The increase in luteinizing hormone (LH) triggers ovulation. Ovulation is an event that occurs when a mature egg is released from your ovarian follicle to the nearest fallopian tube. Fertilization, the union of an egg and sperm, occurs in the fallopian tube. The egg, fertilized or not, then travels into the uterus.

At ovulation, in addition to estrogen, progesterone is now produced. These two hormones combined stimulate the dramatic changes in your endometrium that are necessary to allow a pregnancy to implant and grow. If you have regular 28-day cycles, ovulation usually occurs on day 14. However, most women have different cycle lengths. In general, ovulation occurs 11 to 16 days before your upcoming period.

Ovulation occurs when one of the ovaries releases a mature egg. The egg travels out of the ovary, into the nearest fallopian tube and into your uterus. As the egg moves down the fallopian tube, which takes several days, the lining of the uterus continues to grow thicker and thicker.