Table 3.
Pre-pregnancy BMI, BMI at age 18, and weight change since age 18 and relative risk (RR) of spontaneous abortion and stillbirth.
| Spontaneous Abortions (fetal losses < 20 weeks) | Stillbirths (fetal losses ≥ 20 weeks) | |||||
|---|---|---|---|---|---|---|
| Cases/Total | % | Fully-Adjusted RR (95% CI)* | Cases/Total | % | Fully-Adjusted RR (95% CI)* | |
| Prepregnancy BMI | ||||||
| Underweight (<18.5 kg/m2) | 159/1037 | 15.3 | 1.01 (0.87, 1.17) | 4/831 | 0.5 | 0.57 (0.21, 1.54) |
| Normal weight (18.5–24.9 kg/m2) | 2945/18348 | 16.1 | 1.00 (REF) | 131/14492 | 0.9 | 1.00 (REF) |
| Overweight (25–29.9 kg/m2) | 781/4282 | 18.2 | 1.07 (1.00, 1.15) | 38/3289 | 1.2 | 1.17 (0.82, 1.68) |
| Class I Obese(30–34.9 kg/m2) | 251/1376 | 18.2 | 1.06 (0.94, 1.18) | 22/1070 | 2.1 | 2.04 (1.30, 3.20) |
| Class II & III Obese (35+ kg/m2) | 153/676 | 22.6 | 1.24 (1.08, 1.43) | 10/475 | 2.1 | 1.99 (1.05, 3.79) |
| P for Trend | 0.004 | < 0.001 | ||||
| BMI at Age 18 | ||||||
| Underweight (<18.5 kg/m2) | 670/3935 | 17.0 | 1.02 (0.94, 1.09) | 23/3087 | 0.8 | 0.73 (0.47, 1.13) |
| Normal weight (18.5–24.9 kg/m2) | 3235/19463 | 16.6 | 1.00 (REF) | 157/15271 | 1.0 | 1.00 (REF) |
| Overweight (25–29.9 kg/m2) | 266/1648 | 16.1 | 0.94 (0.84, 1.06) | 18/1283 | 1.4 | 1.27 (0.78, 2.05) |
| Obese (30+ kg/m2) | 84/493 | 17.0 | 0.98 (0.81, 1.19) | 6/379 | 1.6 | 1.31 (0.58, 2.94) |
| P for Trend | 0.30 | 0.06 | ||||
| Weight Change from Age 18 | ||||||
| Lost ≥ 4 kg | 246/1947 | 12.6 | 0.78 (0.68, 0.88) | 21/1575 | 1.3 | 1.32 (0.77, 2.25) |
| Stable | 1415/8879 | 15.9 | 1.00 (REF) | 60/7047 | 0.9 | 1.00 (REF) |
| Gained 4–9.9 kg | 1389/8332 | 16.7 | 1.01 (0.94, 1.08) | 50/6515 | 0.8 | 0.87 (0.60, 1.27) |
| Gained 10–19.9 kg | 812/4437 | 18.3 | 1.05 (0.97, 1.13) | 46/3438 | 1.3 | 1.37 (0.93, 2.02) |
| Gained ≥ 20 kg | 393/1944 | 20.2 | 1.09 (0.98, 1.20) | 27/1445 | 1.9 | 1.77 (1.11, 2.82) |
| P for Trend | < 0.001 | 0.04 | ||||
Abbreviations: BMI, body mass index; RR, relative risk.
*
Models are adjusted for age (continuous), smoking status (never, former, current, missing), physical activity (< 3 MET-h/wk, 3–8.9 MET-h/wk, 9–17.9 MET-h/wk, 18–26.9 MET-h/wk, 27–41.9 MET-h/wk, >42 MET-h/wk, and missing), year of pregnancy (continuous), history of infertility (no, yes, and missing), current multivitamin use (no, yes, missing), marital status (married, not married), and race (white, other). Weight change models are further adjusted for height (continuous).