For couples trying to conceive, it is very useful to know when is the optimal time to have sexual intercourse. The fertile period or ‘window’ seems to stretch for the 6 days leading up to ovulation and ends on the day of ovulation. Outside this window, a pregnancy is extremely unlikely. It has been estimated that the chances for pregnancy were 10% with intercourse 5 days before ovulation and 33% on the day of ovulation.
A woman who has regular menstruation within the limits of every 24 to 35 days has a 95% chance that she is ovulating. Ovulation in a regularly cycling woman can be estimated to occur 12-14 days before the day of the expected period. Such women should not need any further aid to detect ovulation. The same can be said for those who have slight pain or discomfort in mid-cycle (Mittleschmertz) indicating the day of ovulation.
The consistency of the cervical mucus changes in the days preceding ovulation, becoming copious and stretchable when examined between fingers. Some women will be able to assess the time of the fertile window using this method. Immediately following ovulation, the cervical mucus dries up.
A basal body temperature chart (BBT) has been a popular method to detect that ovulation is occurring. The principle is that following ovulation the secretion of progesterone causes a rise in body temperature of about 0.5 degrees C. Temperature measured immediately on waking across the month will show a ‘biphasic’ pattern with the temperature following ovulation being higher than in the first part of the cycle. The day before the temperature rise is usually denoted as the day of ovulation. Although this method may be useful in establishing the pattern of when ovulation is occurring, it has several drawbacks. It can be stressful, inaccurate and it does not provide a prospective indication of the day of ovulation.
Kits are available over the counter for measuring LH in the urine. LH rises precipitously on the day before ovulation and these kits will indicate when this happens. In a woman with regular cycles testing is recommended starting on day 9 of the cycle. As well as being expensive, they may also cause some stress.
Finally, a word of warning. Tension often arises when intercourse is timed by these methods. Abstinence until the time of ovulation can be detrimental to sperm function and probably the best advice is for couples to have intercourse every 2-3 days in the first part of the cycle and daily at the predicted time of ovulation.
Amit Shah, Anil Gudi & Prof Homburg