marginally significantP = 0.04
When analysed according to study design, a significant increase in maternal homocysteine was observed among prospective studies (RoM: 1.28, 95% CI: 1.14–1.44, P = 3.2 × 10 −5 ), with a marginally significant effect among retrospective studies (RoM = 1.07, 95% CI: 1.00–1.14, P = 0.04) ( Figure 1 ).