There are some factors that contribute to infertility. These are the same in men and women:
Age: For a woman, the decline in fertility is more pronounced in her mid-30s. The reasons for this are related to both, the number and quality of the eggs as they age. It may be related to health problems that may interfere with fertility. For men, the effect of age on fertility is seen at ages over 40 years.
Tobacco: If either partner smokes, it reduces the chances of conception as well as any benefit of fertility treatment. If a woman smokes, it increases the chance of miscarriage. Smoking contributes to sexual disorders such as erectile dysfunction and reduces sperm count in men.
Coffee and alcohol: Drinking too much coffee or too much alcohol can impair a woman’s fertility. Moderation is the key-1-2 cups of coffee would be fine. For women, there’s no safe level of alcohol use during conception or pregnancy. Alcohol use may also make it more difficult to become pregnant as well as increases the risk of birth defects.
BMI: A high BMI and an inactive lifestyle reduces your chances of conception. Also, a man’s sperm count and testosterone levels may be adversely affected if he is overweight. A lower than normal BMI also increases the risk of infertility in women especially those with eating disorders.