TABLE 4.
Association between maternal prepregnancy BMI category and stillbirth defined by probable and possible cause1
| Cause of stillbirth/prepregnancy BMI category | Cases, n | Unadjusted rate2 per 1000 live-born and stillborn infants (95% CI) | Unadjusted HR (95% CI) | Adjusted3 HR (95% CI) |
| Abruption | ||||
| Lean | 89 | 2.3 (1.8, 2.9) | 1.0 (reference) | 1.0 (reference) |
| Overweight | 39 | 2.6 (1.7, 3.5) | 1.1 (0.7, 1.7) | 1.1 (0.7, 1.8) |
| Obese | 25 | 3.4 (1.8, 4.9) | 1.4 (0.9, 2.4) | 1.4 (0.8, 2.4) |
| Severely obese | 20 | 3.8 (2.0, 5.6) | 1.6 (1.0, 2.7) | 1.3 (0.8, 2.4) |
| Placental disease | ||||
| Lean | 70 | 1.8 (1.4, 2.3)* | 1.0 (reference) | 1.0 (reference) |
| Overweight | 37 | 2.4 (1.6, 3.2) | 1.3 (0.8, 2.0) | 1.3 (0.9, 2.1) |
| Obese | 25 | 3.8 (2.2, 5.4) | 2.1 (1.2, 3.4) | 2.0 (1.2, 3.4) |
| Severely obese | 25 | 4.5 (2.5, 6.5) | 2.4 (1.5, 4.1) | 2.3 (1.3, 3.9) |
| Obstetric complications | ||||
| Lean | 73 | 2.0 (1.5, 2.5) | 1.0 (reference) | 1.0 (reference) |
| Overweight | 41 | 2.4 (1.6, 3.2) | 1.2 (0.8, 1.8) | 1.2 (0.8, 1.9) |
| Obese | 20 | 2.8 (1.4, 4.3) | 1.4 (0.8, 2.4) | 1.3 (0.7, 2.4) |
| Severely obese | 17 | 3.3 (1.6, 5.0) | 1.6 (0.9, 2.9) | 1.4 (0.7, 2.5) |
| Infection | ||||
| Lean | 58 | 1.6 (1.2, 2.0) | 1.0 (reference) | 1.0 (reference) |
| Overweight | 33 | 1.9 (1.2, 2.6) | 1.2 (0.8, 1.9) | 1.2 (0.7, 1.9) |
| Obese | 21 | 3.0 (1.5, 4.5) | 1.8 (1.0, 3.3) | 1.8 (0.9, 3.2) |
| Severely obese | 11 | 2.3 (0.9, 3.7) | 1.4 (0.7, 2.8) | 1.1 (0.6, 2.3) |
| Maternal medical condition | ||||
| Lean | 38 | 1.0 (0.7, 1.4)* | 1.0 (reference) | 1.0 (reference) |
| Overweight | 28 | 1.7 (1.0, 2.4) | 1.7 (1.0, 2.8) | 1.6 (1.0, 2.8) |
| Obese | 17 | 2.5 (1.2, 4.0) | 2.4 (1.3, 4.4) | 2.2 (1.2, 4.2) |
| Severely obese | 22 | 4.0 (2.2, 5.8) | 3.9 (2.2, 6.8) | 3.2 (1.7, 5.8) |
| Fetal genetic or structural abnormality | ||||
| Lean | 46 | 1.2 (0.8, 1.5)* | 1.0 (reference) | 1.0 (reference) |
| Overweight | 21 | 1.5 (0.8, 2.1) | 1.3 (0.7, 2.2) | 1.3 (0.7, 2.3) |
| Obese | 19 | 2.5 (1.1, 3.9) | 2.1 (1.1, 4.0) | 2.2 (1.1, 4.2) |
| Severely obese | 13 | 2.6 (1.1, 4.1) | 2.2 (1.1, 4.3) | 2.2 (1.1, 4.4) |
| Umbilical cord abnormality | ||||
| Lean | 25 | 0.6 (0.4, 1.0)* | 1.0 (reference) | 1.0 (reference) |
| Overweight | 23 | 1.3 (0.7, 1.9) | 1.9 (1.0, 3.6) | 1.8 (1.0, 3.5) |
| Obese | 15 | 2.4 (1.1, 3.7) | 3.5 (1.8, 7.0) | 3.3 (1.6, 6.6) |
| Severely obese | 9 | 1.7 (0.5, 2.8) | 2.4 (1.1, 5.4) | 2.0 (0.9, 4.5) |
1
BMI (in kg/m2): lean, <25; overweight, 25 to <30; obese, 30 to <35; and severely obese, ≥35. *P < 0.05 based on a Pearson χ2 test of independence adjusted for the case-cohort design.
2
Based on the weighted cohort.
3
Adjusted for maternal race-ethnicity, maternal age, maternal education, parity, smoking during pregnancy, marital status, and trimester of entry to prenatal care.