Correlation of measured amnionic fluid volume to sonographic and magnetic resonance predictions.

OBJECTIVE: The purpose of this study was to compare the relationship between the actual amnionic fluid volume that was measured at delivery and magnetic resonance amnionic fluid volume determination, largest vertical pocket, and amnionic fluid index. STUDY DESIGN: Three hours before cesarean delivery, 80 women had sonographic measurement of the amnionic fluid index and the largest vertical pocket. Magnetic resonance imaging was then completed, and the magnetic resonance amnionic fluid volume was determined. At surgery, the amnionic fluid was collected. Pearson correlations were determined. Receiver operating characteristic curves were developed for each method as a measure of predictability for oligohydramnios. RESULTS: The correlations for the magnetic resonance amnionic fluid volume, amnionic fluid index, and largest vertical pocket to amnionic fluid volume was 0.84, 0.77, and 0.71, respectively. Magnetic resonance amnionic fluid volume has a statistically higher correlation than the largest vertical pocket ( P = .046). The 3 methods, however, are statistically comparable for identifying oligohydramnios. CONCLUSION: Magnetic resonance imaging is comparable with ultrasound evaluation for the prediction of oligohydramnios. Correlations to actual amnionic fluid volume are also comparable.

Comparison of magnetic resonance imaging to ultrasound in the estimation of birth weight at term.

OBJECTIVE: This study was undertaken to compare magnetic resonance (MR) and ultrasound (US) fetal weight estimates obtained immediately before delivery with birth weight. STUDY DESIGN: Eighty women scheduled for a cesarean delivery underwent a fast acquisition MR and US for fetal weight estimation within 3 hours of delivery. Prospective MR calculation was based on the equation 0.12+1.031 g/mLxfetal volume (mL)=MR weight (g). US fetal weight estimation was calculated by the formula by Hadlock et al. Estimations were compared with birth weight. RESULTS: Correlation (95% CI) between birth weight and MR weight is 0.95 with a mean absolute error of 129 g (105-155) compared with the correlation between birth weight and US of 0.85 with a mean absolute error of 225 g (186-264). The correlation for birth weight and MR imaging is significantly greater than that of birth weight and US, P<.001. CONCLUSION: Birth weight estimation is more accurate by MR imaging than by US in term infants.

Fetal central nervous system biometry on MR imaging.

OBJECTIVE: We sought to compare the biometry of the fetal head on MR imaging with sonographic measurements in fetuses with and without suspected central nervous system abnormalities. MATERIALS AND METHODS: Blinded retrospective measurements of biparietal diameter, head circumference, and cerebellar width obtained on MR imaging were assigned a gestational age on the basis of median sonographic measurements and compared with sonographic and clinical assignment of gestational age in fetuses with no central nervous system abnormalities. In fetuses with central nervous system abnormalities, the same MR measurements were compared with sonographic measurements obtained within 1 week. Single-shot fast spin-echo sequences were obtained. Pearson's product moment correlation coefficients and paired sample t tests were performed. RESULTS: In 22 fetuses with no suspected central nervous system abnormalities, significant correlation was seen in the assignment of gestational age by MR measurements and sonographic gestational age. In 25 fetuses with central nervous system abnormalities, significant correlation was also seen between biparietal diameter and head circumference measurements. The mean biparietal diameter on MR imaging was greater than on sonography in those fetuses with central nervous system abnormalities (p = 0.038). CONCLUSION: MR imaging measurements of biparietal diameter, head circumference, and cerebellar width are strongly correlated to gestational age in fetuses without central nervous system abnormalities. Significant correlation is found between MR imaging and sonographic measurements of biparietal diameter and head circumference in fetuses with central nervous system abnormalities. Larger biparietal diameter measurements were seen with MR imaging than with sonography in the abnormal group. Fetal central nervous system biometry can be performed as part of the MR imaging evaluation of the fetal central nervous system.