What tests can be carried out?
Women may be asked to have a cervical smear test and both partners are usually given a urine test, to rule out sexually transmitted diseases, such as chlamydia.
The woman may need to give blood samples around seven days before she is due to start menstruating, to check that she is ovulating normally, and men are usually asked to provide a semen sample, which can then be analysed in the laboratory to check the quantity and motility of the sperm, among other things.
If all these tests come back clear, then the woman may need to undergo ultrasound scans and X-rays of the pelvis, which should be able to show up any blockages. It may be that more invasive checks are needed, such as a hysteroscopy or laparoscopy.