text: The sperm has to pass from the vagina through the cervix to the uterus and ultimately to the fallopian tubes to meet the egg. The cervical canal is very narrow and is filled up with mucous through which the sperm has to pass. Therefore, problems in the structure of the cervix or type and texture of the mucous can prevent the sperms to pass through it. This may happen if
  There is improper hormonal effect on the cervix (lack of estrogen). The mucous in this case is very thick.
  Infertility also occurs if the endometrium is unprepared for embedding the fertilized egg. This may happen if
  The hormonal action on the endometrium is not proper so that it remains thin and unprepared to implant the egg.
  As an after effect of operations like curettage of endometrium or abortions, the two layers of endometrium may stick together causing infertility.