Prenatal PM2.5 exposure linked to spontaneous PTB risk

Prenatal PM2.5 exposure linked to spontaneous PTB risk | Image Credit: © ttlsc - © ttlsc - stock.adobe.com.

The risk of spontaneous preterm birth (sPTB) is increased by prenatal exposure to fine particulate matter (PM2.5) and certain constituents, according to a recent study published in JAMA Network Open.¹

Approximately 11% of births worldwide are preterm birth, which has been identified as the leading cause of death among children aged under 5 years. Of preterm births, approximately 60% to 70% are spontaneous.² A lack of understanding about the causes of uterine quiescence disruption makes it difficult to predict sPTB in pregnant patients.¹

The significant risks of neonatal morbidity and mortality linked to sPTB make it vital to identify risk factors. As PM2.5 exposure has been linked to pathophysiological pathways, investigators have hypothesized an association with sPTB, but research remains limited.

To evaluate the association of prenatal PM2.5 and PM2.5 constituent exposure with sPTB, investigators conducted a retrospective cohort study. Singleton live births within the Kaiser Permanente Southern California health care system (KPSC) between January 1, 2008, and December 31, 2018, were included in the analysis.

KPSC electronic health records were assessed for medical and obstetric histories, sociodemographic characteristics, residential histories, birth records, and health-related behaviors. Race and ethnicity were determined based on administrative and self-reported data.

Preterm birth was defined as a live birth occurring after 20 weeks’ gestation but before 37 weeks’ gestation. Frist-trimester ultrasonography was utilized to determine gestational age in most participants, though some had gestational age determined by last menstrual period and second-trimester ultrasonography.

Investigators defined sPTB as “a preterm delivery that follows the spontaneous onset of labor, is not indicated by concomitant pregnancy complications, and occurs within 7 days of the last preterm labor visit.” Remaining preterm births with medical indications were grouped as iatrogenic preterm births (iPTBs).

A validated ensemble model was used to collect daily total PM2.5 concentrations at a census tract level from 2007 to 2018. Patients’ residential history and geocoded address during pregnancy were assessed to determine mean exposures to PM2.5 and PM2.5 constituents based on each trimester and the full prenatal period.

There were 409,037 singleton live births included in the final analysis. Participants were aged a mean 30.3 years at delivery, and 12.46% were Asian, 7.70% Black, 51% Hispanic, and 26.22% White.

Of live births, 4.73% were sPTB and 2.75% were iPTB. These births were more common among mothers who were older, Black or Asian, overweight, with a lower educational level, with pregestational diabetes and hypertension, and with a history of preterm birth.

A mean prenatal exposure to PM2.5 of 11.40 (2.34) μg/m3 was reported among all births vs 11.54 (2.04) μg/m3 among sPTBs. An adjusted odds ratio (aOR) of 1.15 was reported for sPTB with each IQR increase in total PM2.5 exposure, defined as an increase of 2.76 μg/m3. Additionally, the aOR increased by 1.05 for each increase of 1 μg/m3.

PM2.5 constituents linked to increased risks of sPTB included sulfate, nitrate, organic matter, and black carbon, with aORs of 1.06, 1.09, 1.05, and 1.15, respectively, per IQR increase. Higher aORs were reported for exposure during the second trimester, with aORs for total PM2.5 concentration being 1.07 for the first trimester, 1.10 for the second, and 1.09 for the third.

These results indicated increased sPTB risk from exposure to PM2.5 during pregnancy. Investigators concluded improved green space exposure may be utilized to mediate the link between prenatal PM2.5 exposure and sPTB.

References

1. Jiao A, Reilly AN, Benmarhnia T, et al. Fine particulate matter, its constituents, and spontaneous preterm birth. JAMA Netw Open. 2024;7(11):e2444593. doi:10.1001/jamanetworkopen.2024.44593
2. Goldenberg RL, Culhane JF, Iams JD, Romero R. Epidemiology and causes of preterm birth.Lancet. 2008;371(9606):75-84. doi:10.1016/S0140-6736(08)60074-4