Twin Placental Mapping Study

Thanks to support from the Wiseman trust, since October 2018 we have been running the TWIN PLACENTAL MAPPING STUDY at Imperial College NHS Healthcare Trust.  This is a study of identical twins who share a placental – monochrionic diamniotic (MCDA) twins.

As a research group, we want to understand if it is possible to use existing ultrasound technology to look at the blood vessels within the placental of MCDA twins to understand better how and where they join.  We think it is important to do this because how and where these blood vessels join within the MCDA placenta predicts the risk of developing serious complications such as twin-twin transfusion syndrome (TTTS), selective growth restriction (sIUGR) or twin anaemia-polycythemia syndrome (TAPS).  By having this knowledge earlier in pregnancy we hope to be able to monitor better and intervene sooner to make things better for the twins and their families.

This study will also contribute to a larger planned clinical trial of using High Intensity Focused Ultrasound (HIFU) as a non-invasive method of occluding placental vasculature in Twin-Twin Transfusion Syndrome.  We are planning to start a first-in-human clinical trial in 2020, and completing the twin placental mapping study is vital to being able to run the clinical trial.

We are currently offering an extra scan for research to all women who attend Imperial NHS Healthcare Trust for pregnancy care between 12-26 weeks of pregnancy if they are pregnant MCDA twins.  In this scan we check over the twins and also find where and how the blood vessels within the placenta join.  We are currently working on defining a method of predicting whether TTTS, TAPS or sIUGR will occur and although early, we are starting to present our results to the scientific community (see below).  We are preparing journal article describing the methods we use to find the region where the circulation of the twins join, and how the position of this area within the placental affects the growth of the twins.

We also have a particular interest in the best way to deliver patient education about the challenges of MCDA twin pregnancy, as we believe that my making knowledge accessible we empower patients to have the best pregnancy possible for their individual circumstances.  We have developed the ways we give this information with the assistance of focus groups made up of parents who have had complicated and difficult MCDA pregnancies, and are still developing more resources based on this feedback.  We too, are in the process of learning.

So far, we have recruited 25 patients with MCDA twins, 15 of whom have already had their twins, and we welcome contact from anyone interested in participating in the study on twins@imperial.ac.uk.

 

The placenta of twins as it’s never been seen before…

 

Abstracts accepted:

Expert Pregnancy Imaging, London, May 2019

MAPPING OF THE PLACENTAL ANGIOARCHITECTURE IN MONOCHORIONIC TWIN PREGNANCIES USING DIFFERENT COLOUR DOPPLER FILTERS

Authors: Serena Girardelli, Caroline J Shaw, Christoph C Lees

Institution: Queen Charlotte’s and Chelsea Hospital, Imperial College NHS Trust, London

Background: Placental angioarchitecture is understood to be important in determining the prognosis for monochorionic diamniotic (MCDA) twin pregnancy, however it is rarely examined prenatally unless fetoscopy is indicated.  The degree of unequal sharing of the single placental mass contributes to the risk of selective intrauterine growth restriction (sIUGR).  Arterio-venous anastomoses are thought to be causative of twin-twin transfusion syndrome (TTTS) and arterio-arterial anastomoses to be protective against.  The presence of veno-venous anastomoses is reported to increase the risk of neurological damage in the surviving twin following co-twin death.  Methods of identifying the vascular equator and characterising placental anastomoses sonographically have been previously described, but remain underused, potentially denying important prognostic information to parents and clinicians alike.

Objectives: To determine the feasibility of using a systematic sonographic approach for mapping of the vascular equator and detection and characterization of placental anastomoses within the angioarchitecture of the MCDA placenta.

Methods: Twenty MCDA placentae (55% anterior and 45% posterior) were examined between 12-26 weeks’ gestation.  The patients’ mean BMI was 6.96 (ranging between 20.08 e 44.00). Different colour Doppler modalities were used to identify placental vessels between the two cord insertions: colour Doppler with typical obstetric settings (CD) (Fig. A), colour Doppler with reduced pulsatility repetition frequence (PRF) (Fig. B), advanced dynamic flow (ADF) (Fig. C) and superb microvasculature imaging (SMI) (Fig. D). Pulse wave Doppler was used to characterise the blood flow within the vessels identified.  Ultrasound imaging was recorded for offline analysis and placental “maps” were created. Although their characterization was more challenging, the vascular equator was identifiable in 16 out of 20 patients; in 14 of these, identification of those vessels crossing the equator and thus the creation of a “vascular map” was achieved.

