Timing of sex fact fileDownload the PDF (93 KB)
Timing and fertility – a fact file
Knowledge about the ‘fertile window’ is low among Australians of reproductive age
- Two thirds of Australians have inadequate knowledge about the time in the menstrual cycle when a woman is most likely to conceive.
- Many women are unaware of when they ovulate.
- Accurately-‐timed intercourse can reduce time-‐to-‐pregnancy and help avoid unnecessary IVF treatment.
- Recommending sexual intercourse every 2 to 3 days can help those who are not aware of the ‘fertile window’ optimize their chance of conceiving.
What is the ‘fertile window’?
- Conception is only possible from about 5 days before ovulation through to the day of ovulation. These six days is the ‘fertile window’ in a woman’s cycle and reflect the lifespan of sperm (5 days) and the lifespan of the ovum (24 hours).
- The ‘fertile window’ depends on the length of a woman’s cycle. The time from ovulation to the next period is about 14 days, irrespective of cycle length. The time before ovulation varies between women.
- The likelihood of conceiving is dramatically increased if intercourse occurs in the three days leading up to and including ovulation.
When to have sex?
- In a 28-‐day cycle, ovulation typically occurs around day 14 and the chance of conceiving is greatest between days 11 and 14.
- In longer cycles, say 35 days between periods, ovulation happens around day 21 and days 18-‐21 are the most fertile days. In a 24-‐day cycle ovulation happens around day 10 and the most fertile days are days 7 to 10.
- If a woman has sex six or more days before she ovulates, the chance she will get pregnant is virtually zero.
- If she has sex five days before she ovulates, her probability of pregnancy is about 5%. Her probability of pregnancy rises steadily until the two days before ovulation.
- If she has sex on either of these two days, she has a 25-‐30% chance of becoming pregnant.
- After this, the probability of pregnancy declines rapidly and by 12-‐24 hours after she ovulates, a woman is no longer able to get pregnant during that cycle.
Be aware of physical changes too
- A few days before ovulation the vaginal mucus changes and becomes clear and slippery; the consistency of egg white. Mucus changes provide an early and useful cue that ovulation is approaching. Fertility awareness, the ability to recognise the physical changes that occur before ovulation, can help couples achieve pregnancy.