Pollution causes restricted foetal growth

Traffic-related air pollution negatively affects foetal growth, according to the study published by researchers from the Centre for Research in Environmental Epidemiology (CREAL) in the journal Environmental Health Perspectives. The study specifically concludes that pollution causes the foetuses of pregnant women to weigh 81.6 grams less with respect to mean foetal growth between weeks 20 and 32 of pregnancy.

In fact, this research indicates that the lower foetal weight occurs in women who live close to a busy road and who are therefore exposed to higher NO2 or nitrogen dioxide levels.

The study indicates that for each increase of 10 ug/m3 (micrograms per m3) in the exposure to NO2 or nitrogen dioxide, which is a fairly common increase in big cities, the growth of the cranial perimeter is 6.24mm less than the mean growth between weeks 12 and 20 of pregnancy. On the other hand, a decrease of 6.37mm in the growth of the abdominal perimeter and a decrease of 2.16mm in the growth of the biparietal diameter (distance between one parietal eminence to the other) is observed with respect to the mean growth between weeks 20 and 32. These decrease measurements are compared against the mean growth of the study population. It should be noted that foetal weight is estimated based on the aforementioned measurements.

It should be taken into account that the mean concentration of NO2 in Sabadell over the course of the study period was 51 µg/m3, which is slightly lower than the concentration found in cities such as Barcelona or Madrid.

In addition, results indicate that exposure to ambient pollution in early pregnancy has a negative effect during mid-pregnancy. However, Dr. Inma Aguilera, coordinator of the study and researcher from the CREAL, states that “we cannot claim that pollution affects certain periods more than others, only that we have found an effect in a specific period, which is mid-pregnancy”.

The 562 women who participated in this research study, within the framework of the INMA (Environment and Childhood) project, reside in Sabadell (Barcelona) and data obtained from three prenatal ultrasounds were used for the analysis.

EFFECTS ON HEALTH

Impaired intrauterine growth is a response to an adverse prenatal environment and is associated with delayed neurodevelopment and growth problems during childhood, as well as with a higher risk of suffering cardiovascular diseases and metabolic syndrome in adulthood. In spite of this, Inma Aguilera, coordinator of the study and researcher from the CREAL, underscores that “for the time being” the detected negative effect of air pollution on foetal growth is “small”.

Dr. Aguilera points out that the impact on public health could be “relevant” given that, on the one hand, air pollution affects the entire population, and, on the other, foetal growth is an important indicator of perinatal health.

DEPENDING ON THE AREA OF RESIDENCE

This study also confirms the findings of certain prior studies that suggest that the area of residence influences the health of its inhabitants depending on whether it is close to busy traffic areas. In this respect, the CREAL researcher believes that “air pollution levels should be taken into account as a factor in urban planning when determining the location of certain facilities such as schools, daycares or hospitals”.

FIRST STUDY THAT OBSERVES THE FOETUS

While the majority of studies have assessed foetal growth indirectly by performing anthropometric measurements at birth (such as weight or height), this is the first study that employs ultrasounds to assess foetal growth directly, obtaining more accurate measurements.

Furthermore, it is the first study of these characteristics that has applied geographic analysis techniques to estimate individual exposure levels, therefore improving the assessment of exposure with respect to previous studies.

At present, the CREAL team is working on the joint analysis of four cohorts of the INMA project (Sabadell, Valencia, Asturias and Guipuzcoa) in order to determine whether the same results are obtained, as well as on the study of other perinatal effects associated with the exposure to ambient contamination (such as premature births or intrauterine mortality).

Reference article:
Prenatal exposure to traffic-related air pollution and ultrasound measures of fetal growth in the INMA-Sabadell cohort. Environmental Health Perspectives. 118:705-711.