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
On Transvaginal Sonography (TVS) which of the following shapes of cervix indicate imminent preterm labour? 
Select and explain. 
A. T, B. Y, C. U, D. O
C: U
Answer: C: U 
Explanation: On ultrasound examination, normal cervix is T shaped. As the internal cervical os opens and the membrane stas herniating to the upper pa of endocervical canal, the cervical shape on ultrasound changes to a Y. With fuher progression of cervical changes, Y shape changes to V and ultimately to U. Thus, U shaped cervix on transvaginal sonography indicate imminent preterm labour. Ref: Textbook of Obstetrics By D. C Dutta, 6th Edition, Page 315; SOAP For Obstetrics And Gynecology By Peter S. Uzelac Page 50; Tips and Tricks in Operative Obstetrics and Gynecology By Richa Saxena Page 221.