Women who breastfeed, especially those with prior gestational diabetes mellitus (GDM), appear to have greater protection against long-term atherosclerotic cardiovascular disease (ASCVD), suggest the results of a study presented at SMFM 2025.

“These findings suggest the beneficial impact of breastfeeding for long-term maternal cardiovascular health, especially among those with GDM,” said lead author Dr Christine P Field from The Ohio State University, Columbus, OH, US.

To determine whether breastfeeding helped lower the estimated risk of long-term ASCVD, as assessed 10 to 14 years after delivery, Field and her team performed a secondary analysis of the prospective Hyperglycemia and Adverse Pregnancy Outcome Follow-up Study (HAPO FUS).

Any breastfeeding served as the main exposure. The primary outcome was the estimated ASCVD risk, defined as a composite of fatal and nonfatal coronary heart disease and stroke, over the next 10- and 30-year time periods measured separately.

Field and colleagues then measured the ASCVD risk, calculated as a continuous percentage, 10 to 14 years after delivery using the Framingham Risk Score. They also used multivariable linear regression models, with adjustments for baseline covariates: field centre, age, BMI, height, smoking and alcohol use, parity, and time from delivery to ASCVD risk assessment.

In addition, the research team determined whether the association of breastfeeding with ASCVD varied by GDM status (effect modification).

Overall, 4,540 women were included in the analysis. Their median age at baseline was 30.6 years. More than three in four participants reported breastfeeding in the multisite international cohort, which showed a similar GDM status (79.5 percent vs 81.0 percent). [SMFM 2025, abstract 99]

At a median of 11.6 years after delivery, women who had breastfed were shown to have a much lower estimated ASCVD risk over the next 10 years (adjusted β, ?0.13, 95 percent confidence interval [CI], ?0.25 to ?0.02) or over the subsequent 30 years (adjusted β, ?0.36, 95 percent CI, ?0.66 to ?0.05).

Field stressed that the protective effect of breastfeeding against ASCVD significantly varied by GDM status (p<0.01 for interaction). Of note, breastfeeding provided over fivefold greater protection for women with prior GDM (10-year estimated ASCVD risk: adjusted β, ?0.52, 95 percent CI, ?0.98 to ?0.05; p=0.004; 30-year risk: adjusted β, ?1.33, 95 percent CI, ?2.53 to ?0.14; p=0.003).

Inflammation

Inflammation tends to influence breastfeeding in women, with higher rates being associated with lower prenatal versus postpartum inflammatory markers, suggests another study presented at SMFM 2025.

In adjusted models, lower circulating inflammatory markers during pregnancy correlated with greater breastfeeding intensity across week 6, month 3, and month 6. On the other hand, the postpartum inflammatory composite correlated with breastfeeding intensity at point of blood draw (6 weeks). [SMFM 2025, abstract 548]

“Inflammation in pregnancy may influence lactogenesis and breastfeeding initiation, differentiating breastfeeding outcomes in the postpartum period,” said lead author Dr Margaret S. Butler from the Center of Excellence in Maternal and Child Health, Chicago, IL, US.