A recent study has revealed a significant association between exposure to fine particulate matter (PM2.5) and an increased risk of gestational diabetes mellitus (GDM), a prevalent metabolic disorder of pregnancy. GDM poses serious health risks for both mothers and infants, including neonatal hypoglycemia and macrosomia.
The mechanisms through which PM2.5 contributes to GDM are not fully understood. Existing research suggests that polycyclic aromatic hydrocarbons (PAHs) within PM2.5 might lead to insulin resistance by inhibiting the insulin receptor substrate 2 gene. Additionally, PM2.5 can disrupt the CC-chemokine receptor 2 signaling pathway, further exacerbating insulin resistance. However, other studies have failed to establish a clear link between PM2.5 and GDM, indicating the need for larger-scale investigations.
PM2.5 comprises various components, including sulfate, nitrate, organic matter (OM), ammonium, and black carbon (BC), each with differing toxicity levels. While some research attributes asthma to ammonia and diabetes risk to OM, comprehensive studies on GDM risk and PM2.5 constituents remain limited.
Study Overview
The retrospective study, conducted in Guangzhou City, Guangdong Province, China, analyzed the relationship between PM2.5 exposure and GDM risk among pregnant women. Data were collected from 2020 to 2022 using local hospital records and the 10th revision of the International Classification of Diseases (ICD-10) for GDM diagnosis.
Participants included women who conceived naturally, lived in Guangzhou during their pregnancy, and had complete data. They were not carrying twins and had no prior history of hypertension or diabetes. Information on daily PM2.5 concentrations and its constituents was obtained from the Tracking Air Pollution in China (TAP) project database, along with data on potential confounding factors such as age, ethnicity, and occupation.
GDM was diagnosed through an oral glucose tolerance test performed between the 24th and 28th weeks of pregnancy.
Findings
The study involved 17,855 pregnant women, with 22.1% diagnosed with GDM. The median age of participants was 29, and approximately 15% were of advanced maternal age. Women with GDM had higher median exposure levels to PM2.5, sulfate, and OM compared to those without GDM. A robust correlation was found among PM2.5, OM, BC, sulfate, nitrate, and ammonium concentrations, confirmed by sensitivity analyses.
After adjusting for confounding factors, higher PM2.5 exposure during the first trimester was associated with a 9.2% increased risk of GDM. Specific constituents contributed varying risks: sulfate (8.6%), nitrate (11.6%), ammonium (11.1%), OM (9.7%), and BC (8.5%). Increased risk was also noted with exposure to these components between the first and second trimesters and during the second trimester alone.
Inflection points for GDM risk related to PM2.5, OM, and BC were lowest during the second trimester, while sulfate, nitrate, and ammonium had lowest inflection points from the first to second trimester. Non-linear relationships were observed for OM, ammonium, nitrate, and PM2.5 in the first trimester.
Significant associations with GDM risk were identified across several subgroups, including those with anemia, non-primiparous women, and specific infant sexes. Variations in risk were noted between trimesters and age subgroups.
Conclusions
Exposure to black carbon and sulfate during the second trimester appears to reduce GDM risk, whereas PM2.5 and its constituents at other pregnancy stages are linked to increased GDM risk. Identifying these critical exposure periods can inform public health strategies aimed at preventing GDM and mitigating its adverse effects on maternal and infant health.
