Luteinizing hormone (LH) is a reproductive hormone produced in the pituitary gland and plays a vital role in regulating a woman’s menstrual cycle and enabling fertilization and conception. Women of child bearing age will experience a measurable rise in LH sometime around mid-cycle. This increase is known as the LH surge and generally takes place between 12 – 48 hours prior to ovulation, the release of an unfertilized egg from the ovary, with the average time of occurrence in most women being approximately 36 hours before this event.
The LH surge plays an important part in monitoring fertility in couples who are trying to get pregnant. Once the LH surge occurs, most women, with regular menstrual cycles, will ovulate within the next one to two days. Other changes may occur as well, such as changes in body temperature and in the amount and quality of cervical mucus. These events are also the result of the LH surge, but can vary in degree from one female to the next and are not always the most reliable indicators of ovulation. Using most commercially available ovulation tests, the increase in LH can be measured and ovulation predicted so that couples can accurately time their efforts to conceive. Conception, if it is going to occur, will result from having intercourse within three days prior to or one day following ovulation.
When you measure your LH surge, it is very important that you use the same brand ovulation kit at the same time each day. Many women find that they receive the most accurate results if they test after 10am. Additionally, it is strongly recommended that fluids are not consumed within two hours of measuring the LH surge as fluid intake may dilute and possibly produce inaccurate test results. With these guidelines in mind, measuring the LH surge in this manner can be a valuable yet relatively inexpensive way for couples to concentrate their efforts and produce the best possible outcome.