Table 1.
Maternal baseline characteristics according to pre-pregnancy BMI.
| BMI categories* | Total (N = 669,101) | ||||
|---|---|---|---|---|---|
| Underweight (N = 136,287) |
Normal (N = 448,439) |
Overweight (N = 69,819) |
Obesity (N = 14,556) |
||
| Region (N, %) | |||||
| Non-Pearl river delta | 88,056(64.6) | 284,469(63.4) | 37,907(54.3) | 7846(53.9) | 418,278(62.5) |
| Pearl River delta | 48,231(35.4) | 163,970(36.6) | 31,912(45.7) | 6710(46.1) | 250,823(37.5) |
| Migrant population (N, %) | |||||
| Yes | 12,634(9.3) | 47,452(10.6) | 6763(9.7) | 1367(9.4) | 68,216(10.2) |
| No | 123,653(90.7) | 400,987(89.4) | 63,056(90.3) | 13,189 (90.6) | 600,885(89.8) |
| Age at baseline (N, %) | |||||
| 19–24 years | 57,661(42.3) | 163,489(36.5) | 20,568(29.5) | 4185(28.8) | 245,903(36.8) |
| 25–29 years | 62,836(46.1) | 192,562(42.9) | 27,301(39.1) | 5637(38.8) | 288,336(43.1) |
| 30–34 years | 12,781(9.4) | 65,234(14.6) | 14,023(20.1) | 3067(21.1) | 95,105(14.2) |
| 35–39 years | 2710(2.0) | 23,373(5.2) | 6580(9.4) | 1402(9.6) | 34,065(5.1) |
| 40–50 years | 299(0.2) | 3781(0.8) | 1347(1.9) | 265(1.8) | 5692(0.9) |
| Education (N, %) | |||||
| Primary school or below | 2551(1.9) | 9416(2.1) | 2043(2.9) | 538(3.7) | 14,548(2.2) |
| Junior high school | 55,635(40.8) | 194,653(43.4) | 34,251(49.1) | 7551(51.9) | 292,090(43.7) |
| Senior high school | 33,403(24.5) | 108,876(24.3) | 16,054(23.0) | 3364(23.1) | 161,697(24.2) |
| College or above | 44,698(32.8) | 135,494(30.2) | 17,471(25.0) | 3103(21.3) | 200,766(30.1) |
| Occupation (N, %) | |||||
| Farmer | 52,157(38.3) | 179,447(40.0) | 31,073(44.5) | 6852(47.1) | 269,529(40.3) |
| Worker | 30,365(22.3) | 100,247(22.4) | 15,583(22.3) | 3283(22.6) | 149,478(22.3) |
| Servicer | 21,044(15.4) | 69,247(15.4) | 9775(14.0) | 1992(13.7) | 102,058(15.3) |
| Others | 32,721(24.0) | 99,498(22.2) | 13,388(19.2) | 2429(16.7) | 148,036(22.1) |
| Ethnicity (N, %) | |||||
| Han | 131,068(96.2) | 432,388(96.4) | 67,372(96.5) | 14,024(96.4) | 644,852(96.4) |
| Other | 5219(3.8) | 16,051(3.6) | 2447(3.5) | 532(3.7) | 24,249(3.6) |
| History of pregnancy and adverse pregnancy outcomes (N, %) | |||||
| History of preterm | 302 (0.2) | 1252(0.3) | 302(0.4) | 63(0.4) | 1919(0.3) |
| History of miscarriage | 3248(2.4) | 12,121(2.7) | 2563(3.7) | 580(4.0) | 18,512(2.8) |
| History of induced abortion | 12,926(9.5) | 45,913(10.2) | 8867(12.7) | 1907(13.1) | 69,613(10.4) |
| History of stillbirth | 793(0.6) | 3424(0.8) | 845(1.2) | 216(1.5) | 5278(0.8) |
| History of birth defect | 216(0.2) | 1099(0.3) | 286(0.4) | 64(0.4) | 1665(0.7) |
| First pregnancy♯ | 101,560(74.5) | 296,296(66.1) | 34,424(49.3) | 6876(52.3) | 439,156(65.6) |
| Primipara♯ | 22,055(16.2) | 117,577(26.2) | 30,336(43.5) | 6538(44.9) | 176,506(26.4) |
| Lifestyle before pregnancy (N, %) | |||||
| Active smoke♯ | 372(0.3) | 962(0.2) | 207(0.3) | 62(0.4) | 1603(0.2) |
| Passive smoke♯ | 25,904(19.0) | 77,543(17.3) | 10,615(15.2) | 2081(14.3) | 116,143(17.4) |
| Alcohol♯ | 8089(5.9) | 28,953(6.5) | 3908(5.6) | 697(4.8) | 41,647(6.2) |
| Husband smoke♯ | 39,916(29.3) | 116,958(26.1) | 19,819(28.4) | 4402(30.2) | 181,095(27.1) |
| Lifestyle during early pregnancy (N, %) | |||||
| Active smoke♯ | 465(0.3) | 1438(0.3) | 253(0.4) | 55(0.4) | 2211(0.3) |
| Alcohol# | 759(0.6) | 2440(0.5) | 351(0.5) | 73(0.5) | 3623(0.5) |
| Husband smoke♯ | 20,422(15.0) | 65,014(14.5) | 10,545(15.1) | 2348(16.1) | 98,329(14.7) |
♯Missing data existed.
*The distributions of BMI categories with respect to different baseline characteristics were all statistically (P < 0.05), except for ethnicity, smoking, drink during the early stage of pregnancy.