Caroline Kadji

Fetal Weight Estimation: Comparison of Two-dimensional US and MR Imaging Assessments

PURPOSE To prospectively define fetal density in the second half of pregnancy by using magnetic resonance (MR) imaging and to compare estimates of fetal weight based on ultrasonography (US) and MR imaging with actual birth weight. MATERIALS AND METHODS Written informed consent was obtained for this ethics committee-approved study. In this cross-sectional study between March 2011 and May 2012, fetal density was calculated as actual birth weight at delivery divided by fetal body volume at MR imaging in 188 fetuses between 20 weeks and 2 days and 42 weeks and 1 day of gestational age. Regression analysis was used to investigate the effect of variables, including sex, on fetal density. The US estimate of fetal weight was performed according to Hadlock et al, and the MR estimate of fetal weight was calculated based on the equation developed by Baker et al. US and MR estimates of fetal weight were compared with actual birth weights by using regression analysis. RESULTS Median fetal density was equal to 1.04 (range, 0.95-1.18). Fetal density was significantly associated with gestational age at delivery but not with fetal sex. In 26.6% of fetuses, the US estimate of fetal weight had a relative error of more than 10%, while a similar relative error for the MR estimate of fetal weight occurred in only 1.1% of fetuses. The limits of agreement were narrower with the MR estimate of fetal weight compared with the US estimate of fetal weight. CONCLUSION In the second half of pregnancy, fetal density varies with gestational age. Fetal weight estimates by using fetal MR imaging are better than those by using prenatal US.

The Use of a Software-Assisted Method to Estimate Fetal Weight at and Near Term Using Magnetic Resonance Imaging

Objective: The aim of this study was to apply a semi-automated calculation method of fetal body volume and, thus, of magnetic resonance-estimated fetal weight (MR-EFW) prior to planned delivery and to evaluate whether the technique of measurement could be simplified while remaining accurate. Methods: MR-EFW was calculated using a semi-automated method at 38.6 weeks of gestation in 36 patients and compared to the picture archiving and communication system (PACS). Per patient, 8 sequences were acquired with a slice thickness of 4-8 mm and an intersection gap of 0, 4, 8, 12, 16, or 20 mm. The median absolute relative errors for MR-EFW and the time of planimetric measurements were calculated for all 8 sequences and for each method (assisted vs. PACS), and the difference between the methods was calculated. Results: The median delivery weight was 3,280 g. The overall median relative error for all 288 MR-EFW calculations was 2.4% using the semi-automated method and 2.2% for the PACS method. Measurements did not differ between the 8 sequences using the assisted method (p = 0.313) or the PACS (p = 0.118), while the time of planimetric measurement decreased significantly with a larger gap (p < 0.001) and in the assisted method compared to the PACS method (p < 0.01). Conclusion: Our simplified MR-EFW measurement showed a dramatic decrease in time of planimetric measurement without a decrease in the accuracy of weight estimates.

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

Abstract 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.

Comparison of conventional 2D ultrasound to magnetic resonance imaging for prenatal estimation of birthweight in twin pregnancy

