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 have intercourse during this time become pregnant more quickly. Having sex during the fertile window also makes it easier for couples and their healthcare provider to decide whether not becoming pregnant is likely to be due to infertility rather than poor timing.
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. In fact, there is evidence that egg quality declines after 6–12 hours after ovulation, meaning the fertile window is shorter than commonly thought. In this regard, it is imperative to have sex prior to ovulation, so there are sperm available when the egg is released. 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 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 advised 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 declined in most women. It is the ‘ovulatory’ type mucus which enables the sperm to enter the uterus and thus reach the egg.
The best time to attempt conception is when a woman’s cervical mucus is wet, slippery and of egg white consistency, usually over a 2–3 day period. The last day of this fertile type mucus is usually the day of ovulation and should be followed by a temperature rise. The temperature rise confirms that ovulation has taken place. As sperm can live for up to 3–5 days it is best to try and have intercourse in the 2–3 days preceding and on the day of egg release (ovulation).
Urine-based Ovulation Predictor Kits test the urine for an increase (surge) in luteinising hormone (LH). This happens 1–2 days before ovulation. A small amount of LH is always present in your blood and urine. But in the days before ovulation, the amount increases several fold. The day before the LH surge until ovulation (12–24 hours after the start of the LH surge) is the most fertile time of your cycle. This is when you are most likely to conceive, so ensure that you do not wait until a positive LH test before having sex for conception.
When assisted reproductive technology such as IVF is used, one days’ abstinence is often advised - in this case the quality of sperm is more important than the quantity. Frequent ejaculation is better for the health of sperm while trying to conceive. Periods of abstinence longer than three days can be detrimental because of the accumulation of aged sperm. These are also the guidelines given when producing a sperm sample to be tested.
Men may choose to ‘empty out’ 2-3 days before conception attempts, to get rid of aged sperm, then let count build up for a couple of days before conception attempts. However, avoid this if it makes timing too complex and regimental.
Recording temperature is a retrospective tool to help understand your cycle, as it is important to have sperm already present when the egg is released – it will be too late once the temperature rise is detected.
Your temperature readings confirm whether you have ovulated. Your temperature rises because the ovaries switch from making estrogen to progesterone after ovulation. You will have relatively low temperatures from the time of your period until you ovulate. Ovulation will then cause a rise of about 0.2°C. The beginning of the rise in temperature signifies ovulation. Once you have ovulated, the temperatures remain high until there is a dip just before your next period. Temperatures must be taken under the tongue with a digital thermometer first thing in the morning before getting out of bed. It is also important to note that your temperature may fluctuate in response to other factors, such as infections.
Learn when - and where - you should seek help with your fertility
The nature of your cervical mucus tells you when you are approaching ovulation. Mucus is stimulated by the rising levels of estrogen made by the follicle growing in the ovary. The amount will increase as you get closer to ovulation. The texture can vary from none to pasty in the non-fertile phases, to stretchy or raw egg white consistency before and close to ovulation. Post ovulation the mucus generally changes back to the infertile type consistency. Sperm requires this ‘egg white’ type mucus to swim through in order to fertilise the egg. Recognising this mucus is therefore key to understanding your fertility.