o_1977r8vv9vk1ts2ms0kd8pksa.pdf

322 E.P. Gaziano, U. F. Harkness
Gaziano et al. [76] described 11 pregnancies with
TTS from 101 multiple-gestation pregnancies using
high-resolution real-time ultrasonography and a comprehensive
assessment of the fetus that included detailed
biometry and a fetal anatomic survey with amniotic
fluid and placental assessment. Donor twins
tended to be severely growth restricted, with 7 of the
11 showing elevated S/D ratios. Amniotic fluid tended
to be decreased in the donor's sac and normal or increased
in the recipient's sac. Normal S/D ratios were
seen most frequently in the recipient fetus, although
abnormal velocimetry was seen in two fetuses.
Other authors studying suspected TTS patients
noted normal blood flow measurements in the umbilical
artery of some fetuses [77]. They confirmed the
observations that pathologic velocimetry patterns
usually affect the smaller (donor) fetus.
In another study, four pairs of twins with TTS
were described [78]. The three recipients for whom
blood flow in the middle cerebral artery (MCA) could
be measured had a decreased PI and each of the four
recipients had abnormal umbilical artery waveforms
(increased PI or absent end-diastolic flow). The middle
cerebral and umbilical artery PIs were normal in
the donors.
The heterogeneity of placental and clinical findings
for, and the lack of strict criteria for, the diagnosis of
TTS may explain some of the variability of findings
reported for Doppler in TTS.
Fig. 20.6. Zero diastolic flow and abnormal venous waveform
in the recipient fetus with TTS
Venous Waveforms
Umbilical venous blood flow sampling in twin pregnancies
using fetal Doppler ultrasonography was described
by Gerson et al. [26]. The sampling was normal
in cases of discordant growth due to abnormal
placentation but was abnormal in one fetus with TTS.
Pretorius et al. [75] described a biphasic venous
waveform in the umbilical vein at 29 weeks' gestation
in a fetus with TTS who also had Doppler echocardiographic
findings suggestive of tricuspid insufficiency.
Abnormal umbilical venous flow has been
seen in other cases of fetal hydrops and most likely
reflects right-sided cardiac failure. Figures 20.6 and
20.7 illustrate a case of fetal hydrops in TTS with an
abnormal venous waveform pattern and fetal abdominal
ascites.
Findings of reversed flow in the inferior vena cava
and reversed flow in the ductus venosus is suggestive
of right heart failure in a larger recipient twin [78].
In addition, echocardiography may demonstrate mitral
and tricuspid regurgitation in twins with ultrasound
evidence of hydrops [78].
Doppler velocimetry may differentiate between
twin pregnancies complicated by FGR and TTS. This
distinction is important since the death of one fetus
Fig. 20.7. Ascites in recipient twin from TTS
in TTS can be deleterious to the other, whereas death
of an FGR fetus in a diamniotic dichorionic twin gestation
poses less risk to the co-twin. Abnormal uterine
artery Doppler values and brain sparing can be
seen with both FGR and TTS [79]. Venous flow of the
larger twin in TTS can be abnormal [79]. If FGR is
due to poor placental function or chromosomal abnormality,
venous flow in the larger twin is expected
to be normal [79].
Outcome in TTS Pregnancies
Absent or reversed flow in five of the eight fetuses
with TTS was associated with perinatal death in each
instance [75]. Doppler abnormality in the setting of
TTS portends a poor outcome [75]. Gaziano et al.
[76] also noted increased morbidity and mortality in
TTS fetuses with abnormal velocimetry. The PI difference
in twins was greater in those destined to develop
fetal hydrops [31]. In another study of 23 sets of
twins with TTS, the following factors independently
predicted poor survival: absent or reversed end-dia-