Abstract P165: Effects of Lactation on Postpartum Blood Pressure among Women with Gestational Hypertension and Preeclampsia

Introduction: Lactation is associated with improved maternal blood pressure (BP) in later life and in the postpartum period among normotensive women. However, little is known about whether lactation is also cardio-protective in women with pregnancy-related hypertensive disorders. This study aimed to characterize the relationship between lactation and postpartum BP in women who remained normotensive during pregnancy compared to those who developed preeclampsia or gestational hypertension. Hypothesis: Lactation will be associated with lower postpartum BP, particularly in women with hypertensive disorders of pregnancy. Methods: Data were obtained from a cohort of normotensive women who participated in the Prenatal Exposures & Preeclampsia Prevention study (n=651; 65% African American; 83% overweight or obese prior to pregnancy). Women were enrolled during pregnancy and attended a postpartum visit where data on lactation and BP were collected following a standardized protocol. Analysis of variance (ANOVA) was used to assess the relationship between lactation and postpartum BP in women who remained normotensive during pregnancy, developed gestational hypertension (2 or more BP measurements >140/90), or developed preeclampsia (gestational hypertension plus proteinuria). Further analyses adjusted for age, race, smoking, prepregnancy weight, and time since delivery. Results: A total of 439 women attended the postpartum study visit (mean time since birth 8.5 months); 50 (11%) developed gestational hypertension, and 38 (9%) preeclampsia. Lactation was reported by 246 (56%) with 84 (19%) reporting lactation for ≥ 6 months. Women who lactated were older, wealthier, and more likely to plan to lactate compared to those who did not lactate. There was no association between lactation duration and postpartum systolic BP for women who remained normotensive during pregnancy (never lactated: 111.0 mmHg vs. lactated ≥ 6 months: 112.9 mmHg, p=0.83) nor among women who developed preeclampsia (never lactated: 121.3 mmHg vs. lactated ≥ 6 months: 128.3 mmHg, p=0.35). However, greater lactation duration was associated with lower systolic BP among women who developed gestational hypertension (never lactated: 127.8 mmHg vs. lactated ≥ 6 months: 109.4 mmHg, p=0.04). This relationship remained significant after adjusting for covariates. Similarly, lactation was associated with lower postpartum diastolic BP only for women with a history of gestational hypertension. Conclusions: Lactation appears to lower postpartum BP among women who develop gestational hypertension, but do not develop preeclampsia. Future work should investigate the mechanisms driving the relationship between lactation and postpartum BP in gestational hypertension.