Prevention & Treatment of DVT/PE in Pregnant Women
from the ACCP Guidelines, 9th Ed.
The ACCP’s recommendation classification system:
- 1 = “recommendation”
- 2 = “suggestion”
- A = based on strong evidence from randomized trials
- B = moderate evidence that may include randomized trials or observational studies
- C = weak evidence, mostly consensus opinion
Low-Molecular Weight Heparin (Not Warfarin) Preferred In Pregnancy
As most physicians hopefully know, warfarin is teratogenic (causes birth defects and miscarriages). For prevention and/or treatment of deep venous thrombosis (DVT) and pulmonary embolism (PE) in pregnant women, the ACCP recommends low-molecular weight heparin instead of warfarin/Coumadin (Grade 1B).
The one exception I see here is for pregnant women with mechanical heart valves, for whom the ACCP considers warfarin to be acceptable as an alternative to heparin in certain situations (see below).
For Women Taking Coumadin Who Are Trying to Become Pregnant
The ACCP suggests a woman taking warfarin/Coumadin who is trying to conceive a pregnancy should take frequent pregnancy tests and switch from warfarin to low molecular weight heparin (LMWH) after becoming pregnant — as opposed to switching from warfarin to LMWH while trying to conceive (Grade 2C).
This (Grade 2C) is the softest possible recommendation/suggestion; ACCP further clarifies that women who prefer the inconvenience, risks, and expense of heparin injections over the risk of miscarriage and birth defects (i.e., most women I know) are welcome to switch to low molecular weight heparin while trying to conceive a healthy child.
(Is this guy even an obstetrician?)
After Cesareans, Most Women Don’t Need Special DVT/PE Prophlyaxis
Women who have just undergone caesarean section who are at average risk for DVT/PE (i.e., the vast majority of women) should not receive DVT/PE prophylaxis, other than getting out of bed to walk early and often (Grade 1B).
Women considered to be at increased risk for DVT/PE after cesarean section are suggested to receive prophylaxis with low molecular weight heparin, or (for those with a contraindication to anticoagulation) elastic stockings or intermittent pneumatic leg compression devices while in the hospital (Grade 2B). Women are at increased risk for DVT/PE after cesarean section, ACCP says, are those with one major risk factor or 2 minor risk factors for DVT/PE:
|Risk for Postpartum DVT/PE (After Delivery)|
|Major Risk Factors (Need 1)||Minor Risk Factors (Need 2)|
|Strict bed rest > 1 week before delivery||Protein C or S deficiency|
|Previous DVT or PE||Smoking 10+ cigs/day|
|Preeclampsia + restricted fetal growth||Preeclampsia|
|Lupus, heart disease, or sickle cell dz||Slow fetal growth|
|Factor V Leiden (homo- or heterozyg.)||Bleeding after delivery > 1L|
|Prothrombin mutation (homo- or hetero-)||Multiples (twins, triplets)|
|Infection after delivery|
|Bleeding > 1L after delivery, requiring surgery|
For Pregnant Women With Acute DVT or PE, LMWH is Advised
For pregnant women with acute DVT or PE, the ACCP recommends that low-molecular weight heparin be given rather than unfractionated heparin (Grade 1B), and continued during pregnancy for as long as it is indicated, rather than transitioning to warfarin/Coumadin (Grade 1A).
The ACCP recommends that for pregnant women with acute DVT or PE, LMWH be stopped at least 24 hours before inducing labor, placing an epidural, or performing a cesarean section (Grade 1B). They suggest that pregnant women’s treatment for DVT or PE be extended for 6 weeks after delivery (Grade 2C).
Consider Prophlyaxis Before, After Delivery for Some Pregnant Women
Pregnant Women With Past DVT/PE
For all women with a remote history of DVT or PE, ACCP suggests providing prophylactic/intermediate dosing of LMWH or warfarin/Coumadin (to INR 2-3) for 6 weeks after delivery (Grade 2B). (Intermediate dosing for enoxaparin/Lovenox is generally 40 mg SC qday).
