What are the causes of low sperm count or abnormal sperm function in men? Low sperm count or abnormal sperm function may be caused by different things. These include: Undescended testicles Genetic defects/DNA damage Diabetes Prior bacterial or viral infections such as mumps or adenovirus Trauma or prior surgeries on the testicles or inguinal region Enlarged veins (varicoceles) in the testes that can increase blood flow and heat, both of which affect the number and shape of the sperm Exposure to chemicals like pesticides, radiation, and chemotherapy Alcohol use, marijuana use, and tobacco smoke Steroid use Overexposure to heat (such as in saunas and hot tubs) Surgical removal of one of the testicles due to cancer In addition, there can be problems with the delivery of sperm and subsequent fertilization due to any of the following: Premature ejaculation Damage or injury to the reproductive organs Semen entering the bladder instead of emerging through the penis during orgasm (retrograde ejaculation) Certain genetic diseases (such as cystic fibrosis) Men who have previously had a vasectomy and wish to father a child have two choices. They either need to have the vasectomy reversed or have sperm retrieved through a surgical procedure as part of assisted reproductive techniques . Advanced Fertility Care Centre, Maternal & Child Health Care , Ashwini Hospital & Fertility Centre Moondrumavadi Madurai -07, Best Fertility Care Centre