Infertility: definition, causes and when to see a doctor

The medical definition

Infertility is defined as the absence of pregnancy after 12 months of regular intercourse without contraception. That is the threshold used by the World Health Organization and by the French health authority (HAS).

The definition published in 2023 by the American Society for Reproductive Medicine lowers the threshold to 6 months for women aged 35 and over, and extends the definition to single people and same-sex couples who need medical assistance to conceive.

This is a clinical marker, not a verdict: passing these thresholds means an assessment is warranted, not that pregnancy has become impossible.

How many people are affected

Figures vary with the source and the way they are measured. Santé publique France reports that roughly 1 couple in 8 consults for difficulty conceiving. An epidemiological study by Inserm, cited by the French health insurance service, points instead to 1 couple in 4 whose plans to have a child were affected by infertility.

The gap is not a contradiction: it reflects the difference between “consulted a professional” and “experienced difficulty”. Many of those affected never consult at all.

How the causes are distributed

According to the data reported by the French health insurance service and Inserm, the usual breakdown is as follows:

• about 25% of cases originate with the woman,
• about 25% originate with the man,
• about 25% are mixed, involving both partners,
• about 25% remain unexplained after assessment.

When to see a doctor

The marker is 12 months of unsuccessful attempts, reduced to 6 months from age 35. A general practitioner or a gynaecologist is the right first contact: the initial assessment covers both partners.

Consulting earlier is entirely reasonable when there is a known history — very irregular cycles, endometriosis, pelvic surgery, chemotherapy or an undescended testicle, for example.