Results: Twenty MCDA placentae (55% anterior and 45% posterior) were examined at mean gestational age 17+3 (12+2 – 25+5) – (patients’ BMI 26.96 (20.08 – 44.00)). Traditional colour Doppler identified umbilical cord insertions and few placental vessels; by reducing the PRF the interpretation of the angioarchitecture impossible due to sonographic “noise”. With ADF, however, combining a broadband frequency with a high frame rate allowed for a more definite angioarchitecture depiction and vessels to be characterised; with SMI, microscopic vessels were identifiable.  Although characterization of vessels was more challenging, this allowed identification of the vascular equator.

Conclusions: A “multi-filter” approach to angioarchitecture sonographic examination using different colour Doppler techniques is of fundamental assistance when characterising anastomoses and determining vascular equator in twin monochorionic placentas.

 

 

ISUOG, Berlin, October 2019

1) Short Oral Presentation: Multiple Pregnancy

Mapping of the placental angioarchitecture in monochorionic twin pregnancies using different colour Doppler filters

  1. Girardelli2, 3, C. Shaw2, 1, C. Lees2, 1 1. Imperial College Healthcare NHS Trust, London, United Kingdom; 2. Queen Charlotte’s and Chelsea Hospital, Imperial College London, London, United Kingdom; 3. Università Vita e Salute San Raffaele, Milan, Italy

Objectives To determine the feasibility of using a systematic sonographic approach for mapping of the vascular equator and detection and characterization of placental anastomoses within the angioarchitecture of the MCDA placenta. Methods Twenty MCDA placentae (55% anterior and 45% posterior) were examined between 12-26 weeks’ gestation. The patients’ mean BMI was 26.96 (ranging between 20.08 e 44.00). A Canon Aplio US machine was used to apply different colour Doppler modalities to identify the vascular equator and placental vessels between the two cord insertions (see image below). Pulse wave Doppler characterised the blood flow within the vessels identified. Ultrasound imaging was recorded for offline analysis and placental “maps” were created. Results Traditional colour Doppler identified umbilical cord insertions and few placental vessels; reducing the PRF caused sonographic “noise” that made mapping impossible. With ADF, however, combining a broadband frequency with a high frame rate allowed for a more definite angioarchitecture depiction; with SMI, microscopic vessels were identifiable. Although their characterization was more challenging, the vascular equator was identifiable in 16 out of 20 patients; in 14 of these, vessels crossing the equator were identified and thus the creation of a “vascular map” was achieved. Conclusions A “multi-filter” approach to angioarchitecture sonographic examination using different colour Doppler techniques is of fundamental assistance when characterising anastomoses and determining vascular equator in twin monochorionic placentas.

 

2) Electronic Poster: Multiple Pregnancy

Antenatal prediction of increased twin–twin transfusion syndrome (TTTS) risk at 14 weeks using different Colour Doppler filters

  1. Girardelli2, 1, C. Shaw2, 3, C. Lees2, 3 1. Università Vita e Salute San Raffaele, Milan, Italy; 2. Queen Charlotte’s and Chelsea hospital, Imperial College London, London, United Kingdom; 3. Imperial College Healthcare NHS Trust, London, United Kingdom

Abstract Body A P2 22-year-old was diagnosed with a monochorionic diamniotic (MCDA) twin pregnancy at her routine first trimester scan. At 14 weeks an additional ultrasound examination of her placenta was performed as part of a research study into the feasibility of mapping of placental angioarchitecture in the monochorionic placenta with a Canon Aplio Ultrasound machine. Her placenta was examined using different colour Doppler filters (Figure 1). The vascular equator and placental blood vessels crossing this region were identified using colour Doppler and characterized using pulsed-wave Doppler.
The presence of large caliber arterio-venous anastomoses indicated an elevated risk of developing TTTS. The presence of deep veno-venous anastomosis (VVAs) suggested that in case of co-twin demise, the recipient would be at higher risk for neurological sequelae or in utero death secondary to acute hypotension. Following a normal 16 week ultrasound examination at 18 weeks the patient was found to have amniotic fluid discrepancy with selective intrauterine growth discrepancy of fetus B (20% weight discrepancy with fetus A) and normal arterial and venous Doppler for both twins. She was managed conservatively for one week after which intrauterine fetal death of both twins was confirmed.