Vitamin B12 and Increased Maternal Vitamin B12 Concentration

low birthweight (RR 1.50, 95% CI 0.93 to 2.43; 2 trials, 344 women; low-certainty evidence)

there may be little to no difference for maternal anaemia by intervention group, but the evidence is very uncertain (70.9% versus 65.0%; risk ratio (RR) 1.08, 95% CI 0.93 to 1.26; 2 trials, 284 women; very low-certainty evidence).

the evidence is uncertain about the effect on adverse pregnancy outcomes, including preterm birth (RR 0.97, 95% CI 0.55 to 1.74; 2 trials, 340 women; low-certainty evidence)

Two trials reported data on spontaneous abortion (or miscarriage); however, the trials did not report quantitative data for meta-analysis and there was no clear definition of spontaneous abortion in the study reports.