Prenatal air pollutant exposure and preterm birth risk in primiparas of advanced maternal age residing in rural Henan province

Direct evidence on the impact of air pollution on preterm birth (PTB) among advanced maternal age (AMA) primiparas is limited. This study examined the association between air pollution and PTB among 6,295 AMA primiparas in rural Henan Province. Logistic regression and distributed lag nonlinear models showed that prenatal exposure to carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and fine particulate matter (PM_2.5) was associated with an increased PTB risk among AMA primiparas, while ozone (O₃) exposure was inversely related to PTB risk (all <i>P</i> < 0.05). Moreover, the vulnerable periods were identified as gestational weeks 1-6 and 22-28. The education level, smoking status, and season of conception significantly modified the association between PTB and air pollution (<i>P</i> _interaction < 0.10) among AMA primiparas. These findings emphasize the impact of air pollution on PTB risk in AMA primiparas, highlighting the need for targeted interventions in vulnerable populations.