Ovulation is a physiologic process defined by the rupture and release of a mature egg or dominant follicle from the female ovary into the fallopian tube, where it has the potential to be fertilized by a male sperm cell. The ovulation process involves various hormones that regulate the hypothalamic-pituitary-ovarian axis function. For example, the hypothalamus secretes GnRH in a pulsatile manner, which signals the release of FSH and LH from the anterior pituitary. These hormones act on granulosa and theca cells in the ovary to stimulate the maturation of the dominant follicle and, in turn, initiate ovulation.
Ovulation is a critical part of the menstrual cycle, which typically occurs around day 14 of a regular 28-day cycle. However, the length of menstrual cycles varies from woman to woman. This knowledge is essential for couples who plan to conceive. For couples pursuing pregnancy, the highest probability of pregnancy tends to occur one to two days before ovulation.
There are different methods to detect the timing of ovulation. Aside from menstrual cycle charting, also known as the calendar method, test kits to detect whether one is ovulating or not are now available. Some symptoms may give clues to the timing of ovulation.
Increase in Basal Body Temperature
Progesterone is a hormone released from the corpus luteum after ovulation. It plays an essential role in preparing the uterus for pregnancy for it to be able to receive, implant, and support the fertilized egg at the beginning of pregnancy. Progesterone also has potent effects on the hypothalamus, including increased basal body temperature. Basal body temperature is the lowest natural, non-pathologic body temperature noted after rest.
During ovulation, there is an expected rise in body temperature. Therefore, a woman may take her temperature with a thermometer in the morning before doing any activity. There is approximately a 0.5 to 1-degree Fahrenheit increase compared to menstruation’s follicular phase. It is beneficial to note that the menstruation cycle can be divided into phases which include follicular, before the release of the egg; ovulatory, where the egg is released; and luteal, which happens after the egg is released. Thus, temperature changes during one’s cycle can indicate the best time to engage in sexual intercourse if one wishes to conceive.
Another test is directly measuring serum progesterone levels during the mid-luteal phase. If the egg is not fertilized, the corpus luteum degenerates and stops producing progesterone.
