This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infertility, Subject name: Gynaecology & Obstetrics
Ferning of cervical mucus (fern test) is due to: 
Select and explain. 
A. Presence of NaCl under progesterone effect, B. Presence of NaCl under estrogenic effect, C. LH/FSH, D. Mucus secretion by Glands
B: Presence of NaCl under estrogenic effect
Answer: B: Presence of NaCl under estrogenic effect 
Explanation: Fern test- A specimen of cervical mucus obtained using a platinum loop or pipette is spread on a clean glass slide and allowed to dry. When viewed under low power microscope during the estrogenic phase, a characteristic pattern of fern formation is seen. Ferning is due to the presence of high NaCl and low protein content in the mucus secreted under high estrogen effect in the midmenstral phase prior to the ovlation. Shaw's textbook of gynaecology -16th edition-page no 256.