P12.13: Reproducibility and clinical relevance of antenatal detection of arterio-arterial anastomoses by Doppler placental assessment in monochorionic twin pregnancies

Objectives: To evaluate the reproducibility of Doppler antenatal
detection of arterio-arterial anastomoses (AAA) in monochorionic
twin pregnancies in a centre other than where this method was first
systematically applied and to correlate the prenatal identification of
AAA with the clinical outcome of these pregnancies.
Methods: 21 monochorionic diamniotic twin pregnancies and
one dichorionic triamniotic triplet seen at the Twin Clinic at
the University of Brescia were recruited prospectively (October
2002–February 2003). After routine ultrasonographic assessment,
AAA were searched using Color or Power and spectral Doppler. The
presence of AAA was confirmed postnatally by placental injection
studies. Data on the presence of AAA obtained from injection studies
were compared with Doppler findings to establish sensitivities and
specificities of prenatal Doppler investigation. Clinical outcome
of the two groups (with or without AAA detected in utero)
were compared.
Results: Data of 19 patients were available for the analysis. AAA
were detected in 12 cases (63%) antenatally and in 16 (84.2%) at
injection study. Sensitivity and specificity of Doppler for detecting
AAA were 75% and 100% respectively. Detection rates increased
at advanced gestations and with anterior/fundal placentae. The
incidence of twin–twin transfusion syndrome (TTTS) was higher in
the group with no AAA detected in vivo compared to the group with
AAA found with Doppler (28.6% vs 16.6%), but not statistically
significant (P = 0.5). All TTTS cases with an AAA found in utero,
regressed spontaneously or after one amnioreduction. All cases with
a birthweight discordance > 20% and no signs of TTTS, had an
AAA detected with Doppler and showed intermittent absent/reverse
diastolic flow in the umbilical artery of the smaller twin.
Conclusion: This study confirmed the reproducibility and clinical
relevance of AAA Doppler detection in vivo in monochorionic
pregnancies.