Objectives: Inferior vena cava compression syndrome (VCCS) is a serious complication of supine fetal magnetic resonance imaging (MRI) examinations, particularly during late gestation. This morphologic study correlated the occurrence of VCCS with the grade of inferior vena cava (IVC) compression.
Materials and methods: There were 56 fetal MRI in the supine position [median gestational weeks (GW) 27+4] and 16 fetal MRI in the lateral position (median GW 30+6) retrospectively analyzed. The grade of maternal IVC compression was determined by the maximal anterior-posterior diameter (DAP) at the level of L4/L5. Fetal head position and right-sided uterus volume were analyzed. Clinical VCCS-related symptoms during fetal MRI were assessed.
Results: A noncompressed IVC was present in 1.8% (n=1) and a DAP of 5 to <10 mm in 33.3% (n=19) and 1 to <5 mm in 64.9% (n=36). The DAP was independent of fetal head position (P=0.99) and showed no significant correlation with gestational age (r=0.33). IVC compression increased with right-sided uterus volume (r=-0.328; P=0.014). There was a significant difference in DAP in the lateral position compared with the supine position (P<0.001). Clinical assessment revealed no symptoms of VCCS in any woman.
Conclusions: The presented data support the concept of physiologic compensation for significantly reduced venous backflow in the supine position during the second and third trimesters of pregnancy.