Determining a method for description and evaluation of heterogeneity of perfusion in the third-trimester placenta.

OBJECTIVES

Many critical obstetric pathologies are associated with deficiencies in placental perfusion. However, there are limited diagnostic tools available to evaluate this and there is marked variability. We previously used the validated tool, Three-Dimensional Fractional Moving Blood Volume (3D-FMBV), combined with infra-red camera tracking technology to quantify perfusion in the entire third-trimester placenta. This pilot study aimed to describe and evaluate the heterogeneity of placental perfusion, visualise this as a 'perfusion map,' and assess changes over gestation.

METHODS

This single-centre, prospective, cross-sectional study included 27 uncomplicated, third-trimester singleton pregnancies with anterior placentas. Multiple 3D Power Doppler Ultrasound (3D-PD-US) volumes were acquired with infra-red camera tracking coordinates, stitched and manually segmented to calculate the entire placental 3D-FMBV and volume. Heterogeneity was described using the coefficient of variation (CoV) of 3D-FMBV between defined cubic regions.

RESULTS

In third-trimester placentas, mean CoV was 34.1 % (±5.0), declining as global perfusion increased (p = 0.02). With advancing gestation, perfusion non-significantly increased (p = 0.11) and became more homogenous (p = 0.27), while overall placental volume significantly increased (p = 0.02). Two-way mixed measure ICCs were 0.78, 0.63 and 0.95 for global 3D-FMBV, CoV and placental volume respectively.

CONCLUSION

This study successfully reconstructed entire third-trimester placentas using infra-red camera tracking technology, quantified perfusion using 3D-FMBV and demonstrated its heterogeneity. As gestation advances, perfusion appears to increase and become more uniform, potentially reflecting greater involvement of the placental bed to maximise fetoplacental exchange. Future work will explore automating our method, evaluating a larger cohort, and assessing differences in complicated pregnancies at-risk of stillbirth.