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
USG examination of a 28-week pregnant primigravida shows vasa pre. All of the following are true, EXCEPT: 
Select and explain. 
A. Incidence is 1:1500, B. Fetal moality rate of 20% with undiagnosed case, C. Associated with low lying placenta, D. Caesarian section is indicated
B: Fetal moality rate of 20% with undiagnosed case
Answer: B: Fetal moality rate of 20% with undiagnosed case 
Explanation: Vasa pre is a condition in which fetal vessels traverse the membranes in the lower uterine segment, crossing over the cervical os on front of the fetal head. Vasa pre complicates approximately 1 in 1000 to 1 in 5000 pregnancies. Perinatal moality ranges from 30% to 100%. The appropriate course of action is to deliver immediately caesarean section to prevent impending fetal demise. Ref: Wagner S.A. (2013). Chapter 18. Third-Trimester Vaginal Bleeding. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.