This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
What is the microscopic finding of cervical mucus during post-ovulatory period? 
Select and explain. 
A. Shows pattern on drying, B. Is thick, C. Is thin and cellular, D. Is thin and alkaline
A: Shows pattern on drying
Answer: A: Shows pattern on drying 
Explanation: Dried cervical mucus examined microscopically has characteristic patterns dependent on the stage of the ovarian cycle. Mucus crystallization necessary for the production of the fern pattern is dependent on an increased sodium chloride concentration. Cervical mucus is relatively rich in sodium chloride when estrogen, but not progesterone, is being produced. Thus, during post-ovulatory cycle from approximately the 7th to the 18th day of the cycle, a fernlike pattern is seen. Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 8. Prenatal Care. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.