Low interpregnancy interval and air pollution have synergistic effect on Low Birth Weight outcomes, claims study
Researchers found that short interpregnancy intervals and exposure to air pollution during pregnancy are two risk factors for low birth weight (LBW). Recently, a research study was conducted in Nantong, China, to explore the combined effects of IPI with air pollution exposure on birth weights. The investigation showed that shorter IPIs are synergistic with high levels of air pollutants, therefore implying that optimizing birth spacing and controlling air pollution will improve birth outcomes. The study was published in BMC Public Health by Lu X. and colleagues.
This was a retrospective cohort study based on birth records from Jiangsu Maternal Child Information System that focused on the live births in Nantong from January 2020 to June 2021. According to the definition, IPI was considered as time elapsed from the delivery of a previous live birth up to the date of the last menstrual period of the subsequent pregnancy. The above was estimated based on a hybrid kriging-LUR-RF model for exposure to ambient air pollutants during pregnancy, including PM2.5 and PM10, ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). An innovative air pollution score was generated by summing the concentrations of five pollutants, weighted by LBW regression coefficients, excluding CO.
A total of five multivariate logistic regression models were applied to analyze the impacts of IPI, air pollution, and their interaction on LBW, including an interaction of IPI and PM2.5 in terms of RERI, AP, and S, which were calculated to quantify the additive interaction effect.
Results
The study had analyzed 10,512 singleton live births with an LBW rate of 3.7%. The association between IPI and LBW followed an L-shaped risk curve, which indicated that a shorter IPI was linked to higher LBW risk. Exposure to air pollutants during pregnancy increased the risk of LBW. For each interquartile range increase in air pollutant levels, the ORs for LBW were
• PM2.5: OR = 1.16 (95% CI: 1.01-1.32)
• PM10: OR = 1.30 (95% CI: 1.06-1.59)
• Ozone (O3): OR = 1.22 (95% CI: 1.06-1.41)
• Air pollution score: OR = 1.32 (95% CI: 1.10-1.60)
In the first trimester, the study reported a high additive interaction between IPI and PM2.5 exposure. The highest risk of LBW, such as compared to pregnancies with normal IPI and low PM2.5 exposure, was found among those with a short IPI and high PM2.5 exposure, which presented a relative risk of 3.53 (95% CI: 1.85-6.49).
This study presents a synergistic effect of short interpregnancy intervals and air pollution on low birth weight, highlighting both the rational spacing of births and the control of air pollution as crucial points to increase the birth outcomes. Addressing these factors as a whole would make pivotal progress in developing means by which the incidence of LBW could be reduced and healthier pregnancies supported.
Reference:
Lu, X., Zhang, Y., Jiang, R., Qin, G., Ge, Q., Zhou, X., Zhou, Z., Ni, Z., & Zhuang, X. (2024). Interpregnancy interval, air pollution, and the risk of low birth weight: a retrospective study in China. BMC Public Health, 24(1). https://doi.org/10.1186/s12889-024-19711-3
