Pregnancy is associated with an overall 5-10 fold increased risk of venous thromboembolism (VTE). VTE remains the most common cause of maternal death in the developed world. It is up to 10 times more common in pregnant women than non-pregnant women of comparable age. More than a third of pregnancy-related VTE occurs during the six weeks after delivery. When compared with vaginal delivery, cesarean delivery further increases the risk of pregnancy associated VTE by three-fold.

This is a double blind- a randomized controlled study of prophylactic LMWH in women at low risk for VTE following a cesarean section procedure. The sample size is 300 patients, Eligible, consenting, and randomized participants will receive once-daily injections of study drug (4,500 IU Tinzaparin Sodium [Innohep®] within 12- to 24-hours postpartum and continue for two weeks versus Placebo in the other arm and follow for six (6) weeks postpartum.

On the day of hospital discharge, bilateral leg imaging with compression, leg ultrasounds, and pelvic vein imaging with MRV will be completed. The primary outcome will be adjudicated, while DVT will be documented on ultrasounds or MRV on the day of hospital discharge. Secondary outcomes will include symptomatic DVT and PE, death from PE, major and minor bleeding, and HIT during the six-week postpartum period. All outcomes will be adjudicated by an independent committee of experts blinded to study drug allocation.

Inclusion Criteria:

1. Age > 18 years old.
2. Delivered by cesarean section (emergency or planned).
3. Signed, informed consent.
4. Ready access to a local health service.
5. Capable of using Tinzaparin.

Exclusion Criteria:

1. at high risk for thromboembolism (any one of the following):

   • age more than 35 years old
   • obesity (more than 80 kg)
   • parity more than 4
   • gross varicose veins
   • current infection
   • pre-eclampsia
   • immobility prior to surgery (more than 4 days)
   • Major current disease: including heart or lung disease, cancer,inflammatory bowel disease and nephrotic syndrome.
   • Extended major pelvic or abdominal surgery (e.g. cesarean hysterectomy)
   • Patients with a family history of VTE
   • History of superficial phlebitis

2. More than 36 hours since delivery

3. Need for anticoagulation, including:

   • women with a confirmed thrombophilia
   • women with paralysis of lower limbs
   • women with personal history of VTE
   • women with antiphospholipid antibody syndrome (APLA)
   • women with mechanical heart valves

4. Contraindication to heparin therapy, including history of heparin induced thrombocytopenia.

Consecutive adult patients (aged over 18 years) that had been delivered by emergency or elective cesarean section with no previous history of VTE are eligible for the study.