The anatomic distribution of
vein thromboses differed among pregnant and nonpregnant women, findings
from a meta-analysis suggested, and pregnant women were more likely to
experience left-sided deep vein thrombosis.
Although results of observational studies have suggested this link
before, little remains known about the anatomic distribution of DVT in pregnant
women because of the risks involved with exposing the fetus to radiation or
contrasting agents necessary for noninvasive imaging studies.
Researchers analyzed six studies involving 124 pregnant women and
abstracted data concerning the side of the thrombosis; the anatomic
distribution of the thrombosis; and the involvement of each venous segment at
the time of DVT diagnoses. Eligible studies consisted of case series or
observational cohorts that involved three or more participants in which DVT was
diagnosed using compression ultrasonography, MRI, CT or venography.
The researchers found that 84 of 96 patients (88%) for which the
affected side was known experienced left-leg involvement and that 87 of the 122
thromboses (71%) were restricted to the proximal veins without calf-vein
involvement. Furthermore, among cases of proximal thromboses, 56 of 87 cases
(64%) occurred in the
iliac and/or femoral vein.
These observations strongly suggest that the anatomic distribution
of DVT in pregnant women, and perhaps the pathophysiology of the condition, may
indeed differ from that reported in the general population, the
Data from previous studies involving nonpregnant patients indicated that
proximal thrombosis involving calf veins was common (58% to 87%), whereas
isolated proximal vein thrombi were uncommon (0% to 13%).
We might speculate that among pregnant women, a
May-Thurnerlike syndrome brought on by compression of the left iliac vein
by the gravid uterus
plays a major role in the increased incidence of
iliofemoral DVT in late pregnancy, the researchers wrote, but noted that
DVT frequency among pregnant women was equal during all three trimesters.
Until prospective diagnostic studies are available for pregnant patients,
it may be prudent to conduct a routine examination of the iliofemoral venous
system when a pregnant patient presents with suspected DVT.
Chan W-S. CMAJ. 2010;doi:10.1503/cmaj.091692.