Let’s discuss ovarian reserve. It’s defined as the number of oocytes, or eggs, left in your ovary. Clinically, ovarian reserve is measured using hormone levels and features seen in ultrasound imaging. Traditionally, reproductive aging was considered to be due to the principle that human eggs peak during fetal life, and don’t regenerate.

As the number of oocytes (or eggs) decrease with age, women experience reproductive and ovarian deterioration. For women in the later stages of reproductive aging, like perimenopause and menopause—when menstrual cycles are irregular—ovarian reserve is often lower than it was during prime fertility. Egg reserve can be indirectly measured using hormone levels or ultrasound imagery.

A newborn girl is born with approximately 500,000 to 1 million oocytes. Over time, the number of oocytes depletes slowly due to the natural process of atresia. This is the degeneration and resorption of several follicles and their ovules prior to the maturation and release of one ovule from a follicle and then ovulation. This normal deterioration process ultimately leads to menopause.

There are different measures to evaluate ovarian reserve. These include biochemical tests and ultrasound imaging of the ovaries. Biochemical measures are intended to measure the pool of oocytes or follicles, directly or indirectly.

Glycoprotein hormones like Inhibin B and anti-müllerian hormone (AMH) are produced by small ovarian follicles. These hormones help identify the size of this pool of eggs. As the number of ovarian follicles declines with age, concentrations of these hormones also decrease. So, testing for these hormones early in the menstrual cycle gives some measure of egg numbers and ovarian reserve.

Basal Serum follicle stimulating hormone or FSH and estradiol levels, E2, are also used as markers of ovarian reserve. Elevated basal serum FSH is indicative of a diminished ovarian reserve. Basal E2 alone is not used as a screening measure for DOR, yet it aids in the correct interpretation of a normal basal serum FSH value.

For example, a high basal FSH or E2 level early in the cycle suggests impaired oocyte development—a worrisome sign of reproductive aging and failure ahead in an IVF cycle.

Another measure of ovarian reserve is the Clomiphene Citrate Challenge Test (CCCT), which includes measurements of serum FSH before and after treatment with Clomiphene citrate. An elevated FSH concentration after stimulation indicates a diminished ovarian reserve.

When it comes to screening for ovarian reserve, AMH is a more sensitive measure than FSH as it declines before FSH rises. Thus, AMH has replaced basal FSH and E2 level testing as a biomarker of ovarian reserve. Ultrasonographic measures of ovarian reserve include the antral follicle count (AFC) and ovarian volume. AFC represents the sum of antral follicles in both ovaries, as observed by ultrasound in the early part of the menstrual cycle.  AFC can range from 3-30 follicles, with most women having between 12-24 follicles. However, keep in mind that a good number can vary greatly and depends on several factors, including age. The question arises, which patients should undergo ovarian reserve testing? Of course, the treatment and guidance ought to be individualized based on things like age and diagnoses. But, it’s critical to remember that ovarian reserve tests should not be the sole criteria used to deny patient access to assisted reproductive technologies or treatments.

In conclusion, while AMH and AFC are the most sensitive and reliable measures of ovarian reserve, they have shown to be good predictors of egg yield but poor independent predictors of reproductive potential. Therefore, it’s vital not to use them as an absolute fertility test or to deny access to infertility treatment. However, evaluate your individual situation carefully, including insurance coverage and the cost of IVF versus the benefit and chances of a full term pregnancy.