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Table 3 The subgroup analyses of studies concerning the association between maternal FA supplementation and the risk of CHD 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 18 0.821 (0.720, 0.936)  < 0.001 92.7
Design
 Case–control 12 0.801 (0.648, 0.991)  < 0.001 94.7
 Cohort or RCT 6 0.936 (0.837, 1.047) 0.003 72.2
Geographic region
 Europe or Australia 7 0.955 (0.840, 1.086) 0.001 72.1
 China 4 0.580 (0.433, 0.776)  < 0.001 89.6
 America 7 0.921 (0.874, 0.971) 0.358 9.3
Publication period
 Before 2010 5 0.927 (0.737, 0.936) 0.253 25.2
 2010 or after 13 0.800 (0.690, 0.928)  < 0.001 94.7
Quality assessment
 High quality studies (scores ≥ 7) 11 0.803 (0.641, 1.007)  < 0.001 95.5
 Low quality studies (scores < 7) 7 0.898 (0.832, 0.969) 0.120 40.6
Confounding Factors
 Age 14 0.821 (0.720, 0.936)  < 0.001 94.2
 Maternal smoking 5 0.751 (0.562, 1.005)  < 0.001 94.9
 Maternal alcohol 2 0.801 (0.677, 0.948) 0.512 0
 Maternal BMI 5 0.829 (0.676, 1.016)  < 0.001 83
 Fetal sex 2 0.806 (0.654, 0.992) 0.471 0
 Family history 2 0.726 (0.324, 1.623)  < 0.001 93.8
  1. FA folic acid, CHD congenital heart disease