Table 1.
Characteristics of the study population.
| Variables | n=35,417 |
|---|---|
| Multiple deliveries (%) | 297 (0.8) |
| Singleton deliveries | 34,820 |
| Babies born | 35,417 |
| Boys (%) | 18,219 (51.9) |
| Girls (%) | 16,868 (48.0) |
| Maternal age in years, mean (SD) | 26.5 (5.3) |
| Maternal age distribution (%), n=35,084 | |
| <20 | 13.1 |
| 21–35 | 81.2 |
| >35 | 5.7 |
| Body mass index (BMI), mean (SD), n=34,325 | 23.41 (4.2) |
| BMI distribution, (%) | |
| <18.5 | 5.7 |
| 18.5–25.0 | 64.9 |
| >25.0 | 26.2 |
| Parity, n=35,101 | |
| 0 | 19,962 (56.9) |
| 1 | 12,425 (35.4) |
| ≥2 | 2,714 (7.7) |
| Previous spontaneous abortions (%), n=35,043 | |
| 0 | 30,934 (88.3) |
| ≥1 | 4,109 (11.7) |
| Education of mother in years (%), n=34,653 | |
| ≤11 | 13,046 (37.7) |
| >11 | 21,607 (62.3) |
| Paternal age, years, mean (SD) | 29.5 (6.0) |
| Gestational age, GA, in weeks, mean (SD) | 39.04 (2.3) |
| GA distribution, (%), n=33,694 | |
| 22–29 | 1.0 |
| 30–36 | 7.2 |
| 37–42 | 89.1 |
| >42 | 2.7 |
| Birth weight in g, mean (SD) | 3,340 (553) |
| Multivitamins taken before pregnancy (%) | 13.3 |
| Multivitamins taken during pregnancy (%) | 91.3 |
| Folic acid intake before pregnancy (%) | 8.5 |
| Folic acid intake during pregnancy (%) | 70.7 |
| Smoking before pregnancy (%) | 24.3 |
| Smoking during pregnancy (%) | 18.4 |
| Alcohol abuse during pregnancy (%) | 0.6 |
| Drugs abuse during pregnancy (%) | 0.5 |
SD, standard deviation.