Ovarian reserve refers to the number of eggs that remain in the ovaries at a given moment. A woman is born with approximately one to two million eggs, stored in tiny fluid-filled sacs called follicles. That number decreases gradually over time, reaching around 300,000 to 400,000 by puberty, and only a few hundred will be released through ovulation during a lifetime.
This gradual change is a natural part of reproductive biology, and its pace varies from person to person. That is why age, although important, is not the only factor specialists consider. Genetics, medical history, and certain surgeries or conditions may also play a role.
How it is measured
There are two common ways to estimate it. The first is a blood test that measures anti-Müllerian hormone, known as AMH, which is produced by the small follicles in the ovaries and can generally be taken on any day of the menstrual cycle. The second is an antral follicle count, a transvaginal ultrasound usually done at the beginning of the cycle, in which a specialist counts the small follicles visible in each ovary.
Sometimes other hormones, such as FSH and estradiol, are also measured on specific days of the cycle to complete the picture. A specialist interprets all these results together with age and medical history, rather than looking at a single number on its own.
What the results can and cannot tell
A result from an ovarian reserve evaluation is a snapshot of the present, not a prediction of the future. It describes quantity, while egg quality is a separate part of the fertility picture and is closely related to age. A lower or higher number does not, by itself, determine whether someone can become pregnant. In fact, some conditions, such as polycystic ovary syndrome, can be associated with higher AMH levels.
Why it matters when planning
Knowing more about ovarian reserve can be useful for people thinking about their reproductive timeline, whether they plan to try for a pregnancy soon, later, or are considering options such as egg freezing or IVF. Specialists use these results to guide conversations about timing and to anticipate how the ovaries may respond to fertility treatments.
Beyond testing, everyday habits are commonly associated with overall reproductive health, such as regular gynecological check-ups, a balanced diet, physical activity, and avoiding tobacco. While they cannot change the number of eggs a person has, they contribute to general well-being at every stage of life.
A starting point for the conversation
Evaluating ovarian reserve is not necessary for everyone, but it can offer helpful context. Talking with a fertility specialist about personal history, goals, and questions is the best way to know whether this evaluation makes sense in each situation and what the results may mean.