The fractional postcoital test: how to do it.

Procedure for the fractional postcoital test is described in a question-and-answer format. The time of the test is determined by a "rule of 2": 2 days before rise in basal body temperature after 2 days of abstinence and within 2 hours of coitus. A smear from the posterior fornix is taken and set aside. Cervical mucus from the internal os is then withdrawn via a polyethylene suction catheter sized to conform to the diameter of the external os. The specimen is examined in a 400-power field. The lower limit of normal motile sperm count is 5 per high-power field; an "excellent" result is 10 or more. If no sperm are seen the smear from the posterior fornix is examined and if again no sperm are found azoospermia or coital difficulties may be suspected. When sperm are found at the external os but not at the internal os a cervical cause of infertility has been found; this condition may go undetected by the Sim-Huhner test.