Infertility: endocrine disruptors, tobacco, poor sperm quality… what are the risk factors ?

Infertilité : quels sont les facteurs de risque ?

With Emmanuel Macron's press conference and the launch of a major plan against infertility, it has become a major public health issue. Often multifactorial, how can we explain, by excluding medical causes, the reproductive problems encountered by many people around the world ?

President Macron announced during a press conference on January 16, a major plan against infertility. The same day, INSEE announced an unprecedented drop in births in France, the lowest since 1945.

One of the main causes: Prof. Samir Hamamah, head of the reproductive biology department at Montpellier University Hospital, 3.3 million people are affected in France among adults aged 20 to 49. As a reminder, "we speak of infertility of a couple when a pregnancy is not obtained after 12 to 24 months of complete sexual intercourse, regular (two to three times a week) and without contraception", note Ameli.fr.

Later age of motherhood

"In 2019, French women had their first child at the age of 29 on average. As fertility gradually declines from the age of 30, so-called ‘late’ mechanically increase the risk of infertility, notes the report of Professor Hamamah. Thus, ovarian failure is the leading cause of infertility in women after the age of 35.

According to an INED study cited in the report, "if the risk of infertility actually affects around 1 couple in 4 to 30 years , it rises to 1 couple in three at 35 years old (34%) and more than one couple in 2 at 40 years old (56%).

Many couples then turn to medically assisted procreation (AMP), but the chances of success greatly diminish with age. "The ignorance of many couples about the reality of the decline in their fertility with age, combined with excessive confidence in the performance of medically assisted procreation techniques, results in an increasingly late request for medical support, thus limiting success rates, adds the report.

Less and less sperm

Gradually declining sperm quality is yet another factor. According to a Public Health France study published in 2018, sperm concentration had decreased by 32.2% between 1989 and 2005.

How to explain such a drop in sperm concentration ? Several studies implicate exposure to glyphosates.

Dr. Fleur Delva, coordinator of the Artemis platform at Bordeaux University Hospital, receives consultations with patients suffering from fertility disorders and investigates possible environmental, professional or extra-professional exposures. It thus points to exposure to heat which has an effect on spermatogenesis, as well as ionizing radiation (medical sector, nuclear industry, industrial sector…) in particular.

We must also look at lifestyles and in particular sedentary lifestyle. "If the effect on spermatogenesis is not proven, we consider it plausible that prolonged sitting has negative effects on male fertility. We advise them to take breaks and get up every two hours, indicates the epidemiologist.

Endocrine disruptors

Endocrine disruptors (ED) are present in our daily environment. They are accused of disrupting the endocrine system, made up of glands which secrete hormones involved in numerous functions, including reproduction. "An endocrine disruptor (ED) means a substance or mixture that alters the functions of the endocrine system and thereby induces harmful effects in an intact organism, in its offspring or within (sub)-populations", according to the WHO definition in 2002.

According to the report of Professor Hamamah, "endocrine disruptors interfere with the processes that regulate development, metabolism and reproduction and produce functional effects that are manifest very long after exposure. They generally have a broad spectrum of action. They can act simultaneously on several organs linked to gonadal development.

However, science struggles to quantify the effects of EDs on health because they disappear very quickly from the bloodstream. Difficult in these conditions to establish a strict link of cause and effect.

Reprotoxic substances

With her team, Fleur Delva has identified all reprotoxic substances, based on the work of scientific teams and official lists, to which populations may be exposed. "We have identified eight families which include substances potentially harmful to fertility (metals, phthalates, perfluorinated chemicals, pesticides, solvents…)& quot;, she explains. In total, his team identified 185 substances classified as proven or presumed reproductive risk factors and 750 suspected substances.

The population is widely saturated with many of these substances according to the biomonitoring component of the Esteban study, from Public Health France. The results show widespread impregnation of human blood and body fluids for six families of pollutants: bisphenols, phthalates, parabens, glycol ethers, brominated flame retardants and perfluorinated compounds.

Preventable risk factors: tobacco and cannabis

The deleterious effect of tobacco on fertility has been proven. "< /strong>Smoking reduces the fertility of men and women (risk of infertility multiplied by 2 in both sexes). It extends the time to conception by approximately 4 to 6 months, potentiates the negative effect of age, increases the risk of first trimester miscarriages and ectopic pregnancies. The increase in risk is dose dependent, explains Professor Hamamah's report.