Pyridoxine (vitamin B6) supplementation in pregnancy

Background Vitamin B6 plays vital roles in numerous metabolic processes in the human body, such as nervous system development and functioning. It has been associated with some benefits in non-randomised studies, such as higher Apgar scores, higher birthweights, and reduced incidence of pre-eclampsia and preterm birth. Recent studies also suggest a protection against certain congenital malformations. Objectives To evaluate the clinical effects of vitamin B6 supplementation during pregnancy and/or labour. Search strategy We searched the Cochrane Pregnancy and Childbirth Group Trials Register (30 December 2005). Selection criteria We included randomised controlled trials comparing vitamin B6 administration in pregnancy and/or labour with: placebos, no supplementations, or supplements not containing vitamin B6. Data collection and analysis Two authors independently extracted data and assessed trials for methodological quality. We used relative risk and weighted mean difference with 95% confidence intervals. Main results Five trials (1646 women) were included. Four trials used blinding. One had adequate method of randomisation and allocation concealment; four did not report this. Three trials had large losses to follow up. Vitamin B6 as oral capsules or lozenges resulted in decreased risk of dental decay in pregnant women (capsules: relative risk (RR) 0.84; 95% confidence interval (CI) 0.71 to 0.98; one trial, n = 371; lozenges: RR 0.68; 95% CI 0.56 to 0.83; one trial, n = 342). A small trial showed reduced mean birthweights with vitamin B6 supplementation (weighted mean difference -0.23 kg; 95% CI -0.42 to -0.04; n = 33; one trial). We did not find any statistically significant differences in the risk of eclampsia (capsules: n = 1242; three trials; lozenges: n = 944; one trial), pre-eclampsia (capsules n = 1197; two trials; lozenges: n = 944; one trial) or low Apgar scores at one minute (oral pyridoxine: n = 45; one trial), between supplemented and non-supplemented groups. No differences were found in Apgar scores at one or five minutes, or breastmilk production between controls and women receiving oral (n = 24; one trial) or intramuscular (n = 24; one trial) loading doses of pyridoxine at labour. Authors' conclusions There were few trials, reporting few clinical outcomes and mostly with unclear trial methodology and inadequate follow up. There is not enough evidence to detect clinical benefits of vitamin B6 supplementation in pregnancy and/or labour other than one trial suggesting protection against dental decay. Future trials assessing this and other outcomes such as orofacial clefts, cardiovascular malformations, neurological development, preterm birth, pre-eclampsia and adverse events are required.