This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Supine hypotension is a characteristic feature of: 
Select and explain. 
A. First trimester of pregnancy, B. 2nd trimester of pregnancy, C. 3rd trimester of pregnancy, D. Twin pregnancy
C: 3rd trimester of pregnancy
Answer: C: 3rd trimester of pregnancy 
Explanation: Supine Hypotension syndrome: During late pregnancy, the gravid uterus produces a compression effect on the inferior vena cava when the patient is in supine position. This however results in the opening up of the collateral circulation by means of paraveebral and azygos veins. In some cases when collateral circulation fails to open up, the venous return to the hea may be seriously cuailed. This results in production of hypotension, tachycardia and syncope. Note: The normal blood pressure is quickly restored by turning the patient to lateral position. The augmentation of the venous return during uterine contraction prevents the manifestation from developing during labour. Ref: Textbook of Obstetrics D.C.Dutta 6th Ed Page 53.