Maternal exposure to endocrine disruptors affects semen quality

Wednesday, 28 April, 2021

Maternal exposure to endocrine disruptors affects semen quality

A growing number of studies show that the environmental factors and lifestyle habits of pregnant women play an important role in the health of their child. Now, scientists have established a link between poor semen quality in adult men and their mothers’ occupational exposure to endocrine disruptors during pregnancy.

Two years ago, researchers at the University of Geneva (UNIGE) showed that only 38% of Swiss men had semen parameters above the thresholds set by the World Health Organization (WHO) for fertile men. Collaborating with epidemiologists from France’s Research Institute for Environmental and Occupational Health (IRSET), the researchers sought to analyse the potential impact of endocrine disruptors on semen quality of men whose mothers were working at the early stages of their pregnancy.

Endocrine disrupters are chemical substances of natural or synthetic origin which can interfere with the endocrine system and cause adverse health effects in an organism or its progeny, according to the WHO. As noted by IRSET researcher Ronan Garlantézec, “Several animal studies have already shown that gestational exposure to certain endocrine disruptors can influence the development of the male reproductive system, as well as the sperm production and semen quality in adulthood.

“In view of the results obtained by Serge Nef’s team [at UNIGE] on the semen quality of young Swiss men, we were interested in studying the potential effect of exposure to endocrine disruptors during pregnancy as one out of many possible reasons behind the observed trends.”

The team led by Prof Nef evaluated semen quality of around 3000 conscripts, 1045 of which had their mother working during pregnancy. Prof Nef explained, “For each of them, a semen quality analysis was carried out to determine the semen volume, as well as the sperm concentration, motility and morphology.

“A detailed questionnaire was also sent to the parents before the semen analysis was carried out, covering in particular the maternal jobs exerted during the conscripts’ pregnancy period,” he added. This allowed for the analysis of semen parameters of men whose mothers were employed during their pregnancy.

“The maternal jobs were classified according to the International Classification of Occupations (ISCO-88 of the International Labour Office of the WHO),” said Luc Multigner, Research Director at the IRSET.

“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.” This has enabled epidemiologists to establish probabilities of exposure to one or more categories of products that may contain endocrine disruptors according to the mother’s occupation.

The results of the study, published in the journal Human Reproduction, show that young men exposed in utero to endocrine disruptors are twice as likely to have values below the reference values established by the WHO, both in terms of the semen volume (threshold at 2 mL) and the total number of spermatozoa per ejaculation (40 million). “In our study,” said Garlantézec, “the products most associated with these anomalies were pesticides, phthalates and heavy metals.”

The results of the study suggest an association between the mother’s occupational exposure to endocrine disruptors and a decrease in several semen parameters in their children during adulthood, though Prof Nef noted that these observations “do not determine the future fertility of young men, and only a follow-up over time will make it possible to assess the consequences”. An additional study is now planned in this same population to study the link between maternal occupational exposure to endocrine disruptors and changes in sexual hormones during adulthood.

Garlantézec said it would be “interesting to carry out a similar study in women, in order to evaluate whether the impact of endocrine disruptors is the same on the female reproductive system, although this is much more complex to carry out”. Multigner, meanwhile, said it appears necessary to inform pregnant women of the potential hazards of exposure to these substances, which could alter their children’s fertility.

The researchers noted that the data concerns mothers 25 years ago, and that since then the professions exerted by women have greatly evolved, as has the presence of endocrine disruptors in the products used.

“Hence the crucial preventive role of this study,” Prof Nef said.

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