Umbilical-placental blood flow gradient during the early second trimester of pregnancy

To characterize umbilical-placental blood flow gradient during early second trimester of pregnancy.

Forty normal pregnant women with a singleton fetus gave their informed consent to participate in this study. All scans were preformed between 12 and 20 weeks' gestation using the simultaneous multigate spectral Doppler imaging (MS-SDI) modality available on the Diasonics Synergy system. The umbilical-placental circulation was scanned at three locations: (1) umbilical artery at the cord insertion, (2) superficial placenta at a point close to the cord insertion, and (3) deep placenta branches at the area adhere to the decidua basalis. The mean value of pulsatility index (PI) and resistance index (RI) were recorded.

PI and RI were both significantly lower in the superficial and deep placenta compared with the cord insertion area. No significant differences were found comparing between superficial and deep placenta. In 30 women we found lower values and in 10 women we found a higher value of PI and RI in the superficial and deep placenta compared with the cord insertion. Four of five cases with complicated pregnancies occurred in patients with negative placental gradient compared with only one case with positive placental gradient (p < 0.05).

In this preliminary report the umbilical placental blood flow gradient was characterized during the early second trimester of normal pregnancy. The presence of decreasing gradient was established. Absent or opposite gradient between the umbilical artery and the placental vessels was associated with adverse pregnancy outcome.