Effects of Interaction Between Gestational Hypertension and History of Preterm Birth on the Risk of Preterm Birth: An Analysis Based on the National Vital Statistics System Database.

BACKGROUND Premature birth is an unsolved social and public problem. We aimed to explore the independent association and interaction effect between gestational hypertension (GH) and the history of preterm birth (HPB) on the risk of preterm birth. MATERIAL AND METHODS A case-control study involving participants with complete birth data was conducted using the United States National Vital Statistics System in 2019. Logistic regression analysis of 3 models were performed with odds ratio (OR) and 95% confidence interval (CI). Relative excess risk of interaction (RERI), attributable proportion of interaction (AP), and synergy index (S) were used to evaluate the interaction between GH and HPB on the risk of preterm birth. RESULTS A total of 2 822 624 participants were examined, with 10.83% in the known preterm birth group and 89.17% in the control group. Following adjustments for covariates, the association between GH and HPB and preterm birth was significant with ORs of 2.604 (95% CI: 2.573-2.635) and 3.047 (95% CI: 2.997-3.097), respectively. Moreover, there was a significant interaction between GH and HPB on preterm birth risk, with an OR of 6.095 (95% CI: 5.847-6.352), RERI of 1.222 (95% CI: 0.965-1.479), AP of 0.201 (95% CI: 0.167-0.235), and S of 1.317 (95% CI: 1.250-1.387), especially in participants with maternal age 20 to 29, 30 to 34, ≥35 years, and single birth. CONCLUSIONS GH and HPB might be positively associated with preterm birth, and there was an additive interaction between GH and HPB on preterm birth, indicating that obstetricians should pay more attention to prevention in this population.