This approach is used for women who have irregular menstrual cycles or if they are not ovulating. Normally this is done in conjunction with the injection of sperm into the female reproductive tract in order to facilitate fertilization. This method is recommended for mild cases of endometriosis, male factor infertility or when causes of infertility are unexplained. Success rates for this method are a result of ovulation induction which causes 3-4 eggs to develop instead of the usual 1-2 in a natural cycle. The risk of multiple pregnancy rises significantly if more than 3-4 eggs develop. There are different methods of ovulation induction using different types of drugs. If a woman menstruates every 22-32 days than it is almost certain that she is ovulating regularly and thus obviates the use of ovulation monitoring.