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. But how about the semen quality of young men? Researchers at
the University of Geneva (UNIGE), Switzerland, showed two years ago that
only 38% of Swiss men had semne parameters above the thresholds set by the
World Health Organisation (WHO) for fertile men. Epidemiologists from the
Institut de recherche en santé, environnement et travail (IRSET, Rennes,
France), in collaboration with the UNIGE team analyzed the potential impact
of endocrine disruptors on semen quality of men whose mothers were
working at the early stages of their pregnancy. Their results, published in
the journal Human Reproduction, show that men who have been exposed in utero
to products known to contain endocrine disruptors are twice more likely to
have semen volume and total sperm count per ejaculation below the reference
values set by the WHO.
Endocrine disrupters are chemical substances of natural or synthetic origin
which can interfere with the endocrine system and causes adverse health
effects in an organism, or its progeny, according to the World Health
Organization (WHO). “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,” explains Ronan Garlantézec, a researcher at
the IRSET, the Rennes University Hospital Centre (CHU) and University of
Rennes 1. “In view of the results obtained by Serge Nef’s team 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”, he continues.
The semen of more than 1000 conscripts analysed
The team of Serge Nef, professor at the Department of Genetic Medicine and
Development of the UNIGE Faculty of Medicine, has evaluated semen quality of
around 3000 conscripts, 1045 out of which had their mother working during
pregnancy. “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,” explains the Serge Nef. “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.”
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),” explains 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.
Endocrine disruptors associated with poorer sperm quality
The results of this study 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, the products most associated with these anomalies were
pesticides, phthalates and heavy metals”, notes Ronan Garlantézec.
“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.
Nevertheless, the results could explain, at least in part, the low semen
quality of some young Swiss men”, Serge Nef continues. An additional study
is already planned in this same population to study the link between
maternal occupational exposure to endocrine disruptors and changes in sexual
hormones during adulthood.
Preventing exposure to endocrine disruptors
The results of this 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. “It therefore appears
necessary to inform women planning to conceive and during their early stages
of pregnancy of the potential hazards of exposure to these substances, which
could alter their children’s fertility”, underlines Luc Multigner.
“Similarly, 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”, explains Ronan Garlantézec. Finally, the data concerns mothers
25 years ago. 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”, concludes Serge Nef.
Reference:
Istvan M, Rahban R, Dananche B, et al. Maternal occupational exposure to
endocrine-disrupting chemicals during pregnancy and semen parameters in
adulthood: results of a nationwide cross-sectional study among Swiss
conscripts. Human Reproduction. 2021;(deab034). doi:
10.1093/humrep/deab034