Table 1.
General characteristics and incidence of congenital malformations between women with and without folic acid supplementation
| General characteristics and congenital malformations | Folic acid supplementation | |||
|---|---|---|---|---|
| Yes (N = 15,848) | No (N = 887) | Total (N = 16,735) | P value | |
| Region | 0.32 | |||
| East | 7900 (49.8) | 442 (49.8) | 8345 | |
| West | 4084 (25.8) | 210 (23.7) | 4301 | |
| North | 2974 (18.8) | 176 (19.8) | 3150 | |
| Central | 890 (5.6) | 59 (6.7) | 949 | |
| Han ethnicity | 15,119 (95.4) | 845 (95.3) | 15,964 (95.4) | 0.67 |
| Education level (years) | < 0.001 | |||
| < 9 | 1426 (9.0) | 137 (15.4) | 1563 (9.3) | |
| 10–12 | 2157 (13.6) | 157 (17.7) | 2314 (13.8) | |
| 13–15 | 4044 (25.5) | 241 (27.2) | 4285 (25.6) | |
| ≥ 16 | 8221 (51.9) | 352 (39.7) | 8573 (51.2) | |
| Family income (RMB Yuan per person per month)a | 0.043 | |||
| < 3000 | 537 (3.4) | 35 (3.9) | 572 (3.4) | |
| 3000–5000 | 4936 (31.1) | 308 (34.7) | 5244 (31.3) | |
| 5001–8000 | 5149 (32.5) | 284 (32.0) | 5433 (32.5) | |
| > 8000 | 4770 (30.1) | 230 (25.9) | 5000 (29.9) | |
| History of adverse pregnant outcomesb | 2884 (18.2) | 129 (14.5) | 3013 (18.0) | 0.006 |
| Early-pregnant conditionsc | 6169 (38.9) | 308 (34.7) | 6477 (38.7) | 0.012 |
| Natural conception | 14,649 (92.4) | 862 (97.2) | 15,511 (92.7) | < 0.001 |
| Periconceptional medicine exposure | 4221 (26.6) | 194 (21.9) | 4415 (26.4) | 0.002 |
| Nulliparous women | 10,812 (68.2) | 441 (49.7) | 11,253 (67.2) | < 0.001 |
| Maternal age (years) | 0.001 | |||
| < 25 | 1527 (9.6) | 109 (12.3) | 1636 (9.8) | |
| 25–34 | 12,679 (80.0) | 663 (74.7) | 13,342 (79.7) | |
| ≥ 35 | 1642 (10.4) | 115 (13.0) | 1757 (10.5) | |
| Congenital malformations | ||||
| Total, no. (%) | 252 (1.6) | 21 (2.4) | 273 (1.6) | 0.075 |
| Heart defects, no. (per 1000 infants) | 60 (3.8) | 7 (7.9) | 67 (4.0) | 0.089 |
| Neural tube defects, no. (per 10,000 infants) | 11 (6.9) | 1 (11.3) | 12 (7.2) | 0.47 |
aInformation of family income was not available for 486 women
bAdverse pregnancy outcomes refer to abortion, ectopic pregnancy, infertility, induced labour, congenital malformations, or preterm birth in previous pregnancies
cEarly pregnancy conditions mean influenza/cold, a fever ≥ 38℃, skin rash, vaginal bleeding, thyroid dysfunction, gestational hyperglycemia/diabetes, gastrointestinal diseases, gynaecological inflammation or diseases