Risk factors

Many of the risk factors for both male and female infertility are the same. They include:

• Age. Women's fertility gradually declines with age, especially in the mid-30s, and it drops rapidly after age 37. Infertility in older women is likely due to the lower number and quality of eggs, and can also be due to health problems that affect fertility. Men over age 40 may be less fertile than younger men.
• Tobacco use. Smoking tobacco or marijuana by either partner may reduce the likelihood of pregnancy. Smoking also reduces the possible effectiveness of fertility treatment. Miscarriages are more frequent in women who smoke. Smoking can increase the risk of erectile dysfunction and a low sperm count in men.
• Alcohol use. For women, there's no safe level of alcohol use during conception or pregnancy. Alcohol use may contribute to infertility. For men, heavy alcohol use can decrease sperm count and motility.
• Being overweight. Among American women, an inactive lifestyle and being overweight may increase the risk of infertility. For men, sperm count also may be affected by being overweight.
• Being underweight. Women at risk of fertility problems include those with eating disorders, such as anorexia or bulimia, and those who follow a very low-calorie or restrictive diet.
• Exercise issues. A lack of exercise contributes to obesity, which increases the risk of infertility. Less often, ovulation problems may be associated with frequent strenuous, intense exercise in women who are not overweight.