Know your fertility numbers before you need them
September 29, 2026 · 20 min read
Natalie Crawford, Huberman and Michael Eisenberg recommend testing ovarian reserve and sperm quality early, and explain how age and lifestyle affect both. Earlier knowledge gives people real options instead of late surprises.
The rules, numbers and steps worth keeping in front of you.
- Measure fertility early: AMH and antral follicle count for women, semen analysis for men.
- Natalie Crawford: the egg supply is fixed before birth and shrinks every month regardless of the pill or pregnancy.
- Crawford: typical follicle counts are 16 to 20 at 30, 14 to 16 at 35, 8 to 10 at 40, with a steep drop around 37.
- Crawford: the best age to freeze eggs is about 32 to 33.
- Crawford: the pill can lower AMH by up to 30 percent, reversibly; retest after a few months off.
- Crawford: periods should be under 35 days apart and predictable; a shortening cycle can signal falling reserve.
- Crawford: 20 eggs frozen at 30 may yield about four normal embryos; freezing is not a guarantee.
- Andrew Huberman: chance of conceiving per cycle is about 20 percent at 30 or younger, 1 to 3 percent at 40 or older.
- Huberman: at 38 and up, consider seeing an OB-GYN at the outset.
- Huberman: semen analysis after 48 to 72 hours of abstinence, repeated about every five years.
- Michael Eisenberg: the man contributes to about half of infertility and is bypassed about a third of the time.
- Eisenberg: bank sperm before testosterone therapy; Crawford says before a vasectomy too.
- AMH does not predict this month's odds of conception; that is ACOG's objection to routine screening.
- Have results interpreted by an OB-GYN, reproductive endocrinologist or urologist.
This is the short form. The full insight has every expert's reasoning, their own words and the sources.