Table 2.
Associations of folic acid supplementation and dietary folate intake with the risk of small for gestational age (SGA) among women (n 8758) and their children enrolled in the 2010–2012 Gansu Provincial Maternity and Child Care Hospital birth cohort, Lanzhou, China
| Folic acid/folate intake duration | AGA (n 7974) | SGA (n 784) | OR | 95 % CI | OR* | 95 % CI |
|---|---|---|---|---|---|---|
| Folic acid supplement | ||||||
| Non-users | 1762 | 252 | 1·00 | Ref. | 1·00 | Ref. |
| Users | 6212 | 532 | 0·60 | 0·51, 0·70 | 0·72 | 0·60, 0·86 |
| ≤12 weeks | 3239 | 321 | 0·69 | 0·58, 0·83 | 0·79 | 0·66, 0·96 |
| >12 weeks | 2973 | 211 | 0·70 | 0·64, 0·78 | 0·78 | 0·70, 0·87 |
| P trend | <0·001 | <0·001 | ||||
| Per 2-week increase | 0·943 | 0·928, 0·959 | 0·962 | 0·945, 0·979 | ||
| Before conception and during pregnancy | 2344 | 155 | 0·46 | 0·37, 0·57 | 0·58 | 0·46, 0·75 |
| <24 weeks | 1101 | 78 | 0·50 | 0·38, 0·65 | 0·61 | 0·45, 0·81 |
| ≥24 weeks | 1243 | 77 | 0·66 | 0·58, 0·75 | 0·77 | 0·66, 0·90 |
| P trend | <0·001 | <0·001 | ||||
| Per 2-week increase | 0·937 | 0·919, 0·954 | 0·955 | 0·935, 0·976 | ||
| Before conception only | 294 | 28 | 0·67 | 0·44, 1·01 | 0·84 | 0·54, 1·29 |
| ≤8 weeks | 123 | 12 | 0·68 | 0·37, 1·25 | 0·76 | 0·41, 1·41 |
| >8 weeks | 171 | 16 | 0·81 | 0·62, 1·05 | 0·95 | 0·72, 1·26 |
| P trend | 0·061 | 0·471 | ||||
| Per 2-week increase | 0·936 | 0·870, 1·008 | 0·975 | 0·904, 1·052 | ||
| During pregnancy only | 3574 | 349 | 0·68 | 0·58, 0·81 | 0·78 | 0·65, 0·94 |
| ≤8 weeks | 1415 | 164 | 0·81 | 0·66, 1·00 | 0·85 | 0·68, 1·06 |
| >8 weeks | 2159 | 185 | 0·77 | 0·70, 0·86 | 0·85 | 0·76, 0·95 |
| P trend | <0·001 | 0·002 | ||||
| Per 2-week increase | 0·948 | 0·925, 0·970 | 0·966 | 0·942, 0·991 | ||
| Dietary folate intake (µg/d) | ||||||
| Before pregnancy | ||||||
| Q1 < 115·63 | 1963 | 232 | 1·00 | Ref. | 1·00 | Ref. |
| Q2 = 115·63–157·42 | 2002 | 157 | 0·66 | 0·54, 0·82 | 0·78 | 0·62, 1·00 |
| Q3 = 157·42–218·91 | 1959 | 206 | 0·94 | 0·85, 1·04 | 1·04 | 0·93, 1·16 |
| Q4 ≥ 218·91 | 2050 | 189 | 0·92 | 0·86, 1·00 | 1·02 | 0·93, 1·12 |
| P trend | 0·124 | 0·311 | ||||
| Per 10-μg increase | 0·996 | 0·982, 1·010 | 1·014 | 0·997, 1·031 | ||
| During pregnancy | ||||||
| Q1 < 149·47 | 1971 | 240 | 1·00 | Ref. | 1·00 | Ref. |
| Q2 = 149·47–197·56 | 1967 | 185 | 0·77 | 0·63, 0·95 | 0·92 | 0·73, 1·15 |
| Q3 = 197·56–263·21 | 1988 | 166 | 0·83 | 0·75, 0·92 | 0·97 | 0·86, 1·10 |
| Q4 ≥ 263·21 | 2048 | 193 | 0·92 | 0·86, 0·98 | 1·06 | 0·96, 1·18 |
| P trend | 0·005 | 0·418 | ||||
| Per 10-μg increase | 0·985 | 0·971, 0·998 | 1·012 | 0·995, 1·030 | ||
AGA, appropriate for gestational age; Q, quartile; ref., reference category.
Multiplicative interaction on SGA: OR = 0·85 (95 % CI 0·71, 1·01), P = 0·062.
*
OR adjusted for maternal age, monthly income per capita, maternal education level, smoking, maternal employment, pre-pregnancy BMI, weight gain during pregnancy, pre-eclampsia, parity, caesarean section, height of child’s father, history of preterm birth, total energy intake, dietary folate intake or folic acid supplement.