Fertility NZ is a registered charity dedicated to providing information, support and advocacy to people experiencing fertility issues.

Timing of Sex

Intercourse timing and frequency relative to ovulation is possibly the most important factor affecting the chances of conception. It is also the element over which couples trying to conceive have the greatest degree of control.

Couples who are aware of their fertile time and focus intercourse during this time have been found to have much higher conception rates than couples who are unaware of their most fertile time .

Identifying the fertile window also allows couples and their healthcare provider to retrospectively ascertain if diagnostic investigations or interventions are needed, depending on whether intercourse has been timed optimally or not.

The ‘fertile window’ is determined by the lifespan of the sperm in the female reproductive tract and the life of the egg once it has been released at ovulation. Sperm live up to 3-5 days and the egg survives for 12-24 hours.  Based on studies the maximum fertile window has been determined to include the day of ovulation and the five days preceding ovulation. The most probable days for intercourse to result in pregnancy are 1 or 2 days before ovulation.

The currently available evidence suggests that methods that prospectively identify the window of fertility are likely to be more effective than calendar calculations or basal body temperatures, for optimal timing of intercourse. These include fertility charting of vaginal discharge and using commercially available fertility monitors.  However, caution is suggested when relying on urinary LH detection kits alone. The quality of cervical mucus falls rapidly as progesterone rises in response to the LH surge. Hence by the time the LH is detected by urinary ovulation kits, the cervical mucus quality may have already have declined in most women.