Bone Abstracts

We have previously observed sex-specific effects of maternal calcium supplementation on offspring childhood growth, in a rural Gambian population with habitually low calcium intake (~300 mg daily).^1,2 There was no effect on maternal blood pressure, the primary outcome of the original trial.³ In this study, we aim to investigate effects on offspring blood pressure (BP) in the same cohort. We recruited children (205 female, 182 male) born following a randomised, placebo-controlled trial of calcium supplementation during pregnancy (1500 mg daily from gestational week 20 until delivery, ISRCTN96502494). Offspring BP was measured using the Omron 705IT monitor, at mean(S.D.) age 13.8(1.2) years. Outcomes were resting sitting systolic and diastolic BP (SBP, DBP). Linear regression was used to determine the effects of maternal calcium supplementation on an intention-to-treat basis, separately among boys and girls, first adjusted for age only and then further adjusted for height and BMI. Boys and girls were then pooled to test for a sex-supplement interaction. Mean(S.D.) SBP/DBP was 108(11)/62(9) mmHg among girls and 103(11)/59(10) mmHg among boys. Girls whose mothers had received the calcium supplement during pregnancy had lower BP than those whose mothers received placebo (mean(95%CI) difference in SBP: −4.4(−7.1,−1.7) mmHg; DBP: −2.5(−4.9,−0.1) mmHg). These differences were partly attenuated when height and BMI were included in the models (SBP: −2.8(−5.3,−0.3) mmHg; DBP: −1.6(−3.9,+0.7) mmHg). No significant differences in BP were observed among boys (SBP: +1.3(−1.7,+4.4) mmHg; DBP: +0.7(−2.2,+3.5) mmHg). In the pooled analysis, the sex-supplement interaction was significant for SBP (+5.7(+1.6,+9.7) mmHg) but not for DBP (+3.2(−0.5,+6.9) mmHg). Maternal calcium supplementation was associated with reduced BP among girls during adolescence, but not among boys. A previous analysis in the same cohort at mean age 7 years showed no result of maternal calcium supplementation on offspring BP,⁴ suggesting that these differences may develop with age. Further follow-up will be required to determine whether the difference persists into adulthood and to investigate potential long-term effects on cardiometabolic health.

Funding: UK Medical Research Council and Department for International Development under the MRC/DFID Concordat (programmes U105960371 and U123261351); Sackler Institute for Nutrition Science, New York Academy of Sciences.

Disclosure: The authors declared no competing interests.

References:
(1) Ward et al. JBMR 2015 30 (S1) OP1096.
(2) Ward et al. OI 2016 27 (S1) P585.
(3) Goldberg et al. AJCN 2013 98 972–82.
(4) Hawkesworth et al. AJCN 2010 92 741–7.