**Question:** On TVS which of the following shape of cervix indicates preterm labour:

A. Round
B. Irregular
C. Oblate
D. Pear-shaped

**Core Concept:**
Understanding the normal and abnormal cervical shapes on transvaginal ultrasound (TVS) is crucial in diagnosing preterm labour. The cervix undergoes changes during pregnancy, including dilation and shortening. In normal pregnancy, the cervix appears oval or pear-shaped.

**Why the Correct Answer is Right:**
In preterm labour, the cervix becomes shorter and more dilated than in a normal pregnancy. The correct answer, "Pear-shaped," reflects this change in cervical shape, as it represents a shortened and dilated cervix.

**Why Each Wrong Option is Incorrect:**
A. Round: A round-shaped cervix indicates a non-dilated and non-shortened cervix, which is not indicative of preterm labour.
B. Irregular: Although an irregular shape might be seen in preterm labour, the pear-shaped option more accurately represents the shortened and dilated condition.
C. Oblate: An oblate shape is associated with a non-dilated cervix and is less likely to be seen in preterm labour.

**Clinical Pearl:**

The pear-shaped cervical appearance on TVS is important to recognize, as it can be an early sign of preterm labour. Understanding these changes can lead to timely interventions to prevent preterm births and improve maternal and neonatal outcomes.

**Correct Answer:** D. Pear-shaped