Table 4.
Associations of folic acid supplementation and dietary folate intake with the risk of nulliparous small for gestational age (SGA) and multiparous 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 | Nulliparous SGA | Multiparous SGA | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Controls (n 5826) |
Cases (n 535) |
OR | 95 % CI | OR* | 95 % CI | Controls (n 2148) |
Cases (n 249) |
OR | 95 % CI | OR* | 95 % CI | |
| Folic acid supplement | ||||||||||||
| Non-users | 982 | 138 | 1·00 | Ref. | 1·00 | Ref. | 780 | 114 | 1·00 | Ref. | 1·00 | Ref. |
| Users | 4844 | 397 | 0·58 | 0·48, 0·72 | 0·67 | 0·54, 0·84 | 1368 | 135 | 0·68 | 0·52, 0·88 | 0·80 | 0·61, 1·06 |
| ≤12 weeks | 2379 | 224 | 0·67 | 0·54, 0·84 | 0·73 | 0·58, 0·93 | 860 | 97 | 0·77 | 0·58, 1·03 | 0·90 | 0·67, 1·22 |
| >12 weeks | 2465 | 173 | 0·71 | 0·63, 0·80 | 0·79 | 0·69, 0·91 | 508 | 38 | 0·72 | 0·59, 0·87 | 0·77 | 0·63, 0·95 |
| P trend | <0·001 | <0·001 | <0·001 | 0·022 | ||||||||
| Per 2-week increase | 0·949 | 0·932, 0·967 | 0·965 | 0·946, 0·985 | 0·933 | 0·902, 0·966 | 0·951 | 0·917, 0·985 | ||||
| Before conception and during pregnancy | 1971 | 132 | 0·48 | 0·37, 0·61 | 0·62 | 0·46, 0·83 | 373 | 23 | 0·42 | 0·27, 0·67 | 0·52 | 0·32, 0·85 |
| <24 weeks | 889 | 64 | 0·51 | 0·35, 0·70 | 0·64 | 0·45, 0·91 | 212 | 14 | 0·62 | 0·44, 0·88 | 0·70 | 0·48, 1·01 |
| ≥24 weeks | 1082 | 68 | 0·67 | 0·58, 0·78 | 0·79 | 0·66, 0·94 | 161 | 9 | 0·45 | 0·25, 0·80 | 0·53 | 0·29, 0·97 |
| P trend | <0·001 | 0·002 | <0·001 | 0·010 | ||||||||
| Per 2-week increase | 0·941 | 0·921, 0·962 | 0·960 | 0·937, 0·984 | 0·920 | 0·879, 0·964 | 0·938 | 0·893, 0·986 | ||||
| Before conception only | 224 | 21 | 0·67 | 0·41, 1·08 | 0·85 | 0·51, 1·41 | 70 | 7 | 0·68 | 0·31, 1·53 | 0·83 | 0·36, 1·88 |
| During pregnancy only | 2649 | 244 | 0·66 | 0·53, 0·82 | 0·71 | 0·56, 0·90 | 925 | 105 | 0·78 | 0·59, 1·03 | 0·90 | 0·67, 1·21 |
| ≤8 weeks | 983 | 110 | 0·80 | 0·61, 1·04 | 0·78 | 0·59, 1·03 | 432 | 54 | 0·86 | 0·61, 1·21 | 0·97 | 0·68, 1·39 |
| >8 weeks | 1666 | 134 | 0·76 | 0·67, 0·86 | 0·83 | 0·72, 0·95 | 493 | 51 | 0·71 | 0·50, 1·01 | 0·79 | 0·54, 1·14 |
| P trend | <0·001 | 0·002 | 0·051 | 0·265 | ||||||||
| Per 2-week increase | 0·954 | 0·925, 0·982 | 0·969 | 0·941, 0·998 | 0·943 | 0·902, 0·996 | 0·958 | 0·915, 1·004 | ||||
| Dietary folate intake (µg/d) | ||||||||||||
| Before pregnancy | ||||||||||||
| Q1 < 115·63 | 1399 | 147 | 1·00 | Ref. | 1·00 | Ref. | 564 | 85 | 1·00 | Ref. | 1·00 | Ref. |
| Q2 = 115·63–157·42 | 1523 | 122 | 0·76 | 0·59, 0·99 | 0·90 | 0·68, 1·18 | 479 | 35 | 0·49 | 0·32, 0·73 | 0·56 | 0·36, 0·90 |
| Q3 = 157·42–218·91 | 1450 | 139 | 0·96 | 0·85, 1·08 | 1·07 | 0·94, 1·23 | 509 | 67 | 0·94 | 0·79, 1·11 | 0·96 | 0·79, 1·17 |
| Q4 ≥ 218·91 | 1454 | 127 | 0·94 | 0·87, 1·02 | 1·02 | 0·91, 1·14 | 596 | 62 | 0·88 | 0·79, 0·99 | 1·02 | 0·87, 1·19 |
| P trend | 0·338 | 0·440 | 0·182 | 0·713 | ||||||||
| Per 10-μg increase | 1·004 | 0·988, 1·021 | 1·022 | 1·004, 1·041 | 0·979 | 0·956, 1·003 | 1·001 | 0·973, 1·031 | ||||
| During pregnancy | ||||||||||||
| Q1 < 149·47 | 1294 | 156 | 1·00 | Ref. | 1·00 | Ref. | 677 | 84 | 1·00 | Ref. | 1·00 | Ref. |
| Q2 = 149·47–197·56 | 1484 | 127 | 0·71 | 0·56, 0·91 | 0·85 | 0·65, 1·12 | 483 | 58 | 0·97 | 0·68, 1·38 | 1·08 | 0·73, 1·60 |
| Q3 = 197·56–263·21 | 1560 | 113 | 0·78 | 0·68, 0·88 | 0·90 | 0·78, 1·05 | 428 | 53 | 0·99 | 0·83, 1·20 | 1·18 | 0·95, 1·47 |
| Q4 ≥ 263·21 | 1488 | 139 | 0·92 | 0·85, 0·99 | 1·06 | 0·93, 1·20 | 560 | 54 | 0·92 | 0·82, 1·04 | 1·11 | 0·92, 1·34 |
| P trend | 0·019 | 0·794 | 0·223 | 0·373 | ||||||||
| Per 10-μg increase | 0·992 | 0·975, 1·009 | 1·019 | 0·998, 1·040 | 0·975 | 0·952, 0·999 | 0·999 | 0·969, 1·030 | ||||
Q, quartile; ref., reference category.
Multiplicative interaction on nulliparous SGA: OR = 0·88 (95 % CI 0·72, 1·08), P = 0·228.
Multiplicative interaction on multiparous-SGA: OR = 0·79 (95 % CI 0·56, 1·11), P = 0·174.
OR adjusted for maternal age, monthly income per capita, education level, smoking, employment, pre-pregnancy BMI, weight gain during pregnancy, pre-eclampsia, caesarean section, height of child’s father, history of preterm, total energy intake, dietary folate intake or folic acid supplement.