**Question:** Cervical cerclage is advised in an antenatal woman with a prior preterm birth if the cervical length measures

A. 25 mm
B. 15 mm
C. 10 mm
D. 5 mm

**Core Concept:** Cervical cerclage is a medical procedure used to strengthen the cervix in high-risk pregnant women to prevent preterm birth. Cervical length measurement is an important factor in determining the need for cerclage placement.

**Why the Correct Answer is Right:** Cervical cerclage is recommended when the cervical length is shortened to a critical level, as it increases the risk of preterm labor and delivery. The correct answer, D (5 mm), is the threshold at which cerclage placement is considered necessary, as a shortened cervical length below 5 mm is associated with a high risk of preterm birth.

**Why Each Wrong Option is Incorrect:**

A (25 mm): A cervical length of 25 mm is considered normal and does not warrant cerclage placement.

B (15 mm): Although shorter than the correct answer, a length of 15 mm is still within a normal range and does not require cerclage placement.

C (10 mm): While shorter than the correct answer, a cervical length of 10 mm is considered borderline and may indicate a higher risk for preterm birth, but still not as high as a length of 5 mm, which is considered a critical threshold.

**Clinical Pearl:** Regular cervical length assessment, particularly in women with a history of preterm birth, is crucial for identifying those who may benefit from cerclage placement to prevent preterm labor and improve pregnancy outcomes. Early detection and intervention can reduce the risk of preterm birth and associated neonatal morbidity and mortality.

**Correct Answer:** D (5 mm)

**Why the Correct Answer is Right:** A cervical length measurement of 5 mm is indicative of a short cervix and a higher risk for preterm labor. In such cases, cerclage placement can be considered to strengthen the cervix and prevent preterm birth.

**Why Each Wrong Option is Incorrect:**

A (25 mm): A cervical length of 25 mm is considered normal and does not indicate a high risk for preterm labor. Cerclage placement is not necessary in this scenario.

B (15 mm): While a length of 15 mm is shorter than the normal range (25 mm), it still represents a cervix of average length and does not warrant cerclage placement.

C (10 mm): A cervical length of 10 mm is considered borderline and may indicate a higher risk for preterm labor compared to a normal length, but still not as high as a length of 5 mm, which is the critical threshold for cerclage placement.