Semen quality linked to environmental factors during mother's pregnancy

Semen quality may be impacted in men whose mothers were exposed to certain chemicals whilst pregnant, a recent study has found.

The research, carried out by epidemiologists from the Research Institute for Environmental and Occupational Health (IRSET) in Rennes, France, in collaboration with researchers from the University of Geneva, Switzerland, analysed the semen of around 3000 Swiss males. Prior to the analysis being carried out, the subjects' mothers completed a detailed questionnaire relating to their jobs during pregnancy. Of the 3000 men, 1045 had mothers who worked during pregnancy.

'Maternal jobs were classified according to the International Classification of Occupations', Dr Luc Multigner, research director at IRSET explained. 'Exposure to products containing endocrine disruptors during pregnancy has been defined using a job-exposure matrix, which makes it possible to attribute the maternal exposure a probability score.'

The endocrine system consists of glands that make hormones. Endocrine disrupters are natural or synthetic chemicals that can interfere with the endocrine system and cause adverse health effects in an organism, or its offspring. This study discovered that, in total, 138 mothers were deemed to have been exposed to endocrine disruptors during pregnancy.

Published in Human Reproduction, the study showed sons of mothers exposed to endocrine disruptors during pregnancy, particularly pesticides, phthalates and heavy metals, were twice as likely to have semen volume, concentration and total number of sperm parameters below World Health Organisation reference values, compared to sons of unexposed mothers.

Previous animal studies have shown that gestational exposure to specific endocrine disruptors may affect development of the testes as well as semen quality in adulthood. Despite the results of this study suggesting this may also be the case in humans, researchers pointed out this does not determine the fertility of the men.

'Nevertheless, the results could explain, at least in part, the low semen quality of some young Swiss men', said Professor Serge Nef from the University of Geneva, who led the study.

Given the data is derived from pregnant women around 25 years ago, it is noted that that the number of women working in pregnancy and risk of exposure to endocrine disruptors may have evolved greatly during this time. An additional study of the same population, is also planned to analyse the link between endocrine disruptor exposure during pregnancy and changes in sexual hormones in adulthood.