Recommendation ID

What is the most accurate prenatal screening marker for TAPS, including middle cerebral artery peak systolic velocity (MCA‑PSV)?

Any explanatory notes
(if applicable)

Why the committee made the recommendations
There was limited evidence for screening and diagnostic monitoring for twin anaemia polycythaemia sequence (TAPS). The committee discussed, based on their expertise, that there is also limited evidence on the natural history of spontaneous TAPS and effective interventions for it in uncomplicated monochorionic pregnancies. They agreed that its incidence is likely to be low, so they could not recommend screening for it in women whose monochorionic pregnancy is uncomplicated.

The committee agreed that monitoring would be beneficial for women with the complications in recommendations 1.4.37 and 1.4.38. They recommended screening for TAPS in this population for 2 reasons:

Complicated monochorionic pregnancies have an increased risk of fetal and neonatal death and morbidity. Diagnosing TAPS as a further complication is likely to influence how the woman's pregnancy is managed, including the timing of preterm birth.

Advanced TAPS (stages 3 and 4) is associated with abnormal fetal umbilical artery and ductus venosus doppler parameters, or signs of fetal cardiac failure in the anaemic baby. These can also occur in a number of other conditions, so the diagnosis of severe TAPS (either alone or as a comorbidity) may be missed if it is not specifically screened for.

The committee concluded that for women who have a pregnancy in which TAPS is a comorbid complication or is of advanced stage, the risk to the babies without diagnosis and intervention is likely to be greater than the potential harms of interventions. These include preterm birth or potential in‑utero therapies, such as in‑utero transfusion, in pre-viable or extremely premature pregnancies.

The committee agreed that when TAPS is suspected, women should be referred to a tertiary level fetal medicine centre. They felt that the benefits of managing complicated monochorionic pregnancies in this setting would outweigh the potential disadvantages of inconvenience of travel and transfer to units away from home. The committee decided not to specify diagnostic criteria because they wanted to emphasise the importance of referral to a tertiary level referral centre when TAPS is suspected, so that decisions about further assessment and management can be made with each individual woman.

Given the limited evidence on the diagnostic accuracy of middle cerebral artery peak systolic velocity (MCA‑PSV) for all types of monochorionic twins, regardless of complications, and uncertainties about the natural history of TAPS and its management, the committee decided to make a research recommendation to inform future guidance.

How the recommendations might affect practice
The recommendation may increase the number of assessments of women with complicated monochorionic pregnancies and referral for appropriate management. However, the committee agreed that any increase in referrals would be offset by the benefits of better detection and management of complicated monochorionic pregnancies.

Full details of the evidence and the committee's discussion are in evidence review C: screening for TAPS.

Source guidance details

Comes from guidance
Twin and triplet pregnancy
Date issued
September 2019

Other details

Is this a recommendation for the use of a technology only in the context of research? No  
Is it a recommendation that suggests collection of data or the establishment of a register?   No  
Last Reviewed 30/09/2019