Figure 1.

(a–c) Harvest plots of the evidence for associations of smoking with folate, vitamin B12, and homocysteine levels. One study did not report information on significance and is therefore not presented in the harvest plot (Sram et al., 2005). * indicates associations were determined at different time points in pregnancy. If there were discrepancies in the significance between the time points, the plot represents the significance of the measurement of the latest time point. † indicates levels of folate were measured in different blood components (e.g., maternal plasma, serum, or red blood cells). If there were discrepancies in the significance between the components, the plot represents the significance of the measurement most comparable with the measurements of the other studies (Table 2). The study of Gadowsky et al. measured levels of folate in maternal plasma and red blood cells; results of maternal RBC are shown. The study of Larroque et al. measure levels of folate in maternal serum and maternal RBC; results of maternal serum are shown. ‡ indicates significance was determined using different statistical tests. If there were discrepancies in the significance between tests, only the significance of the regression analysis is shown