BACKGROUND: During prenatal follow‐up of twin pregnancies, accurate identification of birthweight and birthweight discordance is important to identify the high‐risk group and plan perinatal care. Unfortunately, prenatal evaluation of birthweight discordance by 2‐dimensional ultrasound has been far from optimal. OBJECTIVE: The objective of the study was to prospectively compare estimates of fetal weight based on 2‐dimensional ultrasound (ultrasound–estimated fetal weight) and magnetic resonance imaging (magnetic resonance–estimated fetal weight) with actual birthweight in women carrying twin pregnancies. STUDY DESIGN: Written informed consent was obtained for this ethics committee–approved study. Between September 2011 and December 2015 and within 48 hours before delivery, ultrasound–estimated fetal weight and magnetic resonance–estimated fetal weight were conducted in 66 fetuses deriving from twin pregnancies at 34.3–39.0 weeks; gestation. Magnetic resonance–estimated fetal weight derived from manual measurement of fetal body volume. Comparison of magnetic resonance–estimated fetal weight and ultrasound–estimated fetal weight measurements vs birthweight was performed by calculating parameters as described by Bland and Altman. Receiver‐operating characteristic curves were constructed for the prediction of small‐for‐gestational‐age neonates using magnetic resonance–estimated fetal weight and ultrasound–estimated fetal weight. For twins 1 and 2 separately, the relative error or percentage error was calculated as follows: (birthweight – ultrasound–estimated fetal weight (or magnetic resonance–estimated fetal weight)/birthweight) × 100 (percentage). Furthermore, ultrasound–estimated fetal weight, magnetic resonance–estimated fetal weight, and birthweight discordance were calculated as 100 × (larger estimated fetal weight–smaller estimated fetal weight)/larger estimated fetal weight. The ultrasound–estimated fetal weight discordance and the birthweight discordance were correlated using linear regression analysis and Pearsons correlation coefficient. The same was done between the magnetic resonance–estimated fetal weight and birthweight discordance. To compare data, the χ2, McNemar test, Student t test, and Wilcoxon signed rank test were used as appropriate. We used the Fisher r‐to‐z transformation to compare correlation coefficients. RESULTS: The bias and the 95% limits of agreement of ultrasound–estimated fetal weight are 2.99 (–19.17% to 25.15%) and magnetic resonance–estimated fetal weight 0.63 (–9.41% to 10.67%). Limits of agreement were better between magnetic resonance–estimated fetal weight and actual birthweight as compared with the ultrasound–estimated fetal weight. Of the 66 newborns, 27 (40.9%) were of weight of the 10th centile or less and 21 (31.8%) of the fifth centile or less. The area under the receiver‐operating characteristic curve for prediction of birthweight the 10th centile or less by prenatal ultrasound was 0.895 (P < .001; SE, 0.049), and by magnetic resonance imaging it was 0.946 (P < .001; SE, 0.024). Pairwise comparison of receiver‐operating characteristic curves showed a significant difference between the areas under the receiver‐operating characteristic curves (difference, 0.087, P = .049; SE, 0.044). The relative error for ultrasound–estimated fetal weight was 6.8% and by magnetic resonance–estimated fetal weight, 3.2% (P < .001). When using ultrasound–estimated fetal weight, 37.9% of fetuses (25 of 66) were estimated outside the range of ±10% of the actual birthweight, whereas this dropped to 6.1% (4 of 66) with magnetic resonance–estimated fetal weight (P < .001). The ultrasound–estimated fetal weight discordance and the birthweight discordance correlated significantly following the linear equation: ultrasound–estimated fetal weight discordance = 0.03 + 0.91 × birthweight (r = 0.75; P < .001); however, the correlation was better with magnetic resonance imaging: magnetic resonance–estimated fetal weight discordance = 0.02 + 0.81 × birthweight (r = 0.87; P < .001). CONCLUSION: In twin pregnancies, magnetic resonance–estimated fetal weight performed immediately prior to delivery is more accurate and predicts small‐for‐gestational‐age neonates significantly better than ultrasound–estimated fetal weight. Prediction of birthweight discordance is better with magnetic resonance imaging as compared with ultrasound.

A Longitudinal Study on Fetal Weight Estimation at Third Trimester of Pregnancy: Comparison of Magnetic Resonance Imaging and 2-D Ultrasound Predictions

Objective: To prospectively compare magnetic resonance (MR) estimation of fetal weight (MR-EFW) performed at third trimester with ultrasound (US) estimation of fetal weight (US-EFW) and actual birth weight, and to evaluate factors influencing fetal growth rate near term. Methods: US-EFW and MR-EFW were calculated at a median of 33.0 and 37.7 weeks of gestation in 37 fetuses and plotted on curve centiles to predict birth weights at 39.3 weeks of gestation. The median absolute relative errors for predicted US-EFW and MR-EFW were calculated. Regression analysis was used to investigate the effect of different variables on fetal growth rate at 35.2 weeks of gestation. Results: The relative error of actual birth weight as predicted by US at 33.0 weeks was significantly higher compared with MR (7.33 vs. 4.11%; p = 0.001). This was also the case for fetal weight predicted by US at 37.7 weeks as compared with MR (6.63 vs. 2.60%; p < 0.01). Fetal growth rate was significantly and independently positively associated with the mothers weight and with gestational age at estimation (p < 0.05 for both variables). Conclusion: Fetal weight estimates predicted using MR at third trimester are better than those given by prenatal US. Fetal growth rate depends on fetal and maternal characteristics.

Repeatability of estimated fetal weight: Comparison between MR imaging versus 2D ultrasound in at- and near-term patients

INTRODUCTION Our aim was to evaluate the intra- and inter-observer variability and the impact of operator experience on the estimation of fetal weight (EFW) as measured by 2-dimensional ultrasound (2D-US) and magnetic resonance (MR) imaging. MATERIAL AND METHODS We estimated fetal weight in 46 singleton pregnancies at 35.6-41.4 weeks gestation using 2D-US according to the Hadlock formula and using MR imaging according to the equation developed by Baker. Each examination was performed twice, once by an inexperienced operator and once by an experienced operator. The MR-EFW was derived from the planimetric measurement of fetal body volume (FBV) using an assisted semi-automated method. Intra- and inter-observer variability was evaluated by Bland-Altman analysis. Regression analysis was used to investigate the effect of maternal BMI, delivery weight, diabetes and fetal gender on the differences in US-EFW between the inexperienced and experienced operators. RESULTS US-EFW showed higher intra-observer variability than MR-EFW, irrespective of operator experience. The 95% limits of agreement of MR were narrower compared with those of the US measurements. Similarly, US-EFW showed higher inter-observer variability than MR-EFW. MR-EFW improvement over 2D-US for the limits of agreement was 77.9% for intra-observer variability and 74.5% for inter-observer variability. Regression analysis showed that the differences between US-EFW measurements were not related to any of the tested variables. CONCLUSIONS Operator experience has a marginal impact on the variability of US-EFW and no impact on MR-EFW variability. The variability in US-EFW measurements is unpredictable.

Prenatal prediction of postnatal large-for-date neonates using a simplified method at MR imaging: comparison with conventional 2D ultrasound estimates

To evaluate the performance of a simple semi‐automated method for estimation of fetal weight (EFW) using magnetic resonance imaging (MRI) as compared with two‐dimensional (2D) ultrasound (US) for the prediction of large‐for‐dates neonates.

Prenatal prediction of small-for-gestational age neonates using MR imaging: comparison with conventional 2D ultrasound

Abstract Purpose: The purpose of this study is to evaluate the performance of estimating fetal weight (EFW) using magnetic resonance (MR) imaging as compared with two-dimensional (2D) ultrasound (US) in the prediction of small-for-gestational age neonates (SGA). Materials and methods: Written informed consent was obtained for this Ethical Committee approved study. Between March 2011 and May 2016, women with singleton pregnancies underwent US-EFW and MR-EFW within 48 h before delivery. US-EFW was based on Hadlock et al. and MR-EFW on the formula described by Backer et al. after planimetric measurement of the fetal body volume (FBV). Our outcome measure was performance in prediction of small-for-gestational age neonates by MR imaging versus US-EFW, using receiver-operating characteristic (ROC) curves. Results: Two hundred and seventy women were included in the study with 18 newborns (6.7%) of birthweight ≤10th, 12 (4.5%) ≤ 5th and 7 (2.6%) ≤ 3rd centile. The area under the ROC curve for prediction of birthweight ≤10th centile by prenatal MR imaging was significantly better than by US (difference between the AUROC = 0.060, p = .01; standard error = 0.023). Similarly, the area under the ROC curve for prediction of birthweight ≤5th centile by prenatal MR imaging was significantly better than by US (difference between the AUROC = 0.019, p = .03; standard error = 0.009). Finally, there was no significant difference between the areas under the ROC curve for the prediction of birthweight ≤3rd centile between the two imaging modalities (difference between the AUROC = 0.021, p = .13; standard error = 0.014). Conclusion: MR-EFW performed immediately prior to delivery predicts SGA neonates significantly better than US-EFW.

Prenatal prediction of postnatal large‐for‐dates neonates using a simplified MRI method: comparison with conventional 2D ultrasound estimates

To evaluate the performance of a simple semi‐automated method for estimation of fetal weight (EFW) using magnetic resonance imaging (MRI) as compared with two‐dimensional (2D) ultrasound (US) for the prediction of large‐for‐dates neonates.

Prenatal prediction of postnatal large-for-dates neonates using a simplified MRI method: comparison with conventional 2D ultrasound estimates: MRI vs 2D-US in prediction of neonatal macrosomia

To evaluate the performance of a simple semi‐automated method for estimation of fetal weight (EFW) using magnetic resonance imaging (MRI) as compared with two‐dimensional (2D) ultrasound (US) for the prediction of large‐for‐dates neonates.