TABLE 3—
Body Mass Index (BMI) in Early Pregnancy and Outcome of First Pregnancy: Cohort of Scottish Women (n = 84 701), 1991–2001
| BMI < 20 | BMI 20–24.9b | BMI 25–29.9 | BMI 30–34.9 | BMI ≥ 35 | |||||
| No. (%) | ORa (95% CI) | No. (%) | No. (%) | ORa (95% CI) | No. (%) | ORa (95% CI) | No. (%) | ORa (95% CI) | |
| Overall preterm delivery | 750 (7.8) | 1.36 (1.25, 1.48) | 2697 (5.9) | 1234 (5.9) | 0.99 (0.93, 1.07) | 404 (6.7) | 1.12 (1.00, 1.25) | 195 (8.0) | 1.34 (1.15, 1.56) |
| Spontaneous preterm delivery | 507 (5.3) | 1.46 (1.32, 1.62) | 1654 (3.6) | 678 (3.3) | 0.89 (0.82, 0.98) | 189 (3.1) | 0.85 (0.73, 0.99) | 73 (3.0) | 0.81 (0.64, 1.03) |
| Elective preterm delivery | 243 (2.5) | 1.16 (1.00, 1.34) | 1043 (2.3) | 556 (2.7) | 1.15 (1.03, 1.27) | 215 (3.6) | 1.52 (1.31, 1.77) | 122 (5.0) | 2.13 (1.75, 2.58) |
| Neonatal death | 31 (0.3) | 1.67 (1.10, 2.54) | 88 (0.2) | 54 (0.3) | 1.35 (0.96, 1.90) | 17 (0.3) | 1.46 (0.86, 2.46) | 13 (0.5) | 2.77 (1.54, 4.99) |
| ELBW infant | 40 (0.4) | 1.35 (0.94, 1.93) | 135 (0.3) | 73 (0.4) | 1.20 (0.90, 1.60) | 26 (0.4) | 1.47 (0.96, 2.24) | 24 (1.0) | 3.31 (2.13, 5.14) |
| ELBW infant surviving to 1 year | 18 (0.2) | 1.02 (0.61, 1.72) | 79 (0.2) | 36 (0.2) | 1.02 (0.69, 1.52) | 15 (0.3) | 1.47 (0.84, 2.56) | 14 (0.6) | 3.36 (1.89, 5.98) |
| Preeclampsia | 208 (2.2) | 0.79 (0.68, 0.91) | 1350 (3.0) | 1025 (4.9) | 1.68 (1.54, 1.82) | 446 (7.4) | 2.57 (2.30, 2.88) | 243 (10.0) | 3.60 (3.12, 4.17) |
Note. OR = odds ratio; CI = confidence interval; ELBW = extremely low birthweight. The total numbers of births across the 5 BMI categories were 9573 (11.3%), 45 812 (54.1%), 20 819 (24.6%), 6060 (7.2%), and 2437 (2.9%), respectively.
aAdjusted for maternal age, height, deprivation category, smoking and marital status, and number of previous spontaneous early pregnancy losses and therapeutic abortions and referent to women with a BMI of 20–24.9.
bReference group.