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
[{'content': 'All are risk factors for preterm delivery except \nSelect and explain. \nA. Absence of fetal fibronectin at < 37 weeks, B. Previous history of preterm baby, C. Asymptomatic cervical dilatation, D. Chylamydial infection of genital tract', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Fetal fibronectin is a fetal glycoprotein that is expressed in the first half of pregnancy. After 20 weeks it is not normally detectable until membranes rupture. So its absence has been associated with a low risk of preterm delivery,whereas other 3 are obvious risk factors for preterm labour. (TB of OBG Sheila 2nd edtn pg 192,193)', 'role': 'assistant'}]