MINERAL AND VITAMIN INTERVENTIONS FOR AT-RISK POPULATIONS
Location: Obesity and Metabolism Research Unit
Title: Interventions with vitamins B6, B12 and C in pregnancy
Submitted to: PAEDIATRIC AND PERINATAL EPIDEMIOLOGY
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2011
Publication Date: July 1, 2012
Citation: Dror, D.K., Allen, L.H. 2012. Interventions with vitamins B6, B12 and C in pregnancy. PAEDIATRIC AND PERINATAL EPIDEMIOLOGY. 26 (Suppl. 1), 55-74.
Interpretive Summary: A critical review of evidence from intervention trials with vitamins B6, B12 and C during pregnancy suggests that while risks of supplementation are minimal, benefits are not clearly delineated. Supplementation with vitamin B6 during pregnancy may reduce symptoms of nausea and vomiting, improve dental health,treat some cases of maternal anaemia, and reduce the incidence of some congenital abnormalities, though additional research is needed to confirm these results. In meta-analysis vitamin B6 supplementation had a significant positive effect on birthweight, though total sample size was small and one trial included supplementation with doxylamine. Vitamin C deficiency has been implicated in pre-eclampsia and PROM; however, interventions to improve status during pregnancy have not systematically reduced the incidence of these complications. In meta-analysis, there was a significant treatment effect of vitamin C and E in increasing the risk of pregnancy-related hypertension; other effects of vitamin C or C and E intervention on maternal and neonatal outcomes, including preterm birth, birthweight, and perinatal morbidity and mortality, were not significant. Data on child health outcomes following maternal supplementation with vitamins B6 and C are not available. Overall, existing evidence does not justify vitamin B6 or C supplementation during pregnancy, though well-designed RCTs investigating potential benefits of vitamin B6 supplementation are warranted. Deficiency of vitamin B12 is highly prevalent in women of reproductive age, especially amongst populations with limited intake of animal source foods. To determine whether improvement of maternal status reduces the incidence of NTDs in the offspring, increases breast milk vitamin
B12 content during lactation, and improves infant vitamin B12 status, RCTs with vitamin B12 supplementation during the periconceptual period and pregnancy are necessary.
The water-soluble vitamins B6, B12 and C play important roles in maternal health as well as fetal development and physiology during gestation. This systematic review evaluates the risks and benefits of interventions with vitamins B6, B12 and C during pregnancy on maternal, neonatal and child health and nutrition outcomes. Relevant publications were identified by searching PubMed, Popline and Web of Science databases. Meta-analyses were conducted for outcomes where results from at least three controlled trials were available. Potential benefits of vitamin B6 supplementation were reduction in nausea and vomiting, improvement in dental health, and treatment of some cases of anaemia. In meta-analysis based on three small studies, vitamin B6 supplementation had a significant positive effect on birthweight (d = 217 g [95% confidence interval (CI) 130, 304]). Interventions with vitamin C alone or combined with vitamin E did not systematically reduce the incidence of pre-eclampsia, premature rupture of membranes, or other adverse pregnancy outcomes. In meta-analyses, vitamins C and E increased the risk of pregnancy-related hypertension (relative risk 1.10 [95% CI 1.02, 1.19]). Effects of vitamin B6 or C intervention on other neonatal outcomes, including preterm birth, low birthweight, and perinatal morbidity and mortality, were not significant. Data on child health outcomes were lacking. Despite the prevalence of vitamin B12 deficiency amongst populations with limited intake of animal source foods, no intervention trials have evaluated vitamin B12 supplementation before or during pregnancy. In conclusion, existing evidence does not justify vitamin C supplementation during pregnancy. Additional studies are needed to confirm positive effects of vitamin B6 supplementation on infant birthweight and other outcomes. While vitamin B12 supplementation may reduce the incidence of neural tube defects in the offspring based on theoretical considerations, research is needed to support this hypothesis.