Determination of fetal body volume measurement at term with magnetic resonance imaging: effect of various factors.

Purpose: To evaluate various factors that potentially influence the fetal body volume (FBV) measurement using magnetic resonance imaging (MRI) and to analyze whether the technique of measurement could be simplified.

Materials And Methods: In 20 singleton pregnancies scheduled for a planned delivery, FBV measurements were performed by two independent operators on sagittal, axial and coronal planes and with various slice thickness and intersection gap, totalizing 100 examinations. MR estimation of fetal weight (MR-EFW) was calculated based on the equation developed by Baker. The relative error of MR-EFW was calculated in function of birth weight (BW). Regression analysis was used to investigate the effect on the relative error of MR-EFW of different variables but also to investigate the effect on the measurement time of the FBV of various factors.

Results: The mean relative error of MR-EFW was 1.96% and was significantly associated only with patient's BMI but not with the type of MR sequence used or other variables. Type of MR sequence used and BW were significantly associated with the measurement time of FBV.

Conclusion: Using MRI, the time for FBV measurement can be significantly reduced using thicker slices or intersection gap, with similar accuracy.