The process of declining fertility is universal and increases with age. However, the timing of this phenomenon is variable and may begin to occur in young women. Therefore, even young women need evaluation for decreased ovarian reserve.
Ovarian reserve is the term used to describe the ability of a woman’s ovaries to produce eggs that will ultimately produce a baby. As already discussed, age is an important determinant of ovarian reserve, but ovarian reserve can be severely affected even in younger women. This decline in ovarian reserve can occur due to surgery, smoking, cancer treatments, or simply a woman’s genetic make-up. To assess a woman’s ability to achieve a pregnancy, doctors will conduct an evaluation of her ovarian reserve using tests that measure important components of the reproductive system.
The evaluation process typically begins with a test to measure the naturally-occurring hormones FSH (follicle stimulating hormone), LH (luteinizing hormone) and estradiol. These hormones are measured on cycle day 2, 3, or 4. (Day 1 is defined as the first full day of menstrual flow.) The FSH level is the most important of these three tests. The measurements of LH and estradiol mainly provide a more precise understanding of FSH levels. FSH levels increase as a woman ages. Women with abnormal FSH levels often have difficulty conceiving and if a conception occurs there is an increased chance of a miscarriage (fig. 4).
A more sensitive test used to evaluate ovarian reserve is the Clomiphene Citrate Challenge Test (CCCT). In this test, women are treated with the ovulation induction agent clomiphene citrate (Clomid, Serophene) for five days. Prior to and following treatment, the woman’s FSH and estradiol levels are measured. If FSH levels are abnormal, the chances of conception and a successful pregnancy are poor.
Another specialized test to measure ovarian reserve is the basal follicle count (fig. 5). Early in the menstrual cycle, doctors use ultrasound to count a woman’s small follicles. A low number of follicles indicates a poor response to therapy and a lower chance of conception and pregnancy. Very high numbers of small follicles may indicate a tendency for the woman to over-respond to hormonal stimulation.
While each of these tests is important, there is no clear measure that applies to all women at every age. These tests should be considered as a part of a larger assessment that incorporates the patient’s age, response to previous treatment, and other factors. A doctor will review many factors in assessing a woman’s health and chances of achieving a pregnancy.
fig. 4: Scott, RT, et al. Fertil Steril in submission, 2006
fig. 5: Basal antral follicle ultrasounds. RMA photos