Table 4.
Pre- and post-conception folic acid supplementation and risk of heart defects
| Folic acid supplementation | Pre-conception FA use | Post-conception FA use | ||||
|---|---|---|---|---|---|---|
| No. of malformations/infants | Adjusted odds ratio (95% CI)a | P value | No. of malformations/infants | Adjusted odds ratio (95% CI)a | P value | |
| Supplementation | ||||||
| No | 7/873 | 1.00 | 7/873 | 1.00 | ||
| Yes | 28/6808 | 0.68 (0.28–1.66) | 0.40 | 31/8598 | 0.45 (0.20–1.03) | 0.059 |
| Initiation | ||||||
| No supplementation | 7/873 | 1.00 | 7/873 | 1.00 | ||
| Earlier than 4 months before pregnancy | 3/559 | 0.99 (0.24–4.12) | 0.99 | |||
| Between 4 and 3 months before pregnancy | 7/1210 | 1.03 (0.34–3.14) | 0.96 | – | ||
| Between 3 and 2 months before pregnancy | 6/1466 | 0.67 (0.22–2.10) | 0.49 | – | ||
| Between 2 and 1 month before pregnancy | 2/1053 | 0.29 (0.06–1.43) | 0.13 | – | ||
| Within 1 month before pregnancy | 10/2520 | 0.60 (0.22–1.62) | 0.31 | – | ||
| The first month of pregnancy | – | 16/4389 | 0.45 (0.18–1.12) | 0.085 | ||
| The second month of pregnancy | – | 10/3302 | 0.37 (0.14–0.98) | 0.045 | ||
| The third month of pregnancy | – | 5/907 | 0.65 (0.20–2.06) | 0.46 | ||
| Duration | ||||||
| No supplementation | 7/873 | 1.00 | 7/873 | 1.00 | ||
| 1 month | – | 6/1966 | 0.36 (0.12–1.08) | 0.68 | ||
| 1.01–2 months | – | 15/4524 | 0.41 (0.17–1.03) | 0.057 | ||
| 2.01–3 months | 10/1928 | 0.79 (0.29–2.15) | 0.64 | 10/2108 | 0.59 (0.22–1.59) | 0.30 |
| 3.01–4 months | 1/1200 | 0.12 (0.02–1.02) | 0.052 | |||
| 4.01–5 months | 3/922 | 0.53 (0.13–2.11) | 0.36 | |||
| 5.01–6 months | 9/1939 | 0.77 (0.27–2.19) | 0.63 | |||
| > 6 months | 5/819 | 1.18 (0.34–4.10) | 0.79 | |||
aAdjusted for region, maternal age, ethnicity, parity, conception mode, education level, family income, history of adverse pregnancy outcomes, medicine exposure, and early pregnancy conditions