Impact of bladder filling on uterine artery Doppler variables in the first trimester of pregnancy

OBJECTIVE: Uterine artery (UtA) Doppler examination is used in the first trimester to assess the risk of developing preeclampsia, with a standardized technique. However, the impact of bladder filling on UtA circulatory impedance in pregnancy has not been previously studied. This study aimed to examine the effect of bladder distension on UtA-pulsatility index (PI) and peak systolic velocity (PSV) in the first trimester of pregnancy. METHODS: The authors conducted a prospective repeated-measure study on pregnant women presenting for first-trimester screening for preeclampsia. Right and left UtA Doppler velocimetry was first measured with a full bladder. Bladder volume was recorded. After the patients had voided their bladder, a repeat Doppler measurement was performed. The UtA PI and PSV were recorded on each side. The Wilcoxon signed-rank test was used to compare UtA variables before and after bladder voiding. RESULTS: The authors enrolled 45 patients. Mean gestational age at exam was 12.1 weeks. When women were studied with full bladder, median UtA-PI was 1.73 (inter-quartile range, [IQR] 1.49, 2.28) on the right and 1.71 (1.46, 2.11) on the left side. After bladder voiding, values were 1.83 (IQR 1.58, 2.20) and 1.78 (1.40, 2.18). The difference was not statistically significant (P = .26 and 0.80). Similarly, no difference was found in UtA-PSV before and after bladder voiding on either side (P = .22 and .70). CONCLUSION: In the first-trimester of pregnancy, bladder distension does not significantly modify uterine artery Doppler variables.