Exposure to more green spaces during pregnancy positively impacts infant birth weight

Key takeaways:

• Residence near green areas while pregnant positively impacted birth weight.
• This finding could help decrease the risk for lung function impairment that comes with low birth weight.

Pregnant women who lived near forests and parks had reduced odds for having low-birth weight babies, which may impact infant lung health, according to a presentation at the European Respiratory Society International Congress.

“Our results suggest that pregnant women exposed to air pollution, even at relatively low levels, give birth to smaller babies,” Robin Mzati Sinsamala, a PhD candidate and researcher in the department of global public health and primary care at the University of Bergen, Norway, said in a press release. “They also suggest that living in a greener area could help counteract this effect. It could be that green areas tend to have lower traffic or that plants help to clear the air of pollution, or green areas may mean it’s easier for pregnant women to be physically active.”

Using data from the Respiratory Health in Northern Europe (RHINE) study, Sinsamala and colleagues assessed 2,742 mothers and 5,434 children to determine how maternal air pollutant and greenness exposure are each linked to birth weight and preterm birth through linear and logistic regression models.

Researchers found each mother’s exposure levels to nitrogen dioxide (NO₂), ozone, black carbon (BC), fine particulate matter of 2.5 µm or less (PM_2.5) and fine particulate matter of 10 µm or less (PM₁₀) using their home address while pregnant.

Further, the Normalized Difference Vegetation Index (NDVI), which captures the density of vegetation (forests, farmlands and parks) in areas, allowed researchers to estimate greenness exposure.

Of the total cohort, the median NDVI using a buffer of 300 m was 0.3 (interquartile range [IQR], 0.2-0.4).

Among all the studied pollutants, researchers observed the highest median exposure levels with ozone at 49.5 µg/m³ (IQR, 45.2-54), followed by PM₁₀ at 16.4 µg/m³ (IQR, 11.1-21.3), NO₂ at 15.8 µg/m³ (IQR, 8.9-21.6), PM_2.5 at 9.5 µg/m³ (IQR, 7.1-13) and BC at 0.6 µg/m³ (0.4-0.8).

With the exception of ozone, elevated air pollutant levels resulted in decreases in birth weight by 56 g (PM_2.5), 46 g (PM₁₀) and 48 g (NO₂ and BC), according to the press release.

After adjusting for several variables (center, maternal age, education, smoking, body silhouette and comorbidity), researchers found that a higher score on the NDVI 300 m factored into better baby birth weight outcomes. With more exposure to green areas, based on an IQR increase in the NDVI 300 m, birth weight increased by 29 g (95% CI, 13-44), the odds for high birth weight (> 4,000 g) went up by 14% (OR = 1.14; 95% CI, 1.02-1.26) and the odds for low birth weight (< 2,500 g) went down by 23% (OR = 0.77; 95% CI, 0.64-0.94).

Notably, even with adjustment for air pollutants’ exposures and use of NDVI buffers of 100 m and 500 m, the positive association between greenness exposure and birth weight remained.

Unlike birth weight, researchers did not find a link between preterm birth and greenness exposure.

“The time when babies are growing in the womb is critical for lung development,” Sinsamala said in the release. “We know that babies with lower birthweight are susceptible to chest infections, and this can lead on to problems like asthma and COPD later on.”

Reference:

• Mums exposed to air pollution give birth to smaller babies, but living in a greener area may mitigate the risks. https://www.eurekalert.org/news-releases/1000633. Published Sept. 7, 2023. Accessed Sept. 8, 2023.