Heparin Use in Pregnancy

Contributor: John V. Dacus, MD and Shelley Chapman, MD                                                                                                                                 
Last Update: 2/14/2020

There is no consensus in the literature concerning which heparin (unfractionated or low molecular weight heparin) and which dosing regimen is best during pregnancy.  The following are guidelines accepted by the Maternal-Fetal Medicine Division.  There may be exceptions to these such as the inability of the patient to pay for Lovenox, or Dalteparin, or the patient developing an allergy to one of the heparins, or the presence of renal failure.

Prophylaxis regimen during pregnancy

• Unfractionated heparin
  5,000 u subcutaneous q 12 hours during first trimester
  7,500 u subcutaneous q 12 hours during second trimester
  10,000 u subcutaneous q 12 hours during third trimester (Check APTT or antifactor Xa level once in 7 days)
• Lovenox
  40 mg subcutaneous q 12 hours OR 40 mg subcutaneous daily
  0.5 mg/kg q 12 hours
• Dalteparin
  5,000 u subcutaneous q 12 hours
• All patients will receive calcium 1500 – 2000 mg daily and a prenatal vitamin containing vitamin D.
• Check platelet count initially and then in 7-14 days.

 

Therapeutic regimen during pregnancy

• Lovenox 1.0 mg/kg subcutaneous q 12 hours.  Achieve anti factor Xa serum level of 0.5 to 1.2 u/ml four hours post injection.
• Dalteparin 100u/kg subcutaneous q 12 hours.  Achieve anti factor Xa serum level of 0.5 to 1.2 u/ml four hours post injection.
• Alternatively unfractionated heparin.  Begin 10,000 to 15,000 u subcutaneous q 12 hours.  Titrate to achieve antifactor Xa of 0.3 to 0.7 u/ml 6 hours post injection or APTT 1.5 to 2 times control 6 hours post injection.
• All patients should receive additional calcium and vitamin D, as above.
• Check platelet count initially and then in 7-14 days.

 

Switching from Lovenox or Dalteparin to unfractionated heparin at 36 weeks

• Prophylactic
  Stop Lovenox  or Dalteparin for 12 hours and begin unfractionated heparin at 10,000 u q 12 hours.
  Check APTT or antifactor Xa level once in 7 days.
• Therapeutic
  Stop Lovenox or Dalteparin  for 12 hours.
  Begin unfractionated heparin at 333 u/kg subcutaneous and then 250 u/kg  subcutaneous q 12 hours.
  Monitor APTT initially and then after second maintenance dose to achieve a value 1½ – 2½ times control 6 hours post injection or anti factor Xa level 0.3 – 0.7 u/ml 6 hours after AM dose.

 

Intrapartum anticoagulation

• Stop Heparin if PROM or labor occurs
• SCD’s during labor or C/S
• Start prophylactic or therapeutic heparin (usually Lovenox/ Dalteparin) after delivery
  12 hours s/p Vaginal Delivery
  24 hours s/p C/S

 

Postpartum anticoagulation

• Prophylaxis: Unfractionated Heparin 10,000 units SQ every 12 hours
  Lovenox 40 mg SQ every 12 hours OR Lovenox 40 mg SQ daily
• Therapeutic: Patient can elect to use Coumadin or Heparin x 6 weeks
  Lovenox, Dalteparin or unfractionated Heparin – continue appropriate dosage. Bridge Coumadin starts with Heparin in hospital.
  Coumadin (may be used even in breast feeding)

1. Start therapeutic Lovenox or Dalteparin
2. Give oral Coumadin ONLY after giving Lovenox or Dalteparin
   **IF COUMADIN IS GIVEN WITHOUT HEPARIN ALREADY GIVEN, (THERE ARE LOWER PROTEIN C AND PROTEIN S LEVELS IN THE PATIENT) IT WILL INCREASE THE RISK OF THROMBOEMBOLISM!**
3. Continue Lovenox or Dalteparin until INR ≥2.0 on 2 consecutive days, then discontinue Lovenox or Dalteparin
4. Continue Coumadin for 6 weeks. May follow up for labs at primary care doctor, Coumadin clinic or obstetrician’s office.