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A Guide to Fertility

When should you start trying to get pregnant?

Because the fertility of women declines, many women who want children want to know at what age they should try to get pregnant to have a good chance of having the family they want.

Maximum female age at which women should start trying to get pregnant for 1,2, or 3 children and for a 50%, 75% and 90% chance of reaching the desired family size with and without using fertility treatment

Habbema, J. D. F., Eijkemans, M. J. C., Leridon, H., & te Velde, E. R. (2015). Realizing a desired family size: when should couples start? Human Reproduction, 30, 2215-2221. By permission of Oxford University Press.

Graphic 4 shows a chart of when a woman would need to start trying to get pregnant to have the number of children she wanted. To use the chart you need to know:

  1. The size of family you would like (e.g. 1, 2, or 3 children)
  2. Whether you would be willing to use fertility treatments (e.g. IVF) if you or your partner could not become pregnant naturally
  3.  Your desired certainty that you will achieve the family size you want (e.g. 50%, 75%, or 90% sure)

For example, the green numbers show that if a woman wanted to be 90% certain that she would have at least 3 children without ever using fertility treatment, then she would need to start trying for a family at 23. But, she could start aged 36, if she was willing to use fertility treatment and have a lower certainty (50%) of having 3 children (see blue numbers). Women (and their partners) can use this chart to decide when to start trying to get pregnant. If you know you have fertility problems that can be overcome with fertility treatment then look at the ages with fertility treatment (with IVF). Such a chart does not yet exist for men.

More Information


This guide gives you information about fertility and infertility. To help understand this information we’ve included an explanation of the main medical terms used.

  • eggs and sperm

    Cells that are produced by the ovary (eggs, oocytes, ova) and testicles (sperm) and that combine after sex to produce a pregnancy. Women produce eggs and men produce sperm. A healthy sperm is motile, which means it has the ability to move. This movement is what makes it possible for sperm to reach the egg.

  • ejaculation

    Semen is the fluid produced by the male sexual organs to protect and carry sperm. The process of discharging this fluid from the penis is called ejaculation.

  • insemination

    Treatment that involves directly inserting sperm into a woman’s womb.

  • menopause

    The menopause is the time when menstrual periods stop permanently, and women are no longer able to have children. For most women this happens at about 51 years. The age a woman will reach menopause generally be similar to the age at which her mother reached menopause.

  • menstrual cycle

    The monthly changes that occur in the female reproductive system (specifically the uterus and ovaries) which make pregnancy possible. The length of the menstrual cycle is calculated as the time from the first day of a woman’s period (bleeding) to the day before her next period or bleeding. The average time between two periods for women is about 28 days but in teenagers it could be longer (up to 45 days) and sometimes 2 to 3 months, becoming shorter as the teenager gets older. There are events that occur during the menstrual cycle which are repeated each month. These are: development of the egg (phase 1), release of the egg from one of the ovaries (phase 2), preparation of the uterus for a pregnancy (phase 3), and menstruation or bleeding (phase 4). The next period then happens if there is no pregnancy. Young women should have regular periods within 3 years of the rst period occurring. Women could have some spotting in early pregnancy.

  • ovaries

    The two oval-shaped organs located in the lower abdomen (right and left side) that produce the female eggs.

  • ovulation

    Is the release of the oocyte (mature egg, sometimes called ovum) from the ovaries, ready for fertilization. Ovulation occurs about two weeks before the next period is due, for example around day 14 of a 28-day cycle or day 21 of a 35-day cycle. The actual day of release could differ between cycles and between women, and is a affected by many factors (e.g. lifestyle).

  • testicles also called testes or balls

    Oval-shaped organs that sit in a sac that hangs behind the penis. A main job of the testicles is to make and store sperm.

‘A Guide to Fertility’ was developed and evaluated by Prof J Boivin, Cardiff University.