Table 1 Characteristics of study participants
Characteristics | Naturally conceived newborns (n = 983) | ART-conceived newborns—fresh embryo (n = 764) | ART-conceived newborns—frozen embryo (n = 126) |
|---|---|---|---|
Maternal age at delivery, mean (SD) | 30 (4.6) | 33 (3.7) | 33.6 (3.5) |
Maternal parity, N (%) | Â | Â | Â |
 Nulliparous | 461 (46.9%) | 541 (70.8%) | 78 (61.9%) |
 Multiparous | 522 (53.1%) | 223 (29.2%) | 48 (38.1%) |
Maternal educational level, N (%) | Â | Â | Â |
 Less than high school | 71 (7.2%) | 43 (5.6%) | 3 (2.4%) |
 High school | 299 (30.4%) | 180 (23.6%) | 31 (24.6%) |
 Up to 4 years of college | 386 (39.3%) | 334 (43.7%) | 54 (42.9%) |
 More than 4 years of college | 225 (22.9%) | 204 (26.7%) | 38 (30.2%) |
 Missing | 2 (0.2%) | 3 (0.4%) | 0 (0%) |
Maternal pre-pregnancy BMI, mean (SD) | 24.3 (4.5) | 24.4 (4.2) | 23.8 (3.2) |
 Missing, N (%) | 14 (1.4%) | 15 (2%) | 1 (0.8%) |
Maternal smoking status during pregnancy, N (%) | Â | Â | Â |
 Never | 490 (49.8%) | 397 (52%) | 65 (51.6%) |
 Former | 253 (25.7%) | 279 (36.5%) | 47 (37.3%) |
 Quit before 18 gestational weeks | 132 (13.4%) | 47 (6.2%) | 10 (7.9%) |
 Continued after 18 gestational weeks | 104 (10.6%) | 37 (4.8%) | 4 (3.2%) |
 Missing | 4 (0.4%) | 4 (0.5%) | 0 (0%) |
Child sex, N (%) | Â | Â | Â |
 Male | 470 (47.8%) | 403 (52.7%) | 66 (52.4%) |
 Female | 513 (52.2%) | 361 (47.3%) | 60 (47.6%) |
Child birthweight (grams), mean (SD) | 3649.4 (525.6) | 3490.3 (531.4) | 3697.4 (577.2) |
 Missing, N (%) | 0 (0%) | 1 (0.1%) | 0 (0%) |
Maternal intake of folic acid supplement, N (%) | Â | Â | Â |
 Never or only before pregnancy | 156 (15.9%) | 49 (6.4%) | 9 (7.1%) |
 In pregnancy before week 18 | 395 (40.2%) | 84 (11%) | 19 (15.1%) |
 Before and up to week 18 of pregnancy | 432 (43.9%) | 631 (82.6%) | 98 (77.8%) |