Facts about infertility

February 2017

Infertility affects 80 million people in the world.

The National Institute for Health and Clinical Excellence (NICE) has defined infertility as "failing to get pregnant after two years of regular unprotected sex".

Difficulties in conceiving a child can cause much distress for many couples.

Facts and definitions


1 in 6 or 7 couples have problems with fertility in the UK:

Approximately 500,000 couples consult doctors each year for fertility problems.

Infertility is the one of the most common reasons for women aged 20-45 years to consult their doctor, second only pregnancy.
  • Primary infertility is when a woman has not managed to become pregnant before at all
  • Secondary infertility means that a woman has had an unsuccessful pregnancy in the past


The increase in infertility figures observed recently is mainly caused by women planning or becoming pregnant for the first time at a later age.

The average age of a first pregnancy for a woman in the UK is now 30 years old.
  • 40% of infertility is due to female causes and men are responsible for about 30%..
  • Infertility is unexplained in 10 to 15% of couples.

Average times to conception

  • At the age of 25, a couple has approximately a 25% chance to conceive at each cycle.
  • Most couple succeed in getting pregnant after 6 to 12 months.
  • According to the HFEA, out of 100 couples trying to conceive naturally with regular sexual intercourse:
    • 20 will conceive within one month
    • 70 will conceive within six months
    • 85 will conceive within a year
    • 90 will conceive within 18 months
    • 95 will conceive within two years

Maternal age


Female fertility reduces with age.

95% of women aged 35 will conceive after 3 years of regular unprotected sex (2 to 3 times a week). This falls to 77% for women aged 38.

Therefore, the earlier a woman tries to conceive, the more successful she will be.

Paternal age


The impact of age upon male fertility is not clear, but is thought to decline with advancing age.

How does conception occur?

  • A woman's cycle starts on the first day of her period and finishes on the last day before her next period starts.
  • Ovulation is the release of an egg and this usually happen in the middle of the cycle - for example, day 14 of a 28 day cycle.
  • When the egg is released, it travels down the fallopian tube where it can be fertilised by a sperm.
  • During sexual intercourse, the testicles produce millions of sperm which try to travel from the vagina into the womb. A small proportion of them cross the neck of the womb and then swim towards the tubes.
  • Fertilisation or conception occurs when a single sperm penetrates the egg.
  • This egg multiplies and divides to become an embryo which travels to the womb and attaches to the lining enabling it to grow further eventually into a foetus.

Sex hormones


Sex hormones play a central role in the menstrual cycle and fertility as they enable ovulation.

If you are having problems conceiving, your GP may organise you to have blood tests to check these hormones.

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