Prenatal sonographic diagnosis of single umbilical artery: Emphasis on the absent side and its relation to associated anomalies.

OBJECTIVE: To determine the absent side of a single umbilical artery (SUA) and to evaluate whether associated anomalies are related to the side of the missing artery in a Taiwanese population. MATERIALS AND METHODS: We retrospectively studied SUA fetuses from our computer database of fetal ultrasound in a tertiary medical center in Southern Taiwan. All cases were diagnosed as SUA prenatally using conventional scanners of two- and three-dimensional (2D and 3D, respectively) ultrasound, as well as color, power, and high-definition Doppler. The absent side of UA and associated anomalies were analyzed. RESULTS: From September 2006 to November 2011, 31 fetuses with SUA were diagnosed prenatally by ultrasound and all were enrolled for this series. The incidence was estimated to be 1:556 (0.18% = 31/17,086). The mean maternal age was 29.2 years (range, 15-36 years) and the mean fetal age was 30.0 weeks of gestation (range 18-36 weeks). Notably, the left-absent UA was detected in 16/31 (52%) fetuses, compared with the right-absent UA in 15/31 (48%) cases. In addition, congenital anomalies were noted prenatally in 2/16 (13%) fetuses with left-absent UA and in 3/15 (20%) fetuses with right-absent UA. CONCLUSION: In SUA fetuses, the absence of UA appears to occur equally at each side. Moreover, this study showed no significant difference between either side of missing UA and associated anomalies after statistical examination.