What is Ovulation, and How Does It Happen?
Ovulation happens when the ovaries release a mature egg, and it travels down the fallopian tube to await fertilization. Women are most likely to get pregnant on the day of ovulation and the five days before it. Therefore, it’s vital to understand this important menstrual cycle phase when trying to conceive. Here’s everything you need to know about ovulation.
What is Ovulation?
Each month, your body prepares for the possibility that you may become pregnant by triggering a hormone called follicle-stimulating hormone (FSH). This FSH hormone causes eggs to mature in individual follicles located in your ovaries. Each follicle produces another hormone called estrogen, which must reach a certain level for ovulation to occur.
When enough estrogen has been produced—usually anywhere from 12 to 18 days after your cycle begins—this triggers the release of a third hormone called luteinizing hormone (LH), says Staci Pollack, M.D., an OB-GYN for the Division of Reproductive Endocrinology & Infertility at Montefiore Health System. LH is what's detected in your urine if you track ovulation with a drugstore predictor kit. It surges 24-36 hours before ovulation and causes your egg to burst from the most mature follicle. The release of the egg is known as ovulation.
After being released from the ovary, the mature egg will enter the fallopian tube. It'll stay in the reproductive tract for about 12-24 hours, during which time sperm needs to be present for fertilization to take place.
What Happens After Ovulation?
After ovulation, the newly empty follicle—now called the corpus luteum—begins to produce yet another hormone, progesterone, which prevents your body from releasing more eggs for the duration of the cycle.
If the egg is not fertilized: It will disintegrate after about 12 to 24 hours and either get reabsorbed into the body, or pass out with the menstrual flow. The corpus luteum functions for about another 12 to 16 days, after which progesterone levels drop, you get your period, and the cycle begins all over again.
If the egg is fertilized: It will spend the next week or so traveling through the fallopian tubes to the uterus, where it will burrow into the uterine lining and begin the amazing process of developing into a baby. Your progesterone levels stay elevated, which is why your period goes away when you're expecting.
When Am I Most Fertile?
A woman’s chances of conceiving are highest on the day of ovulation, as well as the 24 hours beforehand, says Jingwen Hou, M.D., Ph.D., an OB-GYN specializing in reproductive endocrinology and infertility at Kaiser Permanente in Hawaii. However, sperm can survive for up to five days in the reproductive tract, says Dr. Hou, so a woman may conceive by having unprotected sex up to five days prior to ovulation.
When Does Ovulation Happen?
Just like menstrual cycles vary between women, the time of ovulation is also unpredictable. However, as a rule of thumb, ovulation is likely to happen 14 days before the start of your next period, says Sharifa Menon, M.D., F.A.C.O.G, an OB-GYN at Westchester Medical Center, the flagship of the Westchester Medical Center Health Network (WMCHealth).
In general, you simply need to take your cycle length and subtract 14 days. If you have a regular 28-day cycle, for example, you’ll likely ovulate 14 days into your cycle (day one is the first day of your last menstrual period). If your cycle is 30 days long, though, ovulation will probably occur around day 16.
Women with irregular cycles can expect ovulation anywhere from 11 to 21 days into their cycle. Ovulation calculators and fertility kits might help clear the confusion, or you can visit the doctor for advanced fertility testing. He may sample progesterone levels in the blood or monitor ovulation with a pelvic ultrasound, says Dr. Hou.
Can I Tell When I’m Ovulating?
About a fifth of all women experience lower abdominal pain, known as mittelschmerz, when ovulation occurs. “It can be dull, crampy, or even sharp in nature, and can last from minutes to two days,” says Rashmi Kudesia, M.D., an OB-GYN and reproductive endocrinology and infertility specialist at Houston Methodist and Houston IVF. Breast tenderness or discomfort is also common. Most women have a vaginal discharge that is clear and somewhat elastic (try stretching it between two fingers) in the days leading up to ovulation.
If you want to track ovulation, you have a few different options. For example, ovulation predictor kits (OPKs) can help detect the LH surge that precedes the release of the egg, while charting your basal body temperature (BBT) can be used as a marker for ovulation.