate of the primary outcomes: preterm delivery, hypertensive disorders or SGA in the lateral placenta group. Secondary outcomes were Apgar score, cord pH and retained placenta. Results: Overall, 1,817 (7.6%) women had lateral placenta and 21,991 (92.4%) anterior, posterior, or fundal placentation. No significant differences were observed between groups in the rates of hypertensive disorders, SGA or preterm birth. Lateral placentation was associated with a longer third stage of labor (11.1 ± 8.6 min vs. 10.4 ± 7.2 min, p = 0.001) and higher rate of retained placenta (5.7% vs. 4.2%, p = 0.002). Multivariate regression found that lateral placentation was independently associated with longer third stage of labor. Conclusion: Lateral placentation was not associated with increased rates of hypertensive disorders, preterm birth or SGA infants. It was linked to a longer third stage of labor but without a significant impact on maternal or perinatal complications.