Evaluation of Ovulation
Ovulation occurs as a result of a cascade of events that occur between the brain and the ovary. In addition, the hormonal milieu and homeostasis and stability within the human organism are critical factors in this process. Irregular cycles suggest that ovulation is not occurring while regular cycles may indicate ovulation, but not necessarily so.
The hypothalamus and pituitary gland are specialized areas of the brain that control the stimulating hormones necessary for the endocrine system. Gonadotropins (hormones secreted by the pituitary) stimulate the ovarian follicles (egg sacs) to grow and produce a mature oocyte ("egg"). This is followed by release of the egg ("ovulation"). The ovary also produces hormones that prepare the lining of the uterus ("the endometrium") for implantation and development of the embryo.
Evaluation of ovulation is an important initial step in the evaluation of infertility. Its evaluation is based on the secretion of progesterone by the ovary after ovulation. The following tests are used to check for ovulation.
Basal Body Temperature (BBT)
The patient is asked to take her daily oral temperature early in the morning before getting out of bed. Then patient records her temperature daily and brings it to the office for interpretation. There are several patterns; one is a monophasic pattern in which there are some variations from day-to-day. However, there is no exact rise of temperature to suggest ovulation. The second variety is what called a biphasic curve during which a temperature rise of approximately 0.7-0.9 degrees F occurs at midcycle and is maintained for 12-14 days. The temperature rise will subside if the patient does not conceive and remains elevated if pregnancy occurs.
Ovulation Prediction Kits
These kits measure the level of leutenizing hormone or LH in a woman's urine. LH is found in high level in the urine just before ovulation, which generally occurs within 12-24 hours after the rise of LH has been detected. Persistent failure of the test to turn positive may indicate a problem with ovulation.
Serum Progesterone Level
The patient is sent to the laboratory for the evaluation of serum progesterone level to confirm ovulation. Serum progesterone is secreted in high quantities by the ovaries after ovulation and also by the placenta during pregnancy. A level of serum progesterone above 3 ng/ml in the midluteal phase or approximately days 20-22 of the cycle is very highly suggestive of ovulation.
The preparation of the endometrium, which is the lining of the uterus for embryo implantation and growth, depends on estrogen and progesterone secreted by the ovary during the ovulatory cycle. This test is sometimes used to evaluate the ability of the endometrium to respond to progesterone, which is necessary for implantation. After a specimen is obtained in the office on approximately day 26 of the cycle, it is sent to a pathologist to determine if the uterine lining is in phase with the ovary.