You are most likely to conceive if you have sex on the day you ovulate than on any other day during your menstrual cycle. Careful monitoring of ovulation and timing of intercourse is essential whether you want to get pregnant or are trying to avoid it.
Ovulation and the Fertile Days
When you have sex on the day you ovulate, you have a new egg and fresh sperm, making this the most fertile day of your menstrual cycle. Chances of pregnancy during ovulation are high. The second most fertile day is the day before ovulation.
According to a landmark study reported in 1995 in the New England Journal of Medicine, most women have a total of six fertile days in a normal menstrual cycle, including the day of ovulation. This means if you have intercourse on any of the five days leading up to the day of ovulation, you can still get pregnant even if you avoid sex on the day you ovulate.
What Determines the Fertile Days
The lifespan and survival of the egg and sperm are the factors that determine your best days of fertility (or fertile window) in the first half of your cycle. You conceive when there is viable egg and sperm available.
Egg and Sperm Survival and Fertilization
A 2014 review by the Global Library of Women's Medicine (GLOWN) notes the egg survives for only about 24 hours after you ovulate. Therefore, intercourse within that 24-hour window gives you the best chance of fertilizing a viable egg.
Based on the review, sperm, however, can survive in your reproductive tract for days. Sperm maintains its best fertilizing function for 72 hours on the average but can be still viable up to five days after intercourse. So, if you have sex on any one of your five other fertile days, you may still get pregnant on the day you ovulate, even if you avoid intercourse that day.
The Chance of Conception
If you time having unprotected sex during ovulation, your average chance of conceiving within three cycles ranges from 20 to 37 percent, the American Society of Reproductive Medicine (ASRM) states. The average chance of conception from having intercourse on the day of ovulation was about 33 percent in the NEJM study cited above.
If you have irregular cycles, you might have more difficulty pinpointing ovulation and therefore, your chance of conceiving each cycle might be lower than average within three cycles.
Tracking Ovulation for Conception
You can track signs of fertility to try to predict your day of ovulation to increase your chance of conception. ASRM recommends having intercourse every one to two days during the six-day fertile window that ends on the day on which you think you ovulate.
In reality, the methods to determine ovulation are not precise. Therefore, if you are trying to get pregnant, have intercourse an additional two days after your estimated day of ovulation.
Using the facts about ovulation and the most fertile days of the cycle and tracking your fertility signs can help you know when to avoid intercourse or use protection during your cycle to avoid getting pregnant.
If you have sex while ovulating or on your other potentially fertile days, you can reduce your chance of a pregnancy by using contraception, such as a condom, during intercourse. If do not use any contraception and have intercourse on or around the day you ovulate, getting emergency contraception, such as the morning after pill or the copper IUD, can help reduce your chances of pregnancy. These methods are effective if used up to 72 hours after intercourse.
Understand Your Fertility
Understanding your fertility on the day of ovulation and the five days preceding can help you increase your chance of conception if you are trying to get pregnant. This information is also useful if, instead, you are trying to avoid it.