Lactation and Maternal Subclinical Atherosclerosis Among Women With and Without a History of Hypertensive Disorders of Pregnancy

Background: We evaluated subclinical cardiovascular disease in relation to lactation history among women with normotensive pregnancies and women with hypertensive pregnancies, a distinction not previously examined. Materials and Methods: The POUCHmoms study included 678 women from a pregnancy cohort who were followed 7-15 years after delivery. We measured blood pressure, lipid levels, carotid intima-media thickness (CIMT), and lactation duration for each live birth (LB) at follow-up. We categorized lactation as never, <6 months/LB, or ≥6 months/LB. We analyzed associations between lactation and cardiometabolic risk factors and CIMT by using analysis of variance and multivariable linear regression (adjusted for age, race, socioeconomic status, smoking, time from last pregnancy, and total parity), which produced adjusted least square mean differences (LSMdiff) between groups. Results: In the normotensive pregnancies group with women who never lactated as the referent ( n  = 157): Women with some lactation but <6 months/LB ( n  = 284) had higher high density lipoprotein (HDL) (LSMdiff = +4.47 mg/dL, p  = 0.013), lower triglycerides (LSMdiff = -38.1 mg/dL, p  = 0.02), and thinner mean CIMT (LSMdiff = -0.03 mm, p  = 0.005); women who lactated for ≥6 months/LB ( n  = 133) also had higher HDL (LSMdiff = +7.59 mg/dL, p  < 0.001), lower triglycerides (LSMdiff = -41.6 mg/dL, p  = 0.01), and thinner mean CIMT (LSMdiff = -0.03 mm, p  = 0.003). After further adjustment for body mass index, associations between lactation and HDL, triglycerides, and mean CIMT persisted. These associations were not detected in women with prior hypertensive pregnancies. Conclusions: Women with a history of normotensive pregnancies and lactation for any duration had a more favorable cardiometabolic profile and were at decreased risk of subclinical atherosclerosis compared with those who never lactated.