Regardless of marital status, approximately 12 percent of women age 15 to 44 in the United States experience difficulty becoming pregnant or carrying a pregnancy to term, according to the Centers for Disease Control and Prevention. After one year of unprotected sex, roughly 6 percent of married women are unable to become pregnant. Between 3.3 million and 4.7 million men who were sexually active and under age 45 reported visiting an infertility specialist in their lifetime.
Of men who sought assistance from an infertility doctor, 14 percent were diagnosed with sperm or semen problems, while 6 percent were diagnosed with varicocele, states the Center for Disease Control and Prevention. To ascertain fertility in a man, a specialist analyzes a semen sample for the number of sperm, morphology and motility. Conditions that lead to abnormal semen analysis include an overheating of a man's testicles, heavy alcohol use, exposure to environmental toxins, cystic fibrosis and diabetes.
Conditions that affect the fallopian tubes, ovaries or uterus lead to infertility in women, explains the CDC. Some causes include premature ovarian insufficiency, polycystic ovary syndrome, a history of gonorrhea or chlamydia, functional hypothalamic amenorrhea and endometriosis. Fibroids can grow on the uterus, also leading to fertility challenges.
In women younger than 35, 40 percent of those undergoing assisted reproductive technology became pregnant, while 31 percent of women age 35 to 37 were successful, 22 percent age 38 to 40 were successful and 2 percent of women age 44 or older were successful, states the CDC.