Pulmonary embolism

Pulmonary embolism is about 5 times more common in pregnant women than in similarly aged nonpregnant women, but is still relatively infrequent (about 0.1% of pregnancies). The increased risk is related to changes in coagulation factors related to pregnancy, to local obstruction of veins by the uterus, and trauma to veins during delivery.

Diagnosis of a DVT can be made by ultrasound, and will require similar treatment to a pulmonary embolism. Both ventilation-perfusion (V/Q) scans and CT angiograms are used in pregnancy to diagnose pulmonary embolism, the latter being more common. V/Q is useful in the woman with a allergy to intravenous contrast. Radiation risk to the fetus from CT angiogram is minimal, with appropriate precautions and screening of the abdomen. V/Q scan radiation exposure can be reduced by beginning with a perfusion scan using half the dose (and avoiding the ventilation component if this is normal)


Treatment is with low molecular weight heparin (LMWH), preferably using a weight-adjusted dosing regimen, and/or titrating to anti-factor X levels. Treatment should be for a minumum of 3 months, and for at least 6 weeks postpartum. LMWH should be held for 24 hr prior to delivery or epidural/spinal anesthesia. Warfarin is not used during pregnancy, but is safe during lactation. Thrombolytic therapy has been used in pregnancy, when clinically indicated.


Miller MA, Chalhoub M, Bourjeily G. Peripartum pulmonary embolism. Clin Chest Med. 32(1):147-64, 2011

Scarsbrook AF, Gleeson FV. Investigating suspected pulmonary embolism in pregnancy. BMJ. 2007;334:418-9.

Ginsberg JS, Greer I, Hirsh J: Use of antithrombotic agents during pregnancy. Chest 119(Suppl 1):122S–131S, 2001.

Bates SM, Greer IA, Middeldorp S, Veenstra DL, Prabulos A-M, Vandvik PO. 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. 141(2_suppl):e691S-e736S, 2012

Special Pregnancy Program

Referrals »

Fetal Medicine: 416-586-4800 x 7756
Fax: 416-586-3216

Maternal Medicine: 416-586-4800 x 7000
Fax: 416-586-5109

Main clinic hours: Monday to Friday, 8am to 4pm

Prenatal Diagnosis & Medical Genetics

Referrals »

phone: 416-586-4800 x 4523
fax numbers:
416-586-4723 or 416-586-8384

Perinatal Mental Health

Referrals »

Phone: 416-586-4800 x 8325
Fax: 416-586-8596