Women’s fertility starts to decrease from the mid 20’s, and decreases fastest in he 40’s. Smoking, Sexually Transmitted Infections like Chlamydia, endometriosis, ovarian surgery, chemo- or radiotherapy for cancer can all reduce egg numbers and egg quality (ovarian reserve). Chlamydia, Pelvic Inflammatory Disease (PID), endometriosis or surgery can block one or both fallopian tubes. Being overweight or underweight may lower fertility. Infertility in men can be increased by testosterone or anabolic steroid use, being overweight, and heavy use of alcohol, marijuana, or narcotics.