ACCP suggests women with prior DVT or PE and a moderate/high recurrence risk should consider taking prophylactic or intermediate-dose LMWH during pregnancy (Grade 2C). This includes women with a prior DVT or PE that was unprovoked, or related to pregnancy or estrogen use.
Pregnant women with prior DVT/PE at low risk for recurrence (because their VTE was provoked by a transient risk factor unrelated to pregnancy or estrogen use) and their doctors should watch carefully for signs or symptoms of DVT or PE during pregnancy, but ACCP suggests they not use LMWH as prophylaxis (Grade 2C).
In the text, authors advise against screening pregnant women with prior DVT/PE for recurrent DVT with serial compression ultrasounds of the legs, because of the high risk for false positives (not graded). An exception might be if there is a baseline ultrasound of the previously DVT-affected leg, to compare new studies against.
Pregnant Women With Known Thrombophilia
For pregnant women who are homozygous for the factor V Leiden or prothrombin 20210A mutation (who have never had a DVT or PE):
- For those these homozygous mutations AND a family history of DVT or PE, ACCP suggests the use of LMWH prophylactic or intermediate doses during pregnancy and for 6 weeks after delivery (with warfarin an alternative after delivery) (Grade 2B).
- For those with these homozygous mutations but NO family history or personal history of DVT/PE, ACCP suggests watchful vigilance during pregnancy (no LMWH) and prophylactic or intermediate dose LMWH for 6 weeks after delivery (Grade 2B).
For pregnant women with other thrombophilias, and no personal history of DVT/PE:
- Those with a family history of DVT/PE should be vigilant during pregnancy with their doctors, and consider LMWH in prophylactic or intermediate dosing after delivery (alternatively warfarin to INR 2-3, if protein C or S deficiency is not present) (Grade 2C)
- Those with no family history of DVT/PE should rely with their doctors on clinical vigilance during pregnancy and after delivery; LMWH is not suggested (Grade 2C).
Pregnant Women With Mechanical Heart Valves
For pregnant women with mechanical heart valves, ACCP considers any of the following anticoagulation options to be reasonable, and that this decision is completely dependent on individual values and preferences:
- Low-molecular weight heparin in therapeutic doses throughout pregnancy (dosed to achieve peak anti-Xa levels);
- Unfractionated heparin subcutaneously b.i.d. in therapeutic doses throughout pregnancy (dosed to aPTT >2x normal or anti-Xa levels 0.35 to 0.70);
- Heparin (either of the above) until the 13th week, then warfarin/Coumadin until near the time of delivery, then resume heparin.
Pregnant women with mechanical valves at very high risk for thromboembolism — such as those with a past history of clot while using anticoagulation, or who have an older generation prosthetic mitral valve — in whom heparin might not be considered sufficient anticoagulation — may consider warfarin throughout pregnancy rather than heparin (Grade 2C). This extremely tough choice weighs the risk of catastrophic stroke over the risk of fetal abnormalities or miscarriage, and is of course dependent on the mother’s values and preferences.
More DVT/PE Recommendations for Pregnant Women
ACCP recommends women who are pregnant or breastfeeding not take the newer generation anticoagulants dabigatran (Pradaxa), rivaroxaban (Xarelto) and apixaban (Grade 1C).
For women who are breastfeeding, ACCP recommends continuing warfarin, unfractionated heparin, or acenocoumarol, for women who are taking these drugs (Grade 1A), as well as low molecular weight heparin, danaparoid, or r-hirudin (Grade 1B) and low dose aspirin (Grade 2C). ACCP suggests breastfeeding women use other agents besides fondaparinux (Grade 2C).
ACCP suggests pregnant women not use fondaparinux or IV/SC direct thrombin inhibitors, unless they have severe heparin induced thrombocytopenia and cannot take danaparoid (Grade 2C).
This summary includes nearly all, but not all of the ACCP’s 9th edition guidelines and Chest recommendations for treatment and prevention of DVT/PE in pregnant women. Please refer to the original document for the most complete listing.
Bates SM et al. VTE, Thrombophilia, Antithrombotic Therapy, and Pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012;141 no 2 suppl:e691S-3736S.