Study population characteristics in both cohorts stratified by self-reported preterm birth status. Data presented as means (SD) or percentage, unless noted otherwise.
| NHS Preterm Birth | NHSII Preterm Birth | |||
|---|---|---|---|---|
| Yes | No | Yes | No | |
| Participants, n (%) | 3588 (4.2) | 82,727 (95.8) | 7104 (7.2) | 91,027 (92.8) |
| Age at baseline, yrs | 42 (7.1) | 43 (7.1) | 34 (4.7) | 34 (4.7) |
| Pregnant mother smoked* | NA | NA | 27.9 | 20.4 |
| Mother smoked in home** | 24.3 | 20.1 | 36.0 | 30.0 |
| Father smoked in home** | 57.0 | 54.7 | 49.6 | 47.5 |
| BMI at age 18 yrs | 18.7 (7.4) | 19.0 (7.2) | 21.3 (3.5) | 21.3 (3.3) |
| BMI at baseline | 23.5 (4.7) | 23.5 (4.5) | 24.3 (5.4) | 24.1 (5.0) |
| Maternal diabetes | 9.9 | 9.8 | 7.9 | 7.1 |
| Low birth weight, < 5.5 lbs† | 70.6 | 5.4 | 49.2 | 3.4 |
| High birth weight, > 10 lbs† | 0.2 | 2.0 | 0.1 | 1.3 |
| African American | 0.8 | 1.3 | 1.2 | 1.6 |
| Hispanic | 0.7 | 0.6 | 1.3 | 1.5 |
| Current smoker at baseline | 30.0 | 30.7 | 13.3 | 13.0 |
| Past smoker at baseline | 23.5 | 24.6 | 19.1 | 21.6 |