Introduction:
High blood pressure (BP) is the leading modifiable risk factor of cardiovascular diseases. High maternal pre-pregnancy body mass index (BMI) may be one of earliest risk factors for high child BP, but evidence supporting this hypothesis is limited. Vitamin D was recently found to protect against elevated BP in childhood, yet no studies to our knowledge have examined if Vitamin D could be a modifiable target for mitigating the association of pre-pregnancy BMI and child BP.
Methods:
We analyzed longitudinal data of 719 mother-child pairs in the Boston Birth Cohort enrolled from 1998-2012 at the Boston Medical Center. We calculated child systolic BP (SBP) percentile according to a US reference and defined low Vitamin D as cord blood 25(OH)D concentration <11 ng/mL. We examined the change in child SBP percentile per 5-kg/m
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increment in pre-pregnancy BMI using linear regression models with GEE estimates. We adjusted for confounders (see Figure footnote) and assessed mediation by further adjusting for child BMI-z score.
Results:
Our analytic sample included 451 (63%) African American/Haitian mothers, 361 (50%) girls, and 304 (42%) children with low cord blood Vitamin D. A 5-kg/m
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increment in maternal pre-pregnancy BMI was associated with a 1.99 (95% CI: 1.08, 2.90) percentile increase in child SBP (during childhood [3-12 years]: 1.85, 95% CI: 0.97, 2.73; during adolescence [13-18 years]: 4.22, 95% CI: 1.19, 7.25). Cord blood Vitamin D status modified the associations (P-interaction = 0.023) (Figure, Panel A). Results were attenuated in the mediation analysis, but the interaction remained significant (Figure, Panel B).
Conclusion:
Higher maternal pre-pregnancy BMI is associated with higher offspring BP in childhood and adolescence, and this association is partially mediated by child weight. The inter-generational association disappeared if mother-newborn cord blood had high Vitamin D. Optimizing maternal Vitamin D status during pregnancy may help prevent the inter-generational cycle of cardiovascular risk.
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