Inability to conceive a child even after frequent unprotected intercourse for a year or more is then called as infertility. Causes can be from male side or from side of female partner or in both partners.
Male Impotency :
Impotency is when a man is unable to get or keep an erection that allow to take part in sexual intercourse or other types of sexual activities. There can be other problems like premature ejaculation or loss of sex drive due to numerous diseases and stress of day to day life.
Sperm Problem :
Problem in sperm production, quality and transportation causes infertility in males. There are numerous causes of these problem.
Female :
Infertility in females may have complex causes and many times it is difficult to detect one. Most important and common ones being PCOS which causes problems in ovulation or there can be some hormonal imbalance which can lead to infertility. There may be some pathological problems to like blockage in fallopian tubes which stops egg from reaching uterus and subsequently infertility results.