Baseline characteristics responders and non-responders
| Individual characteristics | Responders (833) | Non-responders (2161) | P value |
| Median (IQR)/N (%) | Median (IQR)/N (%) | ||
| Maternal age (years) | 30 (27; 33) | 29 (26; 33) | <0.001 |
| <25 | 97 (11.7%) | 393 (18.3%) | |
| 25–29 | 265 (31.9%) | 700 (32.6%) | |
| 30–34 | 305 (36.7%) | 744 (34.6%) | |
| ≥35 | 163 (19.6%) | 312 (14.6%) | |
| Missing: 3 | Missing: 12 | ||
| Country of residence | 0.012 | ||
| United States | 728 (87.4%) | 1796 (83.1%) | |
| Other | 105 (12.6%) | 365 (16.9%) | |
| Missing: 0 | Missing: 0 | ||
| Race | 0.001 | ||
| White | 795 (95.4%) | 1990 (92.1%) | |
| Non-white | 38 (4.6%) | 171 (7.9%) | |
| Missing: 0 | Missing: 0 | ||
| Ethnicity | 0.281 | ||
| Non-Hispanic | 781 (94.0%) | 1967 (92.9%) | |
| Hispanic | 50 (6.0%) | 151 (7.1%) | |
| Missing: 2 | Missing: 43 | ||
| Totally family income per year | 0.020 | ||
| Less than US$25 000 | 66 (13.2%) | 264 (18.1%) | |
| US$5000–US$99 999 | 259 (51.9%) | 745 (51.2%) | |
| US$100 000–US$249 999 | 149 (29.9%) | 401 (27.6%) | |
| US$250 000 or more | 25 (5.0%) | 45 (3.1%) | |
| Missing: 334 | Missing: 706 | ||
| Highest level of education completed | <0.001 | ||
| High school or less and technical/vocational school | 74 (9.0%) | 277 (13%) | |
| Some college | 117 (14.2%) | 368 (17.3%) | |
| College | 341 (41.4%) | 885 (41.7%) | |
| Graduate school | 292 (35.4%) | 593 (27.9%) | |
| Missing: 9 | Missing: 38 | ||
| Marital status | 0.978 | ||
| Married or in a relationship | 795 (95.8%) | 2056 (95.8%) | |
| Divorced/single | 35 (4.2%) | 90 (4.2%) | |
| Missing: 3 | Missing: 15 |
| Pregnancy details | Median (IQR) / N (%) | Median (IQR) / N (%) | P value |
| Parity | 0.622 | ||
| 1 | 753 (90.4%) | 1966 (91.0%) | |
| >1 | 80 (9.6%) | 195 (9.0%) | |
| Missing: 0 | Missing: 0 | ||
| Mode of delivery | 0.731 | ||
| Vaginal birth | 284 (34.4%) | 747 (35.1%) | |
| Caesarean section | 542 (65.6%) | 1384 (64.9%) | |
| Missing: 7 | Missing: 30 | ||
| Gestational age at delivery (weeks+days) | 35+2 (32+1; 38+3) | 34+5 (31+1; 37+3) | 0.566 |
| <28+0 | 99 (12.2%) | 266 (12.6%) | |
| 28+0–31+6 | 117 (14.4%) | 334 (15.8%) | |
| 32+0–36+6 | 306 (37.6%) | 815 (38.5%) | |
| ≥37+0 | 291 (35.8%) | 704 (33.2%) | |
| Missing: 20 | Missing: 42 | ||
| Year of delivery | <0.001 | ||
| Before 2011 | 187 (22.4%) | 623 (28.8%) | |
| 2011–2013 | 174 (20.9%) | 456 (21.1%) | |
| 2014–2016 | 286 (34.3%) | 507 (23.5%) | |
| From 2017 onwards | 186 (22.3%) | 574 (26.6%) | |
| Missing: 0 | Missing: 1 | ||
| Pregnancy outcome | 0.238 | ||
| Living child | 746 (89.6%) | 1931 (89.4%) | |
| Live birth with subsequent infant death | 52 (6.2%) | 119 (5.5%) | |
| Stillbirth(s) | 33 (4.0%) | 88 (4.1%) | |
| Miscarriage | 0 (0%) | 1 (0%) | |
| Induced pregnancy termination | 2 (0.2%) | 22 (1%) | |
| Missing: 0 | Missing: 0 | ||
| Birth weight child (grams) | 2359 (1,452; 3,039) | 2268 (1,406; 3,036) | 0.188 |
| Missing=14 | Missing: 56 | ||
| Maternal ICU-admittance | 156 (19.6%) | 413 (20.2%) | 0.730 |
| Missing: 37 | Missing: 114 | ||
| Baby admitted to the NICU | 456 (58.6%) | 1208 (60.6%) | 0.334 |
| Missing: 55 | Missing: 168 |
ICU, intensive care unit; NICU, neonatal intensive care unit.