Introduction
Monochorionic diamniotic twins are high risk pregnancies that can be
complicated (9-15% of all cases) by twin-to-twin transfusion syndrome
(TTTS) 1-3. This severe condition can lead to
polyhydramnios in the recipient twin, premature delivery and poor
perinatal outcome 4, 5. Currently, TTTS remains a
challenge in modern fetal medicine and in the absence of treatment
perinatal mortality is extremely high (>80%)6, 7.
Management of TTTS has evolved considerably over the last decades1-7. Presently, the fetoscopic laser ablation (FLA) of
the superficial placental anastomoses is the most common treatment
strategy. Many studies compared between amnioreduction (AR) of excess
amniotic fluid with FLA strategies and most concluded that FLA is the
optimal TTTS treatment, since it resulted in higher survival rate and
less neurological complications at six months of age8-11. However, the FLA procedure is limited to weeks
16-26 of gestation 12 and is heavily hindered by
anatomical restrictions such as anterior placenta. Moreover, the
incidence of neurodevelopmental impairment in TTTS survivors treated
with FLA is still high 8. Thus, no single treatment
seems to be associated with a clearly improved survival13.
The amniotic fluid volume increases
progressively throughout a normal singleton pregnancy; from 200 to 300
mL in week 16 to 1400 mL in week 40 14, 15, while
maintaining a linear relationship between amniotic pressure