Decoding Fertility: Understanding Ovarian Reserve and Age’s Impact – ARC Summit

We assess aging and fertility by measuring FSH levels during the first few days of the menstrual cycle, known as cycle day 3 ovarian reserve testing. Women with an FSH level under 10 mIU/ml are in the best prognosis group. Higher FSH levels indicate older, more resistant eggs, especially as women age and their FSH levels naturally increase.

I often share a chart with patients that illustrates peak fertility between ages 18 to 25. At 25, the chance of pregnancy is about 35% per month, with a miscarriage rate of only 10%, resulting in an overall live birth rate of about 30% per month. By age 35, the conception rate decreases to about 20% per month. The eggs left are often of lower quality with more chromosomal abnormalities, leading to a higher miscarriage rate of 25%, and reducing the live birth rate to about 15% per month.

At 40, the conception rate drops further to 10% per month, with 40% of pregnancies resulting in miscarriage, and an overall live birth rate of 6%. The body compensates for aging eggs by increasing FSH production, which can lead to a higher chance of releasing multiple eggs and, subsequently, a greater likelihood of twins after age 35.

For women over 35, waiting 12 months to evaluate fertility is impractical; instead, evaluation is recommended after just 6 months. Anti-Müllerian hormone (AMH) levels, usually desired between 1.5 to 2, are also used to estimate ovarian reserve. AMH is produced by granulosa cells surrounding the eggs—the more eggs you have, the higher the AMH. A low AMH level can indicate accelerated aging and fewer available eggs.