Appropriate candidates for IVF are couples where: The woman has damaged or blocked fallopian tubes or ovulatory problems. The man has a mild case of male factor infertility such as a low number of healthy sperm. The cause of infertility is unknown. Appropriate candidates for ICSI are couples where: The man has a very low sperm count. The man has sperm that cannot move properly or is abnormal in other ways. The man has sperm that has been surgically retrieved. There has been a previous fertilization failure using conventional IVF.