Ovulation is a phase in the menstrual cycle when your ovary releases an egg (ovum). Once an egg leaves your ovary, it travels down your fallopian tube where it waits to be fertilized by sperm. On average, it happens on day 14 of a 28-day menstrual cycle.
Ovulation and your menstrual cycle
The process of ovulation begins when your hypothalamus (a part of your brain) releases gonadotropin-releasing hormone (GnRH). GnRH causes your pituitary gland (a gland in your brain) to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
Between days six and 14 of your menstrual cycle, FSH causes follicles (small sacs of fluid in your ovaries that contain a developing egg) in one ovary to begin to mature. During days 10 to 14 of the cycle, only one of the developing follicles forms a fully mature egg. Around day 14 in the menstrual cycle, a sudden surge in LH causes the ovary to release this egg. This is ovulation. After ovulation, the hormone progesterone rises which helps prepare your uterus for pregnancy.
Ovulation, conception and pregnancy
Once ovulation occurs, your egg travels through your fallopian tube. It’s in your fallopian tube that your egg meets sperm for fertilization. If conception occurs (sperm fertilizes your egg), the fertilized egg travels down to your uterus. After about a week, the fertilized egg (now a blastocyst) attaches to the lining of your uterus. This is called implantation. Release of the hormones estrogen and progesterone causes the endometrium to thicken, which provides the nutrients the blastocyst needs to grow and eventually develop into a baby. As cells continue to divide — some developing into the fetus, others forming the placenta — hormones signal your body that a baby is growing inside your uterus. This also signals your uterus to keep its lining, which prevents you from getting your period. Not getting a period is usually the first sign you’re pregnant.