The average level of blood thinning, resulting from an individual weight determined dose of Clexane, when given to women after caesarian section to prevent blood clots.

Following major surgery patients are at increased risk of developing blood clots in the veins of the lower limb and in some patients these may dislodge, travel to the lung as pulmonary emboli, resulting in breathing difficulties and rarely death. The situation is no different after caesarian section, where patients are at increased risk of blood clots, however the risk is not the same for all but influenced by factors such as previous history of blood clots, the need for emergency surgery, age and body weight. After your surgery we can minimize the risk of blood clots by mobilizing you as soon as possible, using below knee compression stockings, which prevent pooling of blood in calf veins and in certain patients by once daily injections under the skin of a blood thinning low molecular weight heparin drug (LMWH) called enoxaparin. For many years the dose of enoxaparin has been fixed and not adjusted for body weight, however there is evidence from studies in overweight non-pregnant patients that as body weight increases an increase in dose is required to maintain prevention. Pregnancy also alters the way these enoxaparin is handled by the body resulting in an increase in the dose required (at the end of pregnancy and immediately after delivery) to provide the same action as in the non-pregnant patient. Recently, the Royal College of Obstetrician and Gynaecologists (RCOG) in the United Kingdom have updated their guidelines for prevention of thrombosis after caesarian section and recommend that patients classified as intermediate risk or greater should be given LMWH with the dose determined by their actual body weight at 8 -16 weeks of gestation (usually referred to as the booking weight). We believe that you fall into the intermediate (or high) risk category and therefore would benefit from having LMWH preventative treatment. The dose given to you will be that recommended by the RCOG guideline and will be calculated based on your body weight at the time of registering for care at the Mercy Hospital for Women. For patients of less than 90 kg you will receive what for many years has been the standard dose of enoxaparin. For patients above 90 kg you will receive a dose greater than this fixed dose, which we believe is safe and is likely to result in better prevention of clots compared to the usual dose. We are asking that you consent to having three samples of blood (10 mls each) taken and analyzed for LMWH blood thinning activity (antiXa levels). The first and second samples will be taken immediately prior to & then four hours after your first preventative injection some 4-12 hours after completion of your caesarian section. A third sample will be taken four hours after your third or fourth dose given on the day prior to your discharge from hospital. An additional small plastic cannula will be inserted into a arm vein at the time of your caesarian section and the first blood sample taken at that time. A second sample, hopefully via the cannula, will be taken 3 – 5 hours after the injection of Enoxaparin some 4-12 hours after your caesarian delivery. The third sample will require a separate blood test to be taken. The study does not change the obstetric or anaesthetic management of your delivery. Breast feeding is considered safe whilst on enoxaparin. All blood thinners lead to a slightly increased risk of wound and uterine bleeding. We don't believe that the risk of bleeding is increased over that seen in non pregnant patients given enoxaparin to prevent blood clots following surgery.