A study by the Institute of Global Health of Barcelona ( ISGlobal ) and recently published in the International Journal of Hygiene and Environmental Health analyzes hypertension disorders during pregnancy, which are one of the main causes of maternal and fetal mortality and morbidity.
Exposure to environmental chemicals may increase the risk of hypertension, but few studies have studied the impact of non-persistent chemicals – those that remain in the body only for a short period of time – particularly among pregnant women.
In this study, which is part of the HELIX project , 152 pregnant women were followed up in Barcelona (Spain), Grenoble (France) and Oslo (Norway). Three daily urine samples were collected during a week in two trimesters of pregnancy in order to evaluate their exposure to 21 substances: ten metabolites of phthalates, seven phenols including parabens or bisphenol A (BPA), and four metabolites of organophosphorus pesticides. Blood pressure was measured at the end of each week.
The results showed that “greater exposure to some phthalates, BPA and parabens was associated with a significant decrease in blood pressure, both systolic and diastolic ,and especially in the second trimester of pregnancy,” explains Charline Warembourg , researcher at ISGlobal and first author of the publication. No association was found with exposure to pesticides.
“Our findings do not support the hypothesis suggested by previous studies of a hypertensive effect of phthalates, phenols or pesticides during pregnancy,” concludes Maribel Casas , ISGlobal researcher and coordinator of the study. “This apparent contradiction with research in non-pregnant populations may reflect the physiological changes that occur during pregnancy and that modify blood pressure,” she adds.
Thus, non-persistent chemicals could expand the effect of lowering blood pressure, which is frequently observed in the first two trimesters of pregnancy. Another possible explanation is that “the study did not cover the third trimester of pregnancy, period when the risk of the onset of hypertensive disorders begins,” says Warembourg.
A potential mechanism that could explain how these chemicals affect blood pressure is endocrine disruption. Once the chemical compounds enter our body through diet, skin or air, they travel through the bloodstream and can mimic the action of hormones. For example, BPA has estrogenic properties and estrogens have a protective effect on arterial stiffness.