Research finds particulate pollution during pregnancy may impact newborn kidney function

In a recent cohort study published in the journal eBioMedicine, researchers investigated the potential effect of gestational exposure to particulate air pollution on cord blood cystatin C levels, a marker for kidney function.

They found that increased exposure to black carbon and fine particulate matter during pregnancy, particularly in the third trimester, was associated with higher cord blood cystatin C levels, suggesting potential negative effects on newborn kidney function.

Study: Newborn glomerular function and gestational particulate air pollution. Image Credit: Deemerwha studio/Shutterstock.com

Background

Researchers have previously hypothesized that a lower number of nephrons at birth increases the risk of hypertension, and early environmental exposures can have a long-term impact on health. Optimal kidney function is critical for maintaining body homeostasis.

However, assessing kidney function in neonates is challenging. Cystatin C, a protein produced by nucleated cells and filtered by the kidneys, has emerged as a valuable marker for glomerular filtration in newborns, as it is not influenced by muscle mass or inflammation.

Ambient air pollution, especially particulate matter of diameter <2.5 micrometers (PM2.5) and black carbon (BC), is a significant contributor to global disease, linked to cardiovascular, respiratory, and kidney issues. PM2.5 is known to cause cardiovascular problems, which are closely related to kidney health.

Maternal exposure to PM2.5 is shown to be associated with higher blood pressure and lower birth weight in newborns, potentially affecting kidney development.

While studies have shown that air pollution increases cystatin C levels and decreases glomerular filtration in adults, there is a lack of research on its effects on cystatin C levels in newborns, highlighting a gap in understanding the early-life impact of pollution on kidney function.

Therefore, researchers in the present study investigated whether cystatin C levels are altered in the cord blood plasma of neonates owing to exposure to ambient air pollution, specifically BC and PM2.5.

About the study

In the present study, medical and lifestyle data of 1,484 healthy mother-newborn pairs with singleton pregnancies between 2010 and 2020 were obtained from the ENVIRONAGE (ENVIRonmental influence ON early AGEing) birth cohort in Belgium.

Pairs lacking cord blood samples or missing data were excluded. Exposure to air pollution in the form of BC and PM2.5 was estimated using a model that integrated satellite land cover data and pollution data from monitoring stations.

Daily exposure values were averaged for the entire pregnancy and across trimesters. Cord blood samples were collected within 10 minutes of delivery, stored, and analyzed.

Cystatin C levels were measured in the samples using an accredited immune turbidimetry assay, where cystatin C binds to antibody-coated latex particles for quantification, providing insights into kidney function in newborns.

Statistical analysis involved the use of multiple linear regression analyses, distributed lag models, logistic regression analyses, and sensitivity analyses adjusting for various covariates, including age, education, smoking habits, alcohol consumption throughout pregnancy, and ethnicity.

Results and discussion

The average birth weight of newborns was 3,417.52 g, with 49.6% being girls, and the average gestational age was 39.2 weeks. Cord blood cystatin C levels averaged 2.16 mg/L. Mean exposure to BC and PM2.5 during pregnancy was found to be 1.18 μg/m³ and 12.65 μg/m³, respectively, remaining relatively constant across trimesters.

Significant associations were found between BC exposure during the entire pregnancy and elevated cord blood cystatin C levels, with a 0.5 μg/m³ increase correlating with a 0.04 mg/L rise (p<0.01). For PM2.5, a 5 μg/m³ increase was found to be associated with a 0.07 mg/L increase in cystatin C (p<0.01).

The first trimester showed associations with BC but not with PM2.5. Sensitivity analyses indicated that adjusting for additional covariates did not significantly alter effect estimates. Notably, the third trimester (beyond week 27) was identified as the most significant exposure window.

Higher exposures to PM2.5 and BC during the entire pregnancy and specifically in the third trimester increased the risk of higher cord blood cystatin C levels, with a 0.5 μg/m³ increase in BC linked to a 37% higher risk and a 5 μg/m³ increase in PM2.5 associated with an 80% higher risk.

The study is strengthened by its large, representative sample of well-characterized newborns and mothers with a prospective follow-up and high-resolution spatial air pollution model for fetal exposure estimation. However, the study lacks the use of additional markers to assess kidney function, such as creatinine.

Conclusion

In conclusion, the study shows that exposure to PM2.5 and BC during pregnancy, especially beyond week 27, is significantly linked to elevated cord blood cystatin C levels in newborns. This indicates the negative impact of particulate air pollution on kidney function since birth.

Therefore, monitoring early life exposure to particulate air pollution may be crucial for improving kidney health later in life. These findings warrant further research and aim to inform public health policy for improved outcomes in newborns.