Parental age and age gap in relation to neonatal health: a cohort study in eastern China.

Objective: To investigate the association between parental age, age gap, and neonatal health outcomes, and to provide epidemiological evidence for preconception counseling and perinatal risk assessment. Methods: This retrospective cohort study included mother-infant pairs who delivered at the Women's Hospital, Zhejiang University School of Medicine between January 2016 and December 2022. A total of 15,762 pairs were analyzed, comprising 7,557 healthy controls and 8,205 cases. The primary exposure was parental age comparison. Multivariable logistic regression was used to examine the association between parental age comparison and neonatal diseases, with adjustment for maternal BMI, hypertension, diabetes, gestational week, smoking, alcohol use, and educational level. Parental ages were also entered as continuous variables, and interaction terms were tested. Restricted cubic splines were applied to assess nonlinear dose-response relationships. Results: Compared with the equal-age group, both the father-older group (OR = 1.561, 95% CI: 1.203-3.201) and the mother-older group (OR = 1.652, 95% CI: 1.323-2.343) had significantly increased odds of neonatal diseases. After further adjustment for individual parental ages, the father-older association became non-significant (OR = 1.121, Conclusion: Both maternal and paternal ages are independent risk factors with nonlinear dose-response relationships. The combined structure of parental ages should be considered in preconception counseling and perinatal risk assessment.