Comparison of risk factors for gestational hypertension and preeclampsia in Japanese singleton pregnancies

Aim: To demonstrate the difference between risk factors for gestational hypertension (GH) and preeclampsia (PE). Material and Methods: Using data from women with no essential hypertension and with singleton births between 2001 and 2005 delivering after 22 weeks of gestation at 125 centers in Japan (Japan Perinatal Registry Network) (n = 241 292), we compared risk factors for GH and PE. Odds ratios were calculated using multivariate logistic regression analyses. Results: Of 241 292 women, 2808 (1.2%) developed GH and 6423 (2.7%) developed PE. Thirty-five years or older, primiparity, diabetes mellitus, and renal disease increased the risk of both hypertensive conditions. Forty years or older was a risk factor only for GH, while primiparity, female baby, and renal disease were risk factors only for PE. Early-onset was a common risk factor for small-for-gestational-age (SGA) in GH and PE, but in late-onset only PE was a risk factor for SGA. The main population of SGA infants was composed of PE cases because PE accounted for 83.3% of early-onset type before 32 weeks. Girl preponderance in the PE women was observed (sex ratio: boys/girls = 0.904), while slight boy preponderance was seen in normotensive women (1.06) and GH (1.02). Conclusion: Preeclampsia is associated with lower fetal sex ratio (girl preponderance) compared to GH or normotensive. Presence of hypertension is a risk factor for SGA in early-onset GH and PE, and hypertension and proteinuria are risk factors for SGA in late-onset group.