The science of fertility: Hormones, inflammation, and what you can control | Dr Natalie Crawford

What It Covers

Dr. Natalie Crawford, reproductive endocrinologist and author of The Fertility Formula, explains the science of fertility optimization. She covers how chronic inflammation impacts egg and sperm quality, why tracking ovulation matters more than apps suggest, the connection between metabolic health and conception, and specific lifestyle interventions around sleep, stress, and nutrition that influence reproductive outcomes before attempting pregnancy.

Key Questions Answered

• •Infertility prevalence shift: Infertility rates in the United States increased from one in eight couples to one in five couples. This rise reflects not just delayed childbearing but global increases in chronic inflammatory disorders, declining sperm counts, and reduced ovarian reserve. The medical standard of waiting twelve months before testing wastes valuable time when simple assessments like semen analysis and AMH testing could identify issues immediately and enable proactive intervention.
• •Ovulation tracking accuracy: Period tracking apps that rely solely on cycle day one input accurately detect ovulation only 20% of the time. Women should use fertility awareness methods including cervical mucus monitoring (sticky, stretchy, egg-white consistency indicates peak estrogen), basal body temperature shifts (0.4 degree Fahrenheit rise after ovulation), or urinary LH detection. Using two methods together increases monthly pregnancy probability more than relying on apps alone.
• •Luteal phase dysfunction: The first stage of ovulatory dysfunction presents as a shortened luteal phase under eleven days, occurring before cycles become obviously irregular. This indicates the corpus luteum cannot sustain progesterone production long enough, often due to chronic inflammation interfering with brain-ovary communication. Women can identify this by tracking ovulation timing and cycle length, enabling early intervention before infertility develops.
• •Male fertility factors: Sperm quality contributes to 50% of infertility cases (one-third female factors, one-third male factors, one-third combined). Men generate new sperm every three months, making quality highly responsive to lifestyle changes. Testosterone replacement therapy alone suppresses sperm production and can cause irreversible azoospermia. Men wanting children should use alternatives like Clomid or combine TRT with HCG injections while monitoring semen analysis results.
• •Sleep and reproductive hormones: Each hour of sleep deficit correlates with fewer eggs retrieved during IVF. FSH and LH release from the brain occurs in early morning after adequate sleep duration. Women require seven to nine hours nightly, particularly during the luteal phase when progesterone production demands higher metabolic resources. Sleep variability and inconsistent circadian rhythms associate with higher infertility rates in both partners regardless of total hours.
• •Birth control pill limitations: Hormonal contraceptives suppress FSH and LH to near-undetectable levels, eliminating cervical mucus changes, basal body temperature shifts, and normal ovulatory patterns. This prevents women from learning their baseline fertility signs for years. Progesterone IUDs can alter endometrial receptivity for up to twelve months after removal. Women should discontinue hormonal contraception six to twelve months before attempting conception to establish normal patterns.
• •AMH testing controversy: The American College of OB-GYN recommends against checking AMH (anti-Müllerian hormone) in women without infertility, citing concerns about unnecessary stress. However, low AMH at age 32 reveals either genetic factors or modifiable causes like autoimmune disease, endometriosis, smoking, or cannabis use. Early detection enables investigation of underlying inflammation, potential egg freezing when counts are higher, and informed reproductive timeline decisions.