The Transverse versus the Sagittal Approach in First-Trimester Uterine Artery Doppler Measurement

OBJECTIVE: The uterine artery pulsatility index (UtA-PI) is an important marker for predicting and assessing the risk of various complications such as pre-eclampsia and fetal growth restriction. The measurement of UtA-PI in the first trimester is usually conducted via the sagittal approach. The aim of this study was to evaluate UtA Doppler measurement using the transverse approach in the first trimester. METHODS: This was a prospective observational study of 50 women with singleton pregnancy at between 11-13+6 weeks of gestation. Uterine artery (UtA) Doppler variables were measured using both the transverse and sagittal approach. The two approaches were compared in terms of time required to complete the measurements and early diastolic notch. The sample t-test and Wilcoxon rank sign test were used to analyze the outcomes when appropriate. Bland–Altman plots were used to determine the agreement between the two approaches. A P-value <0.05 was considered statistically significant. Intra-class correlation (ICC) was used to evaluate the reliability of measurements. RESULTS: There were a total of 50 pregnant women who participated in the study and completed the study protocol. The mean age of all subjects was 29.6 years, and 24 (48%) were nulliparous. We observed no difference in terms of mean UtA-PI between the two approaches (sagittal: 2.04, transverse: 2.03; mean difference 0.01, CI −0.01, 0.04; p>0.309), nor in the means of any other UtA variables. However, there were differences between the two approaches in terms of early diastolic notch (sagittal: 11, transverse: 13; p>0.999) and the mean time required to complete the measurements (transverse: 21.7 s, sagittal: 24.3 s; p=0.001). The intra-class correlation coefficients (ICCs) were 0.985, 0.963, and 0.988 for the right, left, and mean UtA-PIs respectively. CONCLUSION: The transverse approach at a bladder depth of less than 5 cm performed better than the sagittal approach in the measurement of first-trimester uterine arteries. It may, thus, may be useful as a complementary approach in cases in which there is difficulty obtaining measurements using the sagittal approach.