Fertility issues have multiple causes, and often both partners contribute to the difficulty:
- In roughly 30% of cases, an identifiable problem is found in the female partner
- In another 30%, in the male partner
- In 20%, in both
- In 20%, no specific cause is identified (unexplained infertility)
Caues of Male Infertility
Low sperm count results from problems with sperm production in the testes due to genetic factors, hormonal imbalances, heat exposure, varicocele (enlarged veins in the scrotum), infections, medications, or lifestyle factors (smoking, heavy alcohol use, drug use). Poor sperm motility or abnormal morphology can stem from similar causes. Complete absence of sperm (azoospermia) can result from blockage in the reproductive tract or failure of sperm production.
Causes of Female Infertility
Ovulation disorders (PCOS, thyroid disease, elevated prolactin) prevent regular egg release. Tubal damage or blockage from endometriosis, pelvic inflammatory disease, previous surgery, or infection prevents sperm from reaching the egg. Endometriosis (tissue growth outside the uterus) causes inflammation and adhesions affecting fertility. Hormonal imbalances (low progesterone, luteal phase defect) may prevent proper uterine preparation for implantation.
Age is the most significant factor because female fertility typically peaks in the 20s and declines progressively, with significant acceleration after age 35.
Lifestyle and Other Factors
Smoking, heavy alcohol use, recreational drug use, obesity, severe underweight, excessive exercise, and chronic stress all impair fertility in both men and women. Certain medications and medical conditions (diabetes, thyroid disorders, autoimmune conditions) affect fertility. Previous use of some contraceptives (like hormonal birth control) does not permanently affect fertility as well, although fertility typically returns within 1–3 months of stopping.