Background
Fetal environment has become a subject for increasing interest when studying health and disease in adults.
Monozygous (MZ) twins, especially gestations complicated with twin
-
twin transfusion syndrome (TTTS), offer
a unique opportunity to study adverse
developmental programming of the cardiovascular system. TTTS affects
about 10% of pregnancies with a common placenta
because of
unbalanced blood flow across deep arteriovenous
connecting vessels
.
The d
ivergent hemodynamic load
s
of the donor and the recipie
nt fetus
often result in
myocardial hypertrophy of the recipient heart.
The aims of this thesis were to evaluate intrauterine environmental contributions to vascular functions in twins
with discordant birth weight (Paper I), to study long term effects of
TTTS on cardiac structure and function
(Paper II and IV) and to determine infant survival and neonatal outcome after fetoscopic laser coagulation
therapy of TTTS in Sweden (Paper III).
Methods and Results
An observational study of 31 twin
-
pairs, mean age
8 years, with discordant weight at birth, showed that systolic
blood pressure (SBP) was higher and endothelial function
lower
in the
at birth
smaller twin. In MZ twins with a
history of TTTS (n= 9 pairs), there was no significant difference in SBP, but do
nor twins had narrower carotid
arteries than recipient twins and carotid strain was higher (Paper I).
Echocardiography of 11 TTTS twin
-
pairs, mean age 9.6 years, prenatally treated with amnioreductions, showed
no difference in cardiac structure but recip
ients had significantly lower diastolic ventricular filling
compared
with
donors
(Paper II). When examining a laser treated cohort of 19 TTTS twin
-
pairs, mean age 4.5 years, and
19 age
-
matched singleton controls,
we
found
signs of a minor decrease in early
diast
olic ventricular filling in
recipients compared
with
donors,
but
no
difference
s
in heart function or structure compared
with
controls (Paper
IV).
From a hospital
-
based register of the first Swedish cohort of laser treated TTTS pregnancies (n = 71),
we found
that overall survival from treatment to one
-
year of age was 46%, and that in 61% of gestations, at least one twin
survived infancy. Mean gestational age at birth was 30 weeks and mechanical ventilation was needed in 46% of
live
born twins (Paper
III).
Conclusions
Exposure to fetal growth retardation may contribute to higher
blood pressure
, arterial narrowing and endothelial
dysfunction in childhood (Paper I). Fetal and infant survival after fetoscopic laser coagulation of TTTS is
still
l
imited
. I
f very preterm delivery is necessary, the neonatal team has to prepare for taking care of two high risk
neonates mostly requiring respiratory support (Paper III). Despite different and severe fetal cardiac loading
conditions, our long
-
term
follow
-
up
studie
s of twins surviving TTTS showed an overall cardiac structure and
function within normal range. The signs of reduced diastolic function found in the group treated with
amnioreductions (Paper II) were less pronounced in the laser treated cohort (Paper IV).
These observations indicate that the cardiac morbidity caused by TTTS resolves in childhood. This has
important implications as clinical decision making in TTTS frequently involves choosing between accepting
increased fetal cardiac morbidity in the recipi
ent twin and
delivery of two very preterm babies
