<prompt> All of the following are risk factors for deep vein thrombosis DVT except:ObesityAge less than 40 yearsDuration of surgery more than thiy minutesUse of the oestrogen-progesterone contraceptive pills  <response>: Patients over the age of 40 years is a risk factor for DVT. High dose estrogen therapy is also associated with DVT. Ref: Bailey and Loves Sho Practice of Surgery, 24th Edition, Page 970. 