Table 1.
Maternal baseline characteristics with respect to pre-pregnancy status of BMI.
| Characteristics | Normal weight | Underweight | Overweight or Obesity | |||
|---|---|---|---|---|---|---|
| Preterm birth (n = 11,994) | Total births (n = 165,172) | Preterm birth (n = 4,373) | Total births (n = 58,220) | Preterm birth (n = 2,245) | Total births (n = 27,865) | |
| Birth weight (grams, Mean (SD)) | 2939.0 (451.3) | 3182.1 (355.1) | 2893.5 (441.2) | 3112.9 (342.8) | 2950.0 (473.3) | 3229.8 (384.1) |
| Maternal age (years, Mean (SD)) | 27.3 (4.6) | 27.3 (4.3) | 25.7 (3.7) | 25.7 (3.5) | 28.9 (5.2) | 28.7 (4.9) |
| Maternal age, n (%) | ||||||
| <25 years | 3,610 (30.1) | 46,755 (28.3) | 1829 (41.8) | 22,933 (39.4) | 499 (22.2) | 5,977 (21.5) |
| 25 ~ 34 years | 7,360 (61.4) | 106,166 (64.3) | 2,414 (55.2) | 33,898 (58.2) | 1,358 (60.5) | 17,956 (64.4) |
| ≥35 years | 1,024 (8.5) | 12,251 (7.4) | 130 (3.0) | 1,389 (2.4) | 388 (17.3) | 3,932 (14.1) |
| Delivery mode, n (%) | ||||||
| Vaginal delivery | 8,433 (70.3) | 118,678 (71.9) | 3,351 (76.6) | 46,035 (79.1) | 1,309 (58.3) | 16,635 (59.7) |
| Cesarean section | 3,561 (29.7) | 46,494 (28.1) | 1,022 (23.4) | 12,185 (20.9) | 936 (41.7) | 11,230 (40.3) |
| Newborn sex, n (%) | ||||||
| Male | 6,735 (56.2) | 86,751 (52.5) | 2,475 (56.6) | 30,202 (51.9) | 1,272 (56.7) | 14,756 (53.0) |
| Female | 5,259 (43.8) | 78,421 (47.5) | 1898 (43.4) | 28,018 (48.1) | 973 (43.3) | 13,109 (47.0) |
| Delivery season, n (%) | ||||||
| Spring(March–May) | 2,563 (21.4) | 35,375 (21.4) | 941 (21.5) | 12,797 (22.0) | 520 (23.2) | 6,106 (21.9) |
| Summer(June–August) | 2,974 (24.8) | 40,131 (24.3) | 1,107 (25.3) | 13,735 (23.6) | 549 (24.4) | 6,936 (24.9) |
| Fall(September–November) | 3,567 (29.7) | 49,110 (29.7) | 1,235 (28.2) | 17,191 (29.5) | 667 (29.7) | 8,161 (29.3) |
| Winter(December–February) | 2,890 (24.1) | 40,556 (24.6) | 1,090 (24.9) | 14,497 (24.9) | 509 (22.7) | 6,662 (23.9) |
| History of adverse pregnancy outcomes, n (%) | ||||||
| History of preterm | 122 (1.0) | 820 (0.5) | 31 (0.7) | 182 (0.3) | 37 (1.6) | 200 (0.7) |
| History of stillbirth | 137 (1.1) | 1816 (1.1) | 32 (0.7) | 445 (0.8) | 59 (2.6) | 450 (1.6) |
| History of miscarriage | 495 (4.1) | 6,644 (4.0) | 148 (3.4) | 1836 (3.2) | 132 (5.9) | 1,534 (5.5) |
| History of induced abortion | 1,595 (13.3) | 23,860 (14.4) | 471 (10.8) | 6,849 (11.8) | 409 (18.2) | 5,007 (18.0) |
| Lifestyle during early pregnancy a, n (%) | ||||||
| Active smoke | 78/11751 (0.7) | 879/161677 (0.5) | 24/4286 (0.6) | 386/57010 (0.7) | 14/2200 (0.6) | 155/27241 (0.6) |
| Husband smoke | 2415/11713 (20.6) | 33,546/161431 (20.8) | 909/4249 (21.4) | 12,595/56822 (22.2) | 482/2201 (21.9) | 6355/27193 (23.4) |
| Alcohol | 116/11744 (1.0) | 1672/161580 (1.0) | 41/ 4,284 (1.0) | 584/56980 (1.0) | 26/2200 (1.2) | 284/27230 (1.0) |
a
Denominators provided as missing data existed.