This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Second stage of labor begins with 
Select and explain. 
A. Fully effaced cervix, B. Fully dilated cervix, C. Fetal delivery, D. Placental delivery
B: Fully dilated cervix
Answer: B: Fully dilated cervix 
Explanation: Second Stage of LaborThis stage begins with complete cervical dilation and ends with fetal delivery. The median duration is approximately 50 minutes for nulliparas and about 20 minutes for multiparas, but it is highly variable Reference: William's Obstetrics; 25th edition; Chapter 22; Normal Labor