Associations between early-onset and late-onset gestational hypertension and pre-eclampsia and the risk of preterm birth
| Onset period | Preterm birth | |||
| No | Incidence (%) | Crude RR (95% CI) | Adjusted RR (95% CI)* | |
| Gestational hypertension | ||||
| None† | 180 988 | 5.47 | 1 | 1 |
| Early-onset | 849 | 10.72 | 2.08 (1.67 to 2.58) | 2.13 (1.71 to 2.65) |
| Late-onset | 18 266 | 5.40 | 0.99 (0.92 to 1.06) | 1.00 (0.94 to 1.07) |
| Pre-eclampsia | ||||
| None† | 195 191 | 5.44 | 1 | 1 |
| Early-onset | 104 | 31.73 | 8.09 (5.35 to 12.23) | 8.47 (5.59 to 12.80) |
| Late-onset | 4808 | 6.80 | 1.27 (1.13 to 1.42) | 1.30 (1.16 to 1.46) |
*Adjusted for maternal age (continuous), BMI (continuous), education level, occupation, ethnicity, parity and folic acid use.
†Reference group.
BMI, body mass index; RR, risk ratio.