Final answer:
About 30 percent of infertility in couples is due to male factors, with an equal percentage due to female factors and the rest due to combined issues or unknown causes. Risk factors for male infertility include lifestyle choices, certain medical treatments, and age. IVF success rates decrease with the woman's age.
Step-by-step explanation:
When examining the question of infertility, it's noted that approximately 30 percent of infertility is due to male factors. Similarly, around 30 percent of infertility can be attributed to female factors. The remaining cases are a result of issues with both partners or unknown causes. Male infertility may be influenced by a variety of risk factors including heavy alcohol use, smoking, environmental toxins, certain medications, age, and illnesses such as kidney disease or cancer treatments that involve radiation or chemotherapy. The IVF success rate is highly dependent on the age of the woman, with more than 40 percent of women under 35 successfully giving birth post-IVF. In contrast, this success rate significantly declines to just over 10 percent for women aged over 40. Infertility itself is a broad issue, affecting about ten percent of women aged 15 to 44 in the U.S., and is defined as the inability to reproduce after one year of regular, unprotected sexual intercourse.