Umbilical artery Doppler velocimetry in normal pregnancies from 11(+0) to 13(+6) gestational weeks: a Taiwanese study.

OBJECTIVE: The aim of this study is to investigate the relationship between umbilical artery flow and gestational age (GA) at 11-13(+6) weeks in normal pregnancy in the Taiwanese population. MATERIALS AND METHODS: Two hundred and fifty-three normal singleton pregnancies with GA ranging from 11 to 13(+6) weeks were included in this study. The velocity of systolic, diastolic, and pulsatility index (PI) of the umbilical artery, and the mean velocity of the umbilical vein were recorded. RESULTS: One hundred and eighty-seven participants fulfilling the inclusion and exclusion criteria were analyzed. The mean maternal age was 31 (range 19-45) years, with a corresponding GA of 12(+4) (range 11-13(+6)) weeks. The absence of end-diastolic velocity of the umbilical artery was observed in most of our cases (90.1%). No significant change was found in the vascular indices with GA for the mean velocity of the umbilical vein (mean velocity = 0.923 × GA - 1.594, r = 0.1497, p = 0.115). The systolic velocity of the umbilical artery and PI, however, behaved differently from the other variables. There was a significant increase in systolic velocity with GA [systolic wave (S wave) velocity = 0.237 × GA + 2.267; r = 0.149, p = 0.041]. By contrast, the PI showed a significant decrease in relation to the GA (PI = -0.016 × GA + 4.068; r = 0.196, p = 0.007). CONCLUSION: The S-wave velocity of the umbilical artery increased with GA. By contrast, the PI of the umbilical artery showed a decreasing trend with GA. This may ensure optimal placental perfusion, which is necessary to accommodate the increased blood flow to the developing fetus. Furthermore, an absence of end-diastolic velocity in the first trimester and early second trimester was usually seen.