For women who plan to get pregnant, knowing when ovulation will occur is critical. According to "Comprehensive Gynecology," the chance of getting pregnant peaks when intercourse occurs on the day of ovulation or up to 2 days before ovulation. Several signs can indicate when ovulation will occur, and using more than one indicator increases a woman's chances of correctly predicting the timing of ovulation.
The cervix, the narrow opening to the uterus, produces mucus throughout the menstrual cycle. As ovulation approaches, changes in the hormones produced by the ovaries affect the amount and consistency of cervical mucus. Just before ovulation, the cervical mucus becomes more abundant. It feels more watery and slippery, and a woman can stretch it to approximately an inch between her fingers.
Basal Body Temperature
A woman's basal body temperature increases when circulating levels of the hormone progesterone increase. The ovaries produce more progesterone after ovulation, causing body temperature to rise by a few tenths of a degree and stay elevated for three to four days. Charting daily fluctuations in basal body temperature over a few menstrual cycles can help a woman anticipate when she is likely to ovulate in a future cycle. For some women, a drop in basal body temperature occurs with ovulation, followed by an increase the next day.
Luteinizing Hormone Surge
The most reliable indicator of impending ovulation, levels of luteinizing hormone, or LH, can be measured with an over-the-counter kit. LH levels surge to prompt the ovarian follicle to burst and release an egg 12 to 24 hours later, according to "Comprehensive Gynecology." Ovulation kits measure the amount of LH in a urine sample, and a positive sample indicates LH levels high enough to cause ovulation the next day.
Some women can feel the ovarian follicle swell or burst to release an egg at ovulation, sensing it as a dull ache or twinge of pain on one side of the abdomen at about day 14 of a normal menstrual cycle. The pain, which usually lasts for a few hours, is called mittelschmerz, meaning "middle pain," and according to the Mayo Clinic, about 1 in 5 women will experience it at least occasionally. The sensation might be due to the pressure of the follicle against the surface of the ovary or to irritation of the lining of the abdomen from blood or fluid released when the follicle ruptures.
Some women might experience other signs and symptoms of impending ovulation. For some women, tender breasts and abdominal bloating signal that ovulation is about to occur. Other women might notice increased sensitivity to smells and tastes or have an increased sex drive just before ovulation. These signs are not present in all women, however, and could have multiple causes. They do not necessarily indicate ovulation, so they should be used only to bolster confidence in other, more reliable indicators.