Investigating the Synergistic Interaction of Maternal Gestational Hypertension and Chlamydia Infection on the Use of Antibiotics for Newborns.

Objective: Maternal gestational hypertension and chlamydia infection are recognized as common diseases of pregnancy, which are associated with an increased risk of antibiotic usage for newborns. Our study aimed to evaluate the association between co-existing maternal gestational hypertension and chlamydia infection during pregnancy and the risk of neonatal antibiotic use. Methods: Our study included 3 383 942 eligible subjects from the National Vital Statistics System (NVSS) database in 2019. Clinical characteristics, including a history of pre-pregnancy diabetes and hypertension, pregnancy complications, pregnancy infections, etc. were collected. Multivariate logistic regression analyses were used to examine the association between maternal gestational hypertension and chlamydia infection and the risk of the use of antibiotics for newborns. Simultaneously, we adopted attributable proportion (AP) and synergy index (S) to assess whether the interactions are statistically significant. Results: Of 3 383 942 participants, 61 133 participants had antibiotic use and 3 322 809 did not. After adjusting for all covariates, gestational hypertension [odds ratio (OR) = 1.04; 95% confidence intervals (CI): 1.04-1.04] and chlamydia infection (OR = 1.32, 95% CI: 1.32-1.32) were associated with an increased risk of antibiotic use. Mothers with both gestational hypertension and chlamydia infection (OR = 1.94, 95% CI: 1.72-2.20) had a higher risk of antibiotic usage for newborns. Moreover, the synergistic interaction of gestational hypertension and chlamydia infection was found to be significant (AP = 0.12, 95% CI: 0.01-0.24; S = 1.34, 95% CI: 1.02-1.76). Finally, stratification analyses based on mothers' age elucidated that the interaction was robust among the group with non-advanced maternal age. Conclusion: Synergistic interaction between maternal gestational hypertension and chlamydia infection may significantly increase the risk of antibiotic usage for newborn. However, more studies are required in the future to confirm this association and elucidate the underlying mechanism.