P09.04: The influence of placental location according to the pulse repetition frequency used on first trimester three dimensional placental vascular indices

Abstract

To evaluate the influence of placental location on first trimester three dimensional placental vascular indices according to the value of the pulse repetition frequency (PRF) used. Seventeen pregnant women with singleton pregnancies were scanned at 12 weeks of gestation. In 10 cases the placenta was located anterior and in 7 posterior. VOLUSON 730 Expert (GE) with VOCAL software and histogram facility was used. Flow index (FI), vascular Index (VI) and vascular flow index (VFI) were calculated. Measurements were done at both 0.9 and 2.4 kHz. Student's t test was used for comparisons. In total, VI and VFI were higher when using 0.9 kHz PRF than with 2.4 kHz PRF (p = 0.001 and p = 0.0004 respectively). FI did not significantly varied (p = 0.41). Anterior placenta showed significantly higher 3-D vascular indices at 0.9 kHz PRF than at 2.4 kHz (p = 0.003, p = 0.009, p = 0.001 for VI, FI and VFI respectively). On the contrary, when the placenta was located posterior, none of the 3-D indices was significantly different at either 0.9 or 2.4 kHz PRF. FI at 0.9 kHz PRF was significantly higher when the placenta was located anterior than when it was posterior (p = 0.009) while the rest of the measurements did not significantly vary. Changes in 3-D vascular indices according to the values of the PRF used are more pronounced when placenta is located anterior than when it is posterior. The use of higher PRF values could be better for studies including women with both, anterior and posterior, placentas.