While the post coital test (PCT) has been proven not to be of value as a predictor of fertility, the findings on a PCT are actually a bioassay of changing hormone patterns. Therefore an understanding of its findings are useful in understanding the effects of estrogen and progesterone on the cervix.
Credits: Serono Laboratories
The pattern on the left-hand side of the slide under A demonstrates normal ferning of cervical mucus. The peaking of the estrogen levels prior to ovulation makes the cervical mucous secretions thin and capable of ferning. Mucus at midcycle is greater than 95% water and is typically thin, clear, acellular, and abundant. The stretchability of the mucus or "Spinnbarkeit" is 8 to 10 cm. On the right-hand side of the slide, the lack of ferning is consistent with a thick cervical mucus. This change in cervical mucous is attributed to the presence of progesterone produced by the corpus luteum. The rhythm method of contraception utilizes changes in cervical mucous to document fertile periods. .