Association of fine particulate matter exposure during pregnancy and stillbirth rates in Pakistan: a cross-sectional study.

Abstract

This study assessed the association between fine particulate matter (PM_2.5) exposure during pregnancy and stillbirth in Pakistan. We hypothesised that higher PM_2.5 exposure is linked to increased stillbirth risk. A cross-sectional study using secondary data from the 2017 to 2018 Pakistan Demographic and Health Survey (PDHS), combined with satellite-derived PM_2.5 exposure data. The study covered urban and rural areas across Pakistan, including all four provinces (Punjab, Sindh, Khyber Pakhtunkhwa and Baluchistan) and administrative regions (Gilgit-Baltistan (GB), Islamabad, Federally Administered Tribal Areas and Azad Jammu Kashmir). The study included 9172 married women aged 15-49 with at least one birth in the past 5 years. Women with incomplete pregnancy outcome data were excluded. PM_2.5 exposure was estimated using satellite data, matching PDHS clusters with the nearest air quality point via MATLAB. Monthly average exposure was categorised into quartiles. Stillbirth, defined as pregnancy loss at ≥28 weeks gestation. Multivariable logistic regression was used to assess the association between PM_2.5 and stillbirth, adjusting for maternal age, gravidity, wealth index, birth interval, previous adverse pregnancy outcome and region of residence. The stillbirth rate in Pakistan for the most recent pregnancy was 17.0 (14.5-19.9) per 1000 births, with highest rates (28.9) in Baluchistan province. The mean level of PM_2.5 exposure in Pakistan was 53.96 (SD 20.42; range 5.9-209.4) µg/m³. PM_2.5 exposure was higher for urban (56.43) than rural (51.87) pregnancies, highest in Sindh (78.06) and lowest in GB (13.41) provinces. For every 1 µg/m³ average increase in PM_2.5 during the pregnancy period, there was approximately 1% increase in stillbirth. Increased PM_2.5 exposure was strongly associated with stillbirth risk. This underscores the need for targeted public health interventions, such as government regulations, emission controls and clean energy initiatives to protect pregnant women in high-risk areas.