Placental lesions and fetal growth in pregnancy after metabolic bariatric surgery- a matched cohort study.

BACKGROUND

Metabolic bariatric surgery (MBS) improves long-term metabolic health but has been associated with altered fetal growth patterns. The placental mechanisms underlying these outcomes remain incompletely characterized.

OBJECTIVES

To compare placental histopathology and perinatal outcomes in pregnancies following MBS versus matched controls.

SETTING

University hospital.

METHODS

This retrospective matched cohort study included 306 term, singleton deliveries, comprising 153 pregnancies following MBS and 153 controls matched for maternal age, prepregnancy body mass index (BMI) and gestational age at delivery. Maternal demographics, pregnancy characteristics, delivery and neonatal outcomes, and placental histopathology were analyzed. Placental lesions were classified according to the standardized Amsterdam criteria, including maternal vascular malperfusion (MVM), fetal vascular malperfusion (FVM), and inflammatory lesions. Multivariate logistic regression was performed to evaluate independent predictors of small for gestational age (SGA) neonates.

RESULTS

Maternal characteristics including demographics, rates of hypertensive disorders, diabetes mellitus, use of assisted reproductive technology, and smoking rates were comparable between the groups. In the post-MBS group birthweight was lower (3076±513 vs. 3308±427 g, P < .001), with a significantly higher rate of SGA (26.7% vs. 9.1%, P < .001) compared to the control group. Placental examination demonstrated higher rates of villous lesions of maternal malperfusion (54.2% vs. 41.8%, P = .030), and a higher composite rate of maternal malperfusion lesions (62.0% vs. 48.3%, P = .016) in the post-MBS group. In multivariate analysis, MBS (adjusted odds ratio [aOR] 3.41, 95% confidence interval [CI] 1.18-9.83), smoking (aOR 3.68, 95% CI 1.60-8.48), and composite maternal malperfusion lesions (aOR 2.92, 95% CI 1.26-6.77) were independently associated with the delivery of a SGA infant.

CONCLUSION

Pregnancies following MBS demonstrate increased placental maternal malperfusion lesions and a substantially higher risk of SGA neonates. These findings suggest that altered placental vascular development may contribute to fetal growth restriction in this population and highlight the importance of enhanced antenatal surveillance and placental-focused research in post-MBS pregnancies.