Deep vein thrombosis (DVT) in pregnant patients is more likely to occur on the left side, and in particular in the left leg, write the authors of a Review article in CMAJ (Canadian Medical Association Journal) (pre-embargo link only) http://www.cmaj.ca/embargo/cmaj091692.pdf.
"In nonpregnant patients, DVT, the formation of a blood clot, is most common in the calf veins," write Dr. Wee-Shian Chan, Women's College Hospital and coauthors. "This review was conducted to see whether this is also the case for pregnant women in order to limit diagnostic procedures, such as x-rays, because of the effects on the fetus."
The authors reviewed 1098 papers, and found only six that met the inclusion criteria. Despite, the limited number of studies on this area it has been found that left-sided DVT and proximal DVT are common in pregnancy.
The authors conclude that until prospective diagnostic studies are available for pregnant patients, it may be prudent to conduct a routine examination of the iliofemoral system when a pregnant patient presents with suspected deep vein thrombosis.
In a related commentary http://www.cmaj.ca/embargo/cmaj100279.pdf, Dr. Ristaa Kajaa, Professor of Medicine, Turku University, Satakunta Central Hospital, writes that despite the limited number of pertinent studies presenting data in this area, the results of this study suggest that the anatomic distribution of deep vein thrombosis in pregnant women may differ from nonpregnant patients. The increased prevalence of isolated proximal vein DVT seen in this study is clinically important because of the high risk of pulmonary embolism.
Canadian Medical Association Journal