Dr. Natalie Crawford: Egg counts crash after 32, plan now

Women are born with all the eggs they will ever have: ~1–2 million at birth, ~300,000 in reproductive years, ~20,000 by age 37, and fewer than 1,000 at menopause. Each month a cohort of eggs leaves the ‘vault’; one ovulates, the rest die. Around 35, both egg number and egg quality begin to decline more steeply. By 35, miscarriage risk is ~25%; by 40 it's ~50%. Monthly chance of pregnancy drops from ~20% at 30, to 10–15% at 35, to ~5% at 40. If you want 2–4 children and plan to start in your mid-to-late 30s, you are statistically relying on low odds unless you intervene (e.g., IVF/embryo banking) earlier.

Ovarian reserve is essentially “how many eggs are left in the vault,” commonly measured by AMH blood test and an antral follicle count (ultrasound of how many small follicles are visible in a given month). A low reserve does *not* reduce your chance of conceiving in a given month (that’s driven mostly by age-related egg quality), but it does reduce the *total* window and the number of eggs an IVF cycle can retrieve. Professional bodies like ACOG advise against AMH testing in women not yet trying, arguing it causes anxiety; Crawford argues the opposite—that women deserve this data to decide on timing, egg freezing, lifestyle changes, and avoid later regret.

Men produce 200–300 million sperm per day (about 1,500 per second), with a ~90-day sperm lifecycle (72 days of production + ~18 days of transport/storage). Sperm counts have fallen ~50% in 50 years, with decline accelerating in the last decade. Modifiable harms include cigarette smoking, marijuana, likely vaping, chronic heat to the testes (daily hot tubs, intense cycling, saunas, laptop on lap, very hot baths), obesity, poorly controlled metabolic disease, and exogenous testosterone (TRT) which can shut down sperm production and sometimes cause irreversible azoospermia. Because new sperm are made continually, targeted lifestyle improvements over 3–6 months can meaningfully improve semen parameters.

The brain constantly asks, “Can this body safely sustain a pregnancy now?” Chronic stress, sleep deprivation, under- or over-exercising, high inflammation and metabolic disease all push it toward ‘no’ by suppressing FSH/LH, disrupting ovulation, and lowering sperm production. Crawford highlights: 7.5–8 hours of sleep as the single most neglected fertility tool; minimizing processed foods, added sugars, processed meats and excess red meat; emphasizing fruits, vegetables, fiber, healthy fats and moderate fish; avoiding smoking, marijuana, cocaine, heavy alcohol (≥4 drinks/week already shows associations), frequent plastic heating (microwaving in plastic, takeout in hot plastic/foam, Teflon pans, thermal receipts); and maintaining moderate, consistent exercise—enough to reduce obesity and insulin resistance, but not at extreme athletic levels that shut down ovulation.

A healthy menstrual cycle is regular and predictable for the individual (roughly 24–35 days). Irregular cycles or no periods (off hormonal contraception) can signal PCOS, hypothalamic dysfunction (from under-eating, over-exercising, or severe stress), thyroid issues, pituitary disorders, or premature ovarian failure. In PCOS, women are often born with a larger ‘vault’ of eggs; too many follicles dilute FSH, no single egg matures consistently, ovulation is sporadic, and the ovary overproduces testosterone—leading to acne, hair growth, insulin resistance, abdominal weight gain, and infertility. In endometriosis, inflammatory implants of endometrial-like tissue cause severe period pain, pain with sex, scarring, blocked tubes, and embryotoxic inflammation—often without altering cycle length. Both conditions raise risks beyond fertility (e.g., endometrial cancer in PCOS patients who don’t bleed, osteoporosis and cardiovascular risk in long-term low-estrogen states).