Scientists have shown environmental pollutants can have adverse effects on pregnant women and their babies. But researchers are still uncertain how their exposure to air pollution, like exhaust fumes from passing cars, affects fetal development.
Car exhaust fumes release gasses and airborne particles termed traffic-related air pollution, or TRAPs for short. These include nitrogen dioxide (NO2), ozone (O3), and two types of tiny particles called PM2.5 and PM10. Scientists from the University of Murcia in Spain recently tested whether exposing a mother to TRAPs during her pregnancy would affect the number of immune cells in her newborn baby.
The scientists suggested if immune cell counts were lower in newborns affected by TRAPs, the mother’s inhalation of traffic exhaust could be impairing their immune system. Babies are more likely to experience infections, asthma, and bad allergies when their immune cell counts get too low.
Previous researchers examined how a pregnant mother’s exposure to NO2 and particulate matter affected immune cell counts in newborns. They found contradictory results, since some of the studies suggested certain immune cells decreased and others suggested the opposite.
These scientists set out to determine what TRAPs, if any, worsen immune cell counts in newborns. They also wanted to figure out when TRAP exposure could be most harmful during a pregnancy.
The team enrolled 738 pregnant women with similar backgrounds and health statuses in their study. The women were all aged 18-45, of Spanish Caucasian origin, lived in the Region of Murcia in Spain, and had no existing chronic diseases or pregnancy complications.
The researchers used an existing modeling program that analyzes weather data to track the concentrations of TRAPs in each woman’s neighborhood throughout her pregnancy. They compared the average TRAP concentrations during four specific time frames: trimester 1, or the first third of the pregnancy, trimester 2, trimester 3, and 15 days before birth.
When 390 of the babies were born, the scientists took blood samples from their umbilical cords. They counted immune cells in 190 of the blood samples. The immune cells they counted were natural killer (NK) cells, helper T (Th) cells, and regulatory T (Treg) cells. They used this data to look for correlations between the mother’s exposure to TRAPs at certain times of the pregnancy and the immune cell counts of the newborns.
The researchers found women living in areas with high NO2 and PM10 concentrations fifteen days before birth had babies with less NK and Treg cells. However, mothers exposed to high PM10 and PM2.5 concentrations during the first and third trimesters had babies with more Th cells.
From these results, the scientists concluded that fetal immune systems were more likely to be harmed by TRAP exposure during the first trimester and within 15 days of birth. The team reasoned TRAPs are harmful in the first trimester because immune cells are developed in fetuses at around week 4 in the pregnancy. They remained unsure why a similar effect occurred immediately before birth.
The scientists also suggested less NK cells could increase the baby’s risk of developing respiratory infections, since these cells are crucial for killing virus-infected cells and fighting diseases. They explained changes in Treg and Th cells could also affect an infant’s tolerance to allergens, since these specific immune cells are responsible for the body’s allergic response.
These findings show a pregnant woman’s exposure to air pollutants has the potential to negatively impact the immune system of her baby. The scientists suggested follow-up studies could investigate whether the negative impacts of TRAPs on immune cell counts would affect allergies or respiration in these children as they grow up.