Definition of infertility and when to start assessment
Infertility is failure to conceive (become pregnant) after 12 months of regular sex without contraception (which a couple use when not trying to conceive), a time-based label.
Remember
Infertility means 12 months of regular sex without contraception and no pregnancy, and both partners are then assessed. A woman aged 36 or over, or a suspected or known cause, brings assessment forward but does not change the definition.
Infertility is a time-based label and not a diagnosis of cause. A couple are called infertile when they have not conceived after 12 months of regular sex without contraception. Regular means sex about every 2 to 3 days, and months of sex while using contraception do not count towards the year.
The year is chosen because more than 8 in 10 couples where the woman is under 40 conceive naturally within a year, and about half of those who have not conceived in the first year do so in the second. Infertility is therefore a label for delay, not permanent childlessness.
It affects about 1 in 7 couples in the UK. About 30% of cases are mainly female factor (the problem lies mainly with the woman), 30% mainly male factor, 25% combined factors and 15% unexplained after a full work-up (both partners have been assessed and investigated). Because a problem can lie with the woman, the man or both, both partners are assessed together.
The definition does not decide when to seek help for everyone. Initial assessment is offered whenever people are concerned about delayed conception, and when there is no suspected or known cause, both partners are offered further assessment and investigation after one year. Specialist referral is offered at presentation (the first visit) if the woman is aged 36 or over, or if either partner has a suspected or known cause or risk factor. Female age is the most powerful single factor in fertility. Fecundity (the chance of conceiving in each cycle) falls steeply from the late 30s and very steeply after 40, as the number of eggs left (the ovarian reserve) falls and more of the remaining eggs have the wrong number of chromosomes (aneuploidy). Age changes when assessment starts, not what infertility means.
Key facts
- Definition
- no pregnancy after 12 months of regular sex without contraception, at any age.
- Regular
- sex about every 2 to 3 days.
- Why a year
- more than 8 in 10 couples where the woman is under 40 conceive naturally within a year.
- How common
- about 1 in 7 UK couples are affected.
- Causes
- male, female and combined factors are roughly equal, with around 15% unexplained.
- Earlier help
- specialist referral is offered at presentation if the woman is aged 36 or over or there is a suspected or known cause.
- Age effect
- age changes the timing of assessment, not the definition.
Exam traps
- Six months is not the UK definition: it stays at 12 months, and a woman aged 36 or over is referred earlier, which changes when to seek help and not the definition itself.
- Months of sex while using contraception do not count towards the 12, because a couple using contraception are not trying to conceive, so failure to become pregnant tells us nothing about fertility.
- Losing a pregnancy that has already been conceived is not infertility, because infertility is failing to conceive in the first place.
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