Finding the Fertile Window – Any Method Will Work

By: Dr. Jessica McLaughlin

I am commonly asked how to monitor ovulation and how to find that fertile window. The “fertile window” is classically defined as the 6-day interval ending with the day of ovulation. Intercourse is most likely to lead to pregnancy when it occurs within the 3 days interval ending on the day of ovulation. The probably of achieving a pregnancy in that cycle increases with the frequency of intercourse during that fertile window.

There are many fertility indicators used to help identify the fertile window. Accurately predicting ovulation can be challenging with any available method. Different methods include examining changes in cervical mucous, monitoring basal body temperature, urine LH kits or ovulation predictor kits (OPKs), or charting menstrual cycles.

A recent study looked at the frequency of use of selected fertility awareness indicators and assessed their influence on pregnancy. A total of 5,688 women that had been trying on average for 2 months at baseline were analyzed and followed for 1 year. 75% of these women at baseline were using one or more fertility indicators. These included charting menstrual cycles (71%), measuring basal body temperature (21%), monitoring cervical fluid (39%), using LH kits (32%) or feeling for changes in the position of the cervix (12%). Women using some sort of fertility indicator had higher subsequent fecundability (meaning shorter time to pregnancy) than those that were not using any sort of fertility indicator. (Stanford, JB et al. Fert and Ster. 2019)

When the different types of indicators were examined individually, interestingly there were no differences in outcomes noted. This means that utilizing a no-cost method such as charting cycles or counting days is just as effective as more costly methods such as urine LH kits. It can easily cost $30-$50 a cycle at the local drug store for OPKs. Patients should also know approximately 10% of patients can have false positives with OPKs. Devices like OPKs used to predict the time of ovulation may be useful for couples who have infrequent intercourse. If patients do want to use OPKs, we recommend testing only once a day, with the second void in the morning.

It is clear from the study that use of fertility indicators is very common among those planning for pregnancy. The most common is charting cycles and many women are using multiple fertility indicators. This study shows that really any method for tracking fertilization will work and intercourse every 1 to 2 days during the fertile window can help maximize pregnancy rates.

If you have questions about ovulation or tracking your fertility, you can make an appointment to see one of our experienced physicians by calling 843-883-5800.