RESUMO
BACKGROUND: Pregnancy and lactation in adolescents with low calcium intake may impair fetal growth and infant bone mass. OBJECTIVE: We investigated the effects of calcium plus vitamin D supplementation during pregnancy in Brazilian adolescent mothers consuming low calcium diets (â¼600 mg/d) on fetal biometry and infant bone mass, and the relation between infant and maternal bone mass during early lactation. METHODS: Infants of mothers who received calcium (600 mg/d) plus cholecalciferol (200 IU/d) supplementation (n = 30) or placebo (n = 26) from 26 wk of gestation until parturition were studied. Fetal biometric measurements at 23 and 36 wk of gestation were obtained from medical records. Infant anthropometric and total body bone measurements [bone mineral content (BMC), bone area (BA), and bone mineral density (BMD)] at 5 wk postpartum were assessed by dual-energy X-ray absorptiometry. Maternal BMD z scores for total body, lumbar spine, total hip, and femoral neck at 5 wk postpartum were obtained. Group comparisons were adjusted for significant covariates. RESULTS: Maternal mean serum 25-hydroxyvitamin D was 59 nmol/L at baseline in both groups. No differences in fetal measurements at 36 wk of gestation were observed between the groups, except for body weight and its increment from 23 to 36 wk, which were higher in the supplemented group (6.8%, P = 0.014 and 10.5%, P = 0.07, respectively). Infant BMC (61.1 ± 21.7 g), BA (167 ± 79 cm(2)), and BMD (0.385 ± 0.069 g/cm(2)) did not significantly differ between the groups. In the placebo group, infant BMC and BA were negatively correlated with maternal BMD z scores for total body (r = -0.40 and r = -0.47; P < 0.05) and hip (r = -0.41 and r = -0.46; P < 0.05). In contrast, no correlations were observed in the supplemented group. CONCLUSIONS: Calcium and vitamin D supplementation of the adolescents studied resulted in higher fetal body weight at 36 wk of gestation and had no effect on infant bone mass at 5 wk postpartum. Because correlations between maternal and infant bone mass were evident only in the placebo group, infant bone mass appeared to be more dependent on maternal skeletal mass when calcium intake was low. This trial was registered at clinicaltrials.gov as NCT01732328.
Assuntos
Densidade Óssea/efeitos dos fármacos , Cálcio da Dieta/administração & dosagem , Suplementos Nutricionais , Terceiro Trimestre da Gravidez , Vitamina D/administração & dosagem , Absorciometria de Fóton , Adolescente , Brasil , Aleitamento Materno , Feminino , Colo do Fêmur/efeitos dos fármacos , Colo do Fêmur/metabolismo , Desenvolvimento Fetal , Humanos , Lactente , Lactação , Vértebras Lombares/efeitos dos fármacos , Vértebras Lombares/metabolismo , Gravidez , Método Simples-CegoRESUMO
BACKGROUND: Pregnancy and lactation in adolescents with habitually low calcium intake may adversely affect maternal bone mass. OBJECTIVE: We investigated the effect of calcium plus vitamin D supplementation during pregnancy on bone mass during lactation in Brazilian adolescent mothers with low-calcium diets (â¼600 mg/d). DESIGN: Pregnant adolescents (14-19 y) randomly received daily calcium (600 mg) plus vitamin D3 (200 IU) (n = 30) or a placebo (n = 26) from 26 wk of pregnancy (baseline) until parturition. The bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) at the total body, lumbar spine, and hip (total and femoral neck) were evaluated by using dual-energy X-ray absorptiometry at 5 and 20 wk postpartum. Serum hormones and 25-hydroxyvitamin D [25(OH)D] were measured. Group comparisons were adjusted for significant covariates. RESULTS: The mean serum 25(OH)D concentration was 59 nmol/L at baseline. In comparison with the placebo, 25(OH)D tended to be 14-15 nmol/L higher postpartum in the supplemented group (P = 0.08). Total body and hip BMC and BMD decreased over time (P ≤ 0.005) in both groups with a group × time interaction at the femoral neck (P < 0.04). Supplemented mothers had higher lumbar spine BA (6.7%; P = 0.002) and lumbar spine BMC (7.9%, P = 0.08) than did mothers who consumed the placebo at 5 wk postpartum. At 20 wk postpartum, differences between groups were more evident, with higher lumbar spine BMC (13.9%), lumbar spine BA (6.2%), and lumbar spine BMD (10.6%) in the supplemented group (P ≤ 0.008). CONCLUSIONS: Calcium plus vitamin D supplementation during pregnancy of adolescents with low calcium intake results in higher lumbar spine bone mass and a reduced rate of femoral neck bone loss during lactation. Additional studies are required to determine whether bone effects are temporary or long-lasting. This trial was registered at clinicaltrials.gov as NCT01732328.