Cut-off value of cervical length at 24 weeks of gestation for prediction of preterm delivery is:
**Core Concept**
The cervical length is a crucial predictor of preterm delivery in pregnant women. The measurement of cervical length is typically performed between 16 and 24 weeks of gestation using transvaginal ultrasound. A shorter cervical length is associated with an increased risk of preterm labor.
**Why the Correct Answer is Right**
A cervical length of ≤ 25 mm at 24 weeks of gestation is considered the cut-off value for predicting preterm delivery. This is because a cervical length of ≤ 25 mm is associated with a higher risk of spontaneous preterm birth. The cervix is considered "short" if it measures ≤ 25 mm, indicating a higher risk of cervical insufficiency and subsequent preterm labor.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because there is no widely accepted cut-off value for cervical length at 24 weeks of gestation. A cut-off value of ≤ 20 mm may be too strict and may not accurately predict preterm delivery.
* **Option B:** This option is incorrect because a cut-off value of ≥ 30 mm may not accurately predict preterm delivery. Women with a cervical length of ≥ 30 mm may still be at risk for preterm labor.
* **Option C:** This option is incorrect because a cut-off value of ≤ 15 mm is too strict and may not accurately predict preterm delivery. Women with a cervical length of ≤ 15 mm may be at higher risk for preterm labor, but a cut-off value of ≤ 25 mm is more widely accepted.
**Clinical Pearl / High-Yield Fact**
A cervical length of ≤ 25 mm at 24 weeks of gestation is a significant predictor of preterm delivery, and women with this measurement should be closely monitored for signs of preterm labor.
**Correct Answer: B. 25 mm**