Biology and health

1. Delayed childbearing.
   1. Female reproductive aging.
   2. Male reproductive aging.
   3. Infertility and subfertility.
   4. Desired versus achieved fertility.
2. Possible changes in reproductive health.
   1. Sperm counts and male fertility.
   2. Obesity and metabolic health.
   3. Environmental exposures.
   4. Evidence, uncertainty, and competing explanations.