Table 2.

Post-conception folic acid supplementation and risk of congenital malformations

Variants of folic acid supplementation	Risk of congenital malformations
	No. of malformations	No. of infants	Prevalence,% (95% CI)	Adjusted odds ratio (95% CI)a	P value
Supplementation
No	21	887	2.37 (1.37–3.37)	1.00
Yes	128	8695	1.47 (1.22–1.73)	0.64 (0.40–1.03)	0.063
Initiation
No supplement	21	887	2.37 (1.37–3.37)	1.00
The first month	57	4430	1.29 (0.95–1.62)	0.55 (0.33–0.91)	0.02
The second month	51	3343	1.53 (1.11–1.94)	0.64 (0.38–1.07)	0.086
The third month	20	922	2.17 (1.23–3.11)	0.91 (0.49–1.70)	0.77
Duration
No supplement	21	887	2.37 (1.37–3.37)	1.00
1 month	33	1993	1.66 (1.10–2.22)	0.68 (0.39–1.19)	0.17
1.01 months ~	63	4572	1.38 (1.04–1.72)	0.59 (0.36–0.98)	0.041
2.01 months ~	32	2130	1.50 (0.99–2.02)	0.66 (0.38–1.17)	0.15

^aAdjusted for region, maternal age, ethnicity, parity, conception mode, education level, family income, history of adverse pregnancy outcomes, medicine exposure, and early pregnancy conditions