Table 2.

Association between duration of maternal FA supplementation and occurrence of CHD or ASD

Folic acid intake	Authors (year)	Duration	CHD OR (95% Cl)	ASD OR (95% Cl)
Intake short-term before pregnancy	Li X et al. (2013) [31]	Before pregnancy ≤ 1 month	0.60 (0.31, 1.17)	0.53 (0.27, 1.05)
	Mao B et al. (2017) [34]	Before pregnancy ≤ 2 months
Intake short-term after pregnancy	Li X et al. (2013) [31]	During pregnancy < 1 month	0.79 (0.42, 1.47)	0.66 (0.41, 1.07)
	Mao B et al. (2017) [34]	During pregnancy ≤ 3 months
Intake long-term before pregnancy	Li X et al. (2013) [31]	Before pregnancy 1–3 months	0.39 (0.23, 0.68)	0.28 (0.13, 0.58)
	Mao B et al. (2017) [34]	Before pregnancy > 2 months
Intake long-term after pregnancy	Li X et al. (2013) [31]	During pregnancy > 1 months	0.60 (0.43, 0.83)	0.43 (0.26, 0.70)
	Mao B et al. (2017) [34]	During pregnancy ≥ 3 months

FA folic acid, CHD congenital heart disease, ASD atrial septal defects