If there is no known cause of infertility identified in the evaluation of an infertile couple, then it is termed unexplained infertility. This occurs in 5% to 10% of couples trying to conceive. It is more common in males than females for unknown reasons. See Box 12.1 for a summary of the main causes of primary and secondary infertility in men and women.

Box 12.1 Summary of the causes of primary and secondary infertility in men and women

  • The woman does not ovulate (produce an egg).
  • The egg does not reach the correct location for fertilisation because the fallopian tube(s) are blocked.
  • The man produces insufficient or abnormal sperm.
  • The sperm cannot reach the egg because the spermatic tube is blocked.
Last modified: Thursday, 26 June 2014, 8:30 PM