A Cochrane review [Abstract] 1 included 4 studies with a total of 1 646 subjects. 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). There was no statistically significant differences in the risk of eclampsia (capsules: n=1242; 3 trials; lozenges: n=944; one trial), pre-eclampsia (capsules n=1197; 2 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.
Comment: The quality of evidence is downgraded by limitations in study quality (inadequate or unclear allocation concealment, more than 20% loss to follow up) and by inconsistency (heterogeneity in interventions and outcomes). The included trials were conducted between 1960 to 1983, and thus did not include important neonatal outcomes which have only recently been associated with vitamin B6, such as cardiovascular malformations and orofacial clefts.
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