Hemodynamic adaptation of the right ventricle in monochorionic twin pregnancies complicated by twin-to-twin transfusion syndrome or selective growth restriction

Congenital heart disease occurs more frequently in neonates who survived Twin
to Twin Tranfusion syndrome (TTTS) and selective intrauterine grwoth
restriction (sIUGR) than in neonates after uncomplicated pregnancies. Around 7
% of the recipients in monochorionic twin pregnancies complicated by TTTS will
develop right ventricle outflow tract obstruction (RVOTO). The incidence in
donors of TTTS or the biggest twin in sIUGR is still unknown. The pathogenesis
of RVOTO is not yet fully understood.

Neonatologists must be aware of this cardiovascular abnormality, because RVOTO
may be progressive and require immediate treatment or surgery after birth.
Understanding the pathogenesis and developmental patterns of RVOTO can aid an
early detection of RVOTO and could improve prenatal and neonatal care of this
complicated pregnancies in the future.

The primary objective of this study will be to evaluate the cardiac adaptation
due to hemodynamic changes in monochorionic twin pregnancies complicated by
TTTS and sIUGR, by evaluating the size and the growth pattern of the pulmonary
artery and the right ventricle function in the recipient twin. In this way we
can evaluate etiology and pathogenesis of RVOTO, as well as determine risk
factors for and/or prognostic factors in RVOTO.

Observational prospective cohort study.

Women pregnant with monochorionic twin pregnancies, both complicated as
uncomplicated, receive ultrasound examinations at least biweekly. In subjects
included in this study additional measurements focused on pulmonary artery size
and growth, right ventricle function and flow velocity waveforms of pulmonary
artery and veins of the recipient twin will be added to the measurements
according to local protocol. In complicated cases the frequency of the
examinations can be higher on clinical indication and depends on the specific
situation of the patient. Additional measurements will be done maximum once a
week.

No risks are known for prenatal ultrasonographic examination. A minimal burden
is prolonged ultrasonographic examination time. Next to the routine (at least
biweekly) ultrasound in these high-risk pregnancies which normally takes about
half an hour, some extra measurements will be done in about 5-10 minutes.

The potential benefit for participating is an early and accurate diagnosis of
RVOTO for the foetusses of the participating woman, leading to adequate post
partum care by neonatologists as well as adequate counseling pre-partum.