Maternal exposure to PM2.5 and its components and risk of small for gestational age in women undergoing in vitro fertilization: a propensity score-matched case-control study in Guangzhou, China

Pregnant women conceiving via in vitro fertilization (IVF) represent a uniquely vulnerable population, yet the impact of ambient fine particulate matter (PM 2.5 ) and its specific chemical components on their fetal growth remains under-researched. This study aimed to investigate the associations between prenatal exposure to PM 2.5 and its key components—sulfate (SO 4 2− ), nitrate (NO 3 − ), ammonium (NH4 + ), organic matter (OM), and black carbon (BC)—with the risk of small for gestational age (SGA) in IVF pregnancies. A propensity score-matched case-control study was conducted in Guangzhou, China. From a source population of 1,459 women who conceived via IVF, 166 SGA cases were identified and matched 1:1 with controls. Exposure to PM 2.5 and its components was estimated using time-weighted average concentrations for each trimester and the entire pregnancy. Logistic regression models adjusted for potential confounders were used to estimate odds ratios (ORs), and mixture analyses were employed to identify the dominant pollutants driving the observed risks. Exposure to PM 2.5 during the second trimester (OR = 1.082, 95% CI: 1.005–1.165) and third trimester (OR = 1.075, 95% CI: 1.002–1.154), and the entire pregnancy (OR = 1.124, 95% CI: 1.015–1.245) was significantly associated with an increased risk of SGA. Significant positive associations were also observed for SO 4 2− , OM, and BC. Notably, mixture analyses identified NO 3 − as the primary driver of SGA risk. Furthermore, subgroup analyses revealed no significant associations with these pollutants. Prenatal exposure to PM 2.5 and its components, particularly secondary inorganic aerosols and carbonaceous species, is significantly associated with impaired fetal growth in IVF-conceived pregnancies. These findings emphasize the need for component-specific air quality guidelines and targeted interventions to protect this high-risk population during critical gestational windows.