Once the eggs mature, the hypothalamus signals the pituitary gland (via GnRH hormone) to release a surge of luteinizing hormone which causes ovulation 34-36 hours later.  Predicting ovulation allows the couple to plan intercourse around the most fertile times.

Basal body temperature (BBT) charting was once the most widely used method to predict ovulation. Using this method, the body temperature is taken every morning prior to getting out of bed and entered on a chart.  This charting is done throughout the ovulatory cycle and a slight rise in temperature is seen on the day of ovulation.  The BBT charts are recorded monthly to establish an “ovulatory pattern”.  Once the ovulation history is determined, the chart can be used to predict future ovulatory time frames.

BBT charting has been largely abandoned with physicians preferring the urinary LH test kits. These kits very accurately measure the spike in LH that precedes ovulation which enables couples to time intercourse. The only advantage to BBT charting is that it incurs no cost other than the purchase of a BBT thermometer.

One indicator of successful ovulation is an increase in progesterone levels.  Progesterone is produced by the leftover follicular structures on the ovaries known as the corpus luteum. Low progesterone levels are one indication that “quality” ovulation may not have occurred.

Sometimes the vaginal probe ultrasound is used to document ovulation. The physician scans the ovaries prior to ovulation and visualizes the follicles. Near the predicted ovulatory time, the ovaries are examined to establish that the follicles ruptured and released their eggs.

Fertility Tests