Is being underweight associated with infertility?

Low body weight may be associated with lower fertility, especially if you also have irregular periods or no cycles (amenorrhea). This means that you’re not ovulating (releasing an egg) every month. This can be due to low levels of hormones that control your cycles from the pituitary gland, known as hypogonadotropic hypogonadism, which is more common in women who are significantly underweight, or may be due to stress, eating disorders, or heavy exercise such as long-distance running.