This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abnormal labor, Subject name: Gynaecology & Obstetrics
Cut off value of length of cervix at 24 weeks of gestation for prediction of preterm delivery is 
Select and explain. 
A. 0.5 cm, B. 1.5 cm, C. 2.5 cm, D. 3.5 cm
C: 2.5 cm
Answer: C: 2.5 cm 
Explanation: Diagnosis of preterm labor : Regular uterine contractions with or without pain Dilatation more than 2cm and 80% effacement of cervix Length of the cervix <2.5 cm and funnelling of internal os Pelvic pressure, backache ,vaginal discharge Ref: Dutta Obs 9e pg 294.