Bone Abstracts

Objective: We have observed sex-specific effects of pregnancy calcium carbonate supplementation in 8–12 year old Gambian children, indicating slower growth after infancy in girls born to calcium-supplemented mothers but faster in boys.^1,2 IGF-1 is a key driver of growth and is responsive to calcium supplementation.³ The aim of this study was to determine whether the pregnancy supplement had resulted in sex-specific effects on mid-childhood IGF1 of the offspring.

Methods: Archived data from a study of the offspring of Gambian mothers who participated in ISRCTN96502494 were used. These women were randomised to 1500 mgCa/d as calcium carbonate (Ca) or placebo (P) from 20 weeks pregnancy to delivery. Of the 546 children born, 389 were followed-up and 290 had plasma IGF-1 and IGF-BP3 assayed by Immulite 1000 (n/group: female(F)-Ca=77, F-P=73, Male(M)-Ca=64, M-P=76). The IGF-1 distribution was normalised using square root transformation. Maternal supplement effects were considered using regression with sexes separated and then together to test for a sex*supplement interaction (P-values given). IGF-1 summaries are presented as geometric mean (−1gSE, +1gSE); group differences as sympercents±SE (difference/mean).

Results: The children were 7.5 (S.D.1.2) years, there were no significant sex or supplement group differences in age, weight or height. Mean IGF-1 concentrations (ng/ml) were F-Ca=99.5(4.8,5.1), F-P=118.9(6.4,6.8), M-Ca=78.1(4.3,4.5), M-P=67.7(3.4,3.6). Girls had higher IGF-1 than boys in both supplement groups (P<0.001). IGF-1 was lower in F-Ca than F-P (−18±7%, P=0.01) but higher in M-Ca than M-P (+14±8%, P=0.05); sex*supplement P=0.001. IGF-BP3 differences were in similar direction but effect sizes were smaller. Although attenuated after IGF-BP3 adjustment (F-Ca v F-P=−15±7%, P=0.02; M-Ca v M-P=+8±7%, P=0.2), sex*supplement remained significant (P=0.008).

Conclusion: Calcium carbonate supplementation of pregnant rural Gambian mothers resulted in lower IGF-1 in girls and higher IGF-1 in boys during mid-childhood before effects on growth were apparent. These results are consistent with the observed effects of the maternal supplement on the growth trajectories of the offspring.

Funded by European Union Sixth Framework (FOOD-CT-2005-007036), MRC programmes U105960371, U123261351, MC-A760-5QX00 and DfID under the MRC/DfID Concordat.

Disclosure: The authors declared no competing interests.

References:
1,2 Ward, Jarjou, Prentice JBMR 2015, S1; Osteoporos Int 2016, S1.

3. Ginty, Prentice et al in Nutritional Aspects of Osteoporosis, Elsevier 2004.