This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Gynae), Subject name: Gynaecology & Obstetrics
Most common cause of rupture uterus? 
Select and explain. 
A. Separation of previous caesarean scar, B. Internal version, C. Excess dosage of oxytocin, D. Complicated manual removal of placenta
A: Separation of previous caesarean scar
Answer: A: Separation of previous caesarean scar 
Explanation: Ans. a (Separation of previous caesarean scar) (Ref. Dutta obst. 6th ed460)RUPTURE UTERUSDefinition: Dissolution in the continuity of uterine wall anytime beyond 28 weeks of pregnancy.Etiology# Spontaneous rupture during pregnancy: Complete and involves upper segment of uterus. Obstructive rupture during labour: Involves lower segment.# Non-obstructive rupture during labour: Complete and involves fundus.# Incidence of scar rupture is 1-2 % in lower segment scar and 5-10 times more in classical scar.# Obstructive rupture which is an end result of obstructed labour due to neglect in intranatal care involves lower segment and usually extends through one lateral side of uterus to the upper segment. Additionally, oxytocin should not be used in women with prior classic cesarean section scars because the risk of uterine rupture is high (5%-10%).Features of Uterine rupture (during labour)a) Failure in progress of labour.b) Suprapubic pain.c) Slight bleeding PV and Hematuria.d) Alteration in fetal heart rate.e) Unexplained maternal tachycardia.f) Hypotension.g) Tenderness over scar.h) Bladder tenesmus.i) Ballooning of lower segment