Longitudinal Blood Flow in Shared (Arteriovenous Anastomoses) and Non-Shared Cotyledons in Monochorionic Placentae

Wee, L.Y.; Sullivan, M.; Humphries, K.; Fisk, N.M.

doi:10.1016/j.placenta.2006.09.001

« Previous Next »Placenta
Volume 28, Issue 5 , Pages 516-522, May 2007

Longitudinal Blood Flow in Shared (Arteriovenous Anastomoses) and Non-Shared Cotyledons in Monochorionic Placentae

L.Y. Wee
- Experimental Fetal Medicine Group, Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Campus, London, UK
- Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, London, UK
- Corresponding author. Fetal Medicine Unit, Elizabeth Garrett Anderson Hospital, Huntley Street, London WC1E 6DH, UK. Tel.: +44 20 7380 9872.
M. Sullivan
- Experimental Fetal Medicine Group, Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Campus, London, UK
K. Humphries
- Radiological Science Unit, Hammersmith Hospital, Du Cane Road, London, UK
N.M. Fisk
- Experimental Fetal Medicine Group, Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Campus, London, UK
- Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, London, UK

Accepted 3 September 2006. published online 03 November 2006.

Abstract

Objectives

In this study we aimed to quantitate monochorionic twin placental blood flow in vivo through arterio-venous anastomoses (AVA) and corresponding vessels within normal cotyledons.

Methods

The topography of chorionic plate vasculature was mapped using colour Doppler in ten monochorionic diamniotic twin (MCDA) pregnancies. Cotyledonary flow was derived by insonation of chorionic veins draining normal (n=10) and paired control shared cotyledons (n=10). Venous volume flow was calculated from five determinations of vessel diameter and three of time average mean velocity (TAMV). Measurements were repeated every 2–4weeks from 18 until 32weeks’ gestation.

Results

Blood flow through non-shared and shared cotyledons increased with gestation (p<0.0001). Median flow at 28weeks through shared cotyledons was 16ml/min (15–21) (median, interquartile range), lower than in shared cotyledons (31, 25–35) (p<0.001), as was median volume flow across gestation calculated as area under the curve (shared cotyledons 126 (122–167), control cotyledons 269 (214–274), p=0.01). However, velocity was similar, with the difference due to smaller vein diameters draining shared compared to normal cotyledons (mean 3.6mm (SD 0.8) vs. 4.5mm (0.8), p=0.004). Ex vivo quantitation of insonated cotyledons and of all cotyledons confirmed the difference in vein diameter in the placentae studied.

Conclusions

Blood flow through shared cotyledons was lower across gestation than through paired normal cotyledons in the placenta studied due to the smaller diameter of the AVA vessels. The size of AVAs rather than simply their presence and direction may contribute to determining transfusional imbalance in monochorionic twins.

Keywords: Doppler velocimetry, Ultrasound, Arterio-venous anastomosis, Shared cotyledon, Normal cotyledon, Non-shared cotyledon, Monochorionic placenta, Vascular anastomosis, Flow rate, Monochorionic twins