Postcoital test (PCT) is done for:

Post coital test (Sim's/Huhner's test): The couple is advised to have intercourse around ovulation preferably in the early hours of the morning. The women presents herself in the clinic within 2 hours of intercourse. The mucus is aspirated from the cervical canal and spread over glass slide. Smear from the posterior fornix acts as a control. Usually 10-50 motile(progressive motility) sperms are seen. If the count is <10, proper semen analysis is to be done. Advantage of this test is that cervical mucus can be simultaneously studied for oestrogenic effect(ie ferning) and ovulation, it's capability to allow sperm penetration and the presence of any antisperm antibodies(shaky or rotatory movement of the sperms). reference: Shaw's Textbook of Gynaecology-16th edition-Page no 243.