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Table 4 The subgroup analyses of studies regarding the association between maternal FA supplementation and the risk of ASD in offspring

From: Evaluation of the association between maternal folic acid supplementation and the risk of congenital heart disease: a systematic review and meta-analysis

Subgroup No. of studies OR (95%CI) P-value I2(%)
Summary pooled estimate 15 0.828 (0.716, 0.957)  < 0.001 86.5
Design
 Case–control 10 0.768 (0.646, 0.914)  < 0.001 87.7
 Cohort or RCT 5 1.010 (0.789, 1.291) 0.004 74
Geographic region
 Europe or Australia 7 0.892 (0.748, 1.065)  < 0.001 83.4
 China 4 0.564 (0.362, 0.879)  < 0.001 90.8
 America 4 1.008 (0.766, 1.327) 0.002 79.5
Publication period
 Before 2010 1 1.200 (0.800, 1.800)   
 2010 or after 14 0.811 (0.698, 0.941)  < 0.001 87.1
Quality assessment
 High quality studies (scores ≥ 7) 10 0.789 (0.652, 0.954)  < 0.001 90.0
 Low quality studies (scores < 7) 5 0.908 (0.730, 1.130) 0.009 70.2
Confounding Factors
 Age 13 0.795 (0.687, 0.919)  < 0.001 86.8
 Maternal smoking 4 0.748 (0.512, 1.094)  < 0.001 91.8
 Maternal alcohol 1 0.620 (0.469, 0.819)   
 Maternal BMI 5 0.704 (0.508, 0.975)  < 0.001 87
 Fetal sex 1 0.780 (0.617, 0.986)   
 Family history 2 0.664 (0.245, 1.801)  < 0.001 94.6
  1. FA folic acid, ASD atrial septal defects