Reduction in Bone Loss from 5 to 20 Weeks Postpartum in Adolescents Supplemented with Calcium Plus Vitamin D during Pregnancy Is Not Sustained at 1 Year Postpartum: Follow-up Study of a Randomized Controlled Trial

Abstract

Background: Calcium plus vitamin D supplementation of pregnant Brazilian adolescents with habitually low calcium intake (∼600 mg/d) reduced bone loss during the first 20 wk postpartum.

Objective: We investigated maternal bone mass changes during the first year postpartum as a follow-up of the clinical trial.

Methods: Pregnant adolescents (14-19 y) received calcium (600 mg/d) plus cholecalciferol (200 IU/d) supplementation (n = 30) or placebo (n = 26) from 26 wk of gestation until parturition. Bone area and bone mineral content and bone mineral density (BMD) at total body, lumbar spine, and hip (total and femoral neck) were assessed by DXA at 3 time points postpartum (5 wk, 20 wk, and 56 wk). Intervention group, time postpartum, and group × time interaction effects were tested by repeated-measures mixed-effects models adjusting for calcium intake, return of menses, breastfeeding practices, and body weight.

Results: Time (P < 0.05) but not group affected several absolute bone measurements. There was a group × time interaction for femoral neck BMD (P = 0.045). Mean ± SE values (g/cm2) at 5 wk, 20 wk, and 56 wk were, respectively, 1.025 ± 0.026, 0.980 ± 0.026, and 1.022 ± 0.027 for the placebo group and 1.057 ± 0.025, 1.030 ± 0.024, and 1.055 ± 0.025 for the supplemented group. An interaction also was observed for percentage change in femoral neck BMD relative to 5 wk (P = 0.049), with a more pronounced decrease in the placebo group (-4.58 ± 0.42%) than in the supplemented group (-3.15% ± 0.42%) at 20 wk (P = 0.019), and no difference between groups at 56 wk (-0.44% ± 0.71% in the placebo and -0.76% ± 0.62% in the supplemented group; P = 0.65).

Conclusions: Calcium plus vitamin D supplementation of the adolescent mothers reduces the magnitude of bone loss at the femoral neck from 5 to 20 wk postpartum without an effect on bone changes after 1 y postpartum, indicating that there is no sustained effect of the supplement tested.

Keywords: adolescence; adolescent mothers; bone health; bone mineral density; intervention; lactation.