When is your Fertility at its Peak?

When is your fertility at its peak? And how can you use this to maximize your chances of pregnancy? The “fertile window” is defined as the 5 days leading up to the day of ovulation and is the time frame when the viability of both eggs and sperm should be maximal. It is estimated that the fertilizable life of the human egg lasts up to 24 hours and that sperm can survive up to 5 days in the reproductive tract. The majority of sperm is believed to survive 48-72 hours, which is likely why studies support intercourse is most likely to result in pregnancy when it occurs within the 3 day interval ending on the day of ovulation. The likelihood of pregnancy has been shown to be greatest the day prior to ovulation and it starts to decline on the day of ovulation.

Given this data, pinpointing ovulation can help couples maximize their natural fertility. There are numerous methods out there for tracking ovulation including apps, basal body temperature (BBT) charts, ovulation predictor kits (OPKs), and tracking cervical mucus.

- Apps: Cellphone apps for tracking ovulation use a calendar method to predict your fertile days. They calculate on average when your fertile window should be by tracking average patterns in your cycles over many months. It is important to remember that these are just an estimate of your fertile window and that it is not looking at any biological parameters to suggest ovulation. The calendar method is also notoriously inaccurate for women with irregular menstrual cycles.

- Basal Body Temperature (BBT) Charts: Your body’s basal temperature increases minimally when you’re ovulating and can help confirm that ovulation has occurred. To track this, a woman must check their temperature each morning at the same time before getting out of bed and plot it on a chart. When you ovulate, the hormone progesterone causes your temperature to rise approximately 0.5 °F. BBT charting can confirm ovulation has happened but unfortunately the temperature spike only happens after ovulation has already occurred and when the fertile window has passed.

- Ovulation Predictor Kits (OPKS): OPKs can be purchased at most major drug stores and can help pinpoint the 2 best days to conceive. OPKs test your urine for a surge of a hormone called luteinizing hormone (LH), which normally occurs 24-36h prior to ovulation. Some kits also measure a hormone called estrogen, which increases as an egg is growing and can help predict “high fertility” days prior to the “peak” or “surge.” If using one of these kits, you want to test your first urine of the morning typically starting on cycle day 10. The most essential days to have intercourse are the day of the peak surge and the following day. Unfortunately, false positive test results occur in approximately 7% of cycles. These kits also do not work well in women with PCOS as these women often have high basal levels of LH and are prone to getting false positive “surges.”

- Cervical Mucus: Cervical mucus, which can be detected by vaginal secretions, correlates with the highest probability of conceiving when the mucus is slippery and clear. The volume of cervical mucus starts to increase over the 5 to 6 days preceding ovulation. This can be an inexpensive way to track the fertile window.

Frequency of intercourse can also help maximize natural fertility, especially in couples who are not tracking ovulation or the fertile window. The highest rates of conception per cycle have been found in couples with daily intercourse, but couples who have intercourse on alternative days have almost comparable conception rates. In general intercourse every 1-2 days is the optimal frequency to maximize chances of pregnancy. There is no evidence to support that position during intercourse affects the ability to conceive. While many couples believe that lying down for an interval of time post intercourse increases pregnancy rates, there is also no scientific data supporting this. For couples who use lubricant during intercourse it is important to use hydroxyethylcellulose based lubricants such as Pre-Seed, mineral oil, or canola oil. Many other lubricants, olive oil, and even saliva have been shown to decrease sperm motility and velocity.

Approximately 80% of couples will conceive in the first 6 months of attempting pregnancy. If you are trying to conceive and having difficulty it is important to seek care with a fertility specialist. Irregular menstrual cycles commonly occur in women who do not ovulate regularly and is a reason to seek care even earlier than 6 months.

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