This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Cervical cerclage is advised in an antenatal woman with a prior preterm bih if the cervical length measures \nSelect and explain. \nA. Not related to cervical length, B. Between 3-4 cm, C. Between 2.5 to 2.9 cm, D. < 2.5 cm', 'role': 'user'}, {'content': "Answer: D \nExplanation: Cervical length screening is now recommended by both the American College of Obstetricians and Gynecologists (2016b) and the Society for Maternal-Fetal Medicine (2015) for women with prior preterm bih.Between 16 and 24 weeks' gestation, sonographic cervical measurement is completed every 2 weeks.If an initial or subsequent cervical length is 25 to 29 mm, then a weekly interval is considered.If the cervical length measures <25 mm, cerclage is offered to this group of women. Notably, for women without history of preterm bih but with a sho cervix incidentally identified sonographically, progesterone therapy is offered instead of cerclage.Reference: William's Obstetrics; 25th edition; Chapter 18; Aboion", 'role': 'assistant'}]