Abstract P034: The Association Of Breastfeeding With Lower Blood Pressure Is Stronger In Children Born Vaginally Compared To Cesarean Section
Authors: Han Yipin , Zhao Jianbo H , Zhang Mingyu , Liu Tiange , Hong Xiumei , Wang Xiaobin , Mueller Noel T 
Published: April 2022

Introduction:
A recent study of mother-child pairs in Canada (Miliku et al., JAHA 2021) found that ever (vs. never) breastfeeding was associated with lower blood pressure (BP) in early childhood. The authors posited the effect is modulated by the microbiome. However, they did not examine if the breastfeeding effect is stronger in vaginally-delivered infants, whom host more bacterial species (e.g.,
Bifidobacteria
) that bioconvert human milk oligosaccharides into BP-lowering butyrate. Given their population was majority White, it is unknown if breastfeeding lowers BP in non-White populations.

Hypothesis:
Introduction to breast milk in infancy lowers BP in childhood, particularly among vaginally delivered infants, in a racially diverse population.

Methods:
We used data from the Boston Birth Cohort. We assessed breastfeeding status during the postnatal follow up at <2 years of age. Ever breastfeeding was defined as exclusively breastfed or a mix of breastfed and bottle-fed. We obtained repeated clinical measures of childhood systolic BP (SBP) across 0-17 years of age. We calculated age-, sex-, and height- specific child BP percentiles according to the 2017 American Academy of Pediatrics Clinical Practice Guidelines. We used linear regression with GEE with a link function and AR-1 correlation to examine the association of ever breastfeeding with child SBP. We controlled for maternal age, education, smoking, parity, pre-pregnancy BMI, hypertension, and child low birthweight, preterm birth, age, and sex. We assessed effect modification by race and delivery mode.

Results:
Our analytic sample comprised 19,597 BP measurements from 2,077 children, who were 52% male, 66% black, and had a mean age of 8 years. Among our sample, 33% were born preterm, 59% were vaginally delivered, and 74% were ever breastfed. Ever (vs. never) breastfeeding was associated with 1.74 percentile (95% CI: -3.66, 0.19; p=0.08) lower SBP. In children who were delivered vaginally, ever breastfeeding was associated with 2.63 percentile (95% CI: -5.12, -0.14; p=0.04) lower SBP. In contrast, among children delivered by Cesarean section, SBP percentile was not significantly reduced (95% CI: -3.45, 2.59; p=0.78) among ever breastfed. Moreover, ever breastfeeding was more strongly associated with lower BP among participants who self-identified as non-Black (3.40 percentile lower SBP; 95% CI: -6.30, -0.49; p=0.02) vs. Black (0.98 percentile lower SBP; 95% CI: -3.42, 1.45; p=0.43).

Conclusion:
In our racially diverse cohort, ever vs. never breastfeeding was associated with lower BP among children who were delivered vaginally, but not among those delivered by Cesarean section. The protective association of ever breastfeeding on child BP was also weaker in those born to mothers who self-identified as Black, highlighting the need for more research on the effects of breastfeeding on cardiometabolic health in racial minority groups.