usually recognized as TTTS in the first impression.
About 25% of cases transferred to the Florida Institute
for Fetal Diagnosis and Therapy with a suspected
diagnosis of TTTS later turned out not to
fulfill the TTTS criteria. Those cases varied from simple
amniotic fluid volume discordance to isolated
polyhydramnios and isolated oligohydramnios [6].
Since September 2005, there were about 16 cases
transferred to Chang Gung Memorial Hospital,
Linkou Medical Center under the impression of
TTTS, four of the 16 cases were MC twins with selective
IUGR, one of the four cases eventually met the
criteria for TTTS after 2 weeks.
The main pathophysiologic basis of MC twins
with selective IUGR is the territory factor; it arises
from unequal sharing of the placenta in MC twins.
It differs from the vascular communicating factor
in TTTS.
The diagnosis of MC twins with selective IUGR
in ultrasound is:
1. MC placenta;
2. IUGR of the small twin, estimated fetal weight
below the 10th percentile in one twin of MC
pregnancy;
3. Lack of polyhydramnios/oligohydramnios sequel.
They can present as oligohydramnios in the small
twin but lack polyhydramnios in the appropriate for
gestational age (AGA) twin, or polyhydramnios in
the AGA twin but lack oligohydramnios in the
small twin.
Selective IUGR occurs in about 12% of twin pregnancies
[28]. The incidence of this process is similar
in dichorionic (DC) and MC twin pregnancies, but
the risk of neurologic damage may be greater in MC
twins [29]. Spontaneous demise of the twin with
selective IUGR may result in the concomitant demise
of the twin who is AGA in up to 40% of cases or in
neurologic damage of the AGA twin in up to 30% of
cases [27]. However, even in the absence of single
intrauterine fetal death, the risk of neurologic damage
may be increased in MC as compared with DC
twin pregnancies [29].
Current treatment of selective IUGR in MC
twins involves expectant management and early
delivery (if warranted), termination of pregnancy,