Egg quality refers to the genetic health of the egg, specifically its chromosomal integrity and ability to support fertilization and embryo development. A high-quality egg is chromosomally normal (euploid), containing the correct number of chromosomes necessary to form a healthy embryo. The primary factor influencing egg quality is age, as the percentage of chromosomally abnormal eggs increases significantly as a person gets older. Standard clinical tests do not directly measure this genetic quality but instead assess a woman’s ovarian reserve, which is the number of eggs remaining. This assessment of quantity helps guide fertility planning and predicts the likely response to treatments.
Assessing Ovarian Reserve Through Blood Tests
The Anti-Müllerian Hormone (AMH) blood test is one of the most reliable hormonal tests for estimating the remaining egg supply. AMH is produced by the granulosa cells surrounding pre-antral and small antral follicles in the ovaries. The concentration of AMH in the bloodstream directly reflects the size of this pool of small follicles, which represent the eggs available for future development.
A higher AMH level suggests a larger ovarian reserve, while a lower level indicates a diminished reserve. Low AMH may predict a poorer response to ovarian stimulation medications used in treatments like in vitro fertilization (IVF). Since AMH levels are relatively stable throughout the menstrual cycle, this test can be performed at any time. The result offers a snapshot of egg quantity and helps clinicians tailor treatment protocols.
Follicle-Stimulating Hormone (FSH) and Estradiol (E2) levels are typically measured together on Day 3 of the menstrual cycle, when hormone levels are at a baseline. FSH is secreted by the pituitary gland and signals the ovaries to mature an egg. If the ovarian reserve is low, the ovaries are less responsive, causing the pituitary gland to release more FSH to stimulate the remaining follicles. Therefore, an elevated Day 3 FSH level suggests a diminished ovarian reserve.
Estradiol is measured simultaneously because high levels of this hormone can artificially suppress the pituitary gland’s release of FSH. If Day 3 Estradiol is high, a seemingly normal FSH result may be misleading. The elevated estrogen prevents FSH from rising to the level that truly reflects ovarian function. Interpreting these two hormone levels together provides a more accurate picture of the communication pathway between the brain and the ovaries.
Imaging Methods for Follicle Counting
The Antral Follicle Count (AFC) is a non-hormonal, visual assessment method used alongside blood tests to estimate ovarian reserve. This count is performed using a transvaginal ultrasound, typically during the first few days of the menstrual cycle. The procedure allows the physician to visualize and count the number of small, fluid-filled sacs present on the surface of both ovaries.
These small sacs are known as antral follicles, and they contain immature eggs recruited for that particular cycle. The follicles counted usually measure between 2 and 10 millimeters in diameter. Since each antral follicle holds a potential egg, the total AFC serves as a physical estimate of the accessible egg supply.
A higher antral follicle count correlates with a better capacity for the ovaries to produce multiple eggs in response to fertility medications. Conversely, a low AFC suggests a reduced ovarian reserve. The AFC provides a physical confirmation of the hormonal blood test results and is a strong predictor of how many eggs may be retrieved during an IVF cycle.
Interpreting Results: Quantity Versus Quality
The combined results from the AMH, FSH, and AFC tests provide a comprehensive assessment of a patient’s ovarian reserve, or egg quantity. For example, low AMH, high Day 3 FSH, and a low AFC suggest diminished ovarian reserve. These findings inform the patient and physician about the potential need for intensive treatment or a faster timeline for fertility intervention. These markers primarily predict the ovarian response to stimulation, indicating the likely number of eggs that can be retrieved.
However, these tests do not measure the egg’s true quality, which is its genetic health. The most significant factor influencing egg quality remains the age of the individual. A person may have a normal ovarian reserve but still experience difficulty conceiving due to an age-related decline in the chromosomal integrity of those eggs.
The only definitive ways to assess an egg’s quality are invasive and occur after the eggs have been retrieved during an IVF cycle. Embryologists can perform a visual morphology assessment of the eggs and resulting embryos in the laboratory, but this provides limited information. The most detailed assessment is Preimplantation Genetic Testing for Aneuploidy (PGT-A). PGT-A involves biopsying the resulting embryo to screen for an abnormal number of chromosomes. This testing offers the clearest insight into the genetic potential of the egg, confirming whether it was chromosomally healthy enough to support a full-term pregnancy.