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
Fern test is due to : 
Select and explain. 
A. Presence of NaCI under progesterone effect, B. Presence of NaCI under estrogenic effect, C. LH/FSH, D. Mucus secretion by Glands
B: Presence of NaCI under estrogenic effect
Answer: B: Presence of NaCI under estrogenic effect 
Explanation: Ans. is b i.e. Presence of NaCI under estrogenic effect Fern test is for documenting ovulation. Procedure : A specimen of cervical mucus is obtained and is spread on a clean Glass slide and allowed to dry. It is then viewed under the low power microscope. Result and interpretation : Under the influence of estrogen on Day12-Day 14 cervical mucus shows characteristic pattern of fern formation. The ferning is due to the presence of sodium chloride in the mucus secreted under estrogen effect. After ovulation on Day 21-23, ferning disappears because protein content increases and Sodium chloride decreases under the effect of progesterone. Disappearance of ferning after ovulation and if previously present its disappearance is presumptive evidence of corpus luteum activity. Also know : * Cervical mucus will show palm leaf pattern due to Estrogen. Spin barkeit of cervical mucus in a woman is maximum at ovulatory phase. Spin barkeit is demonstrated in Proliferative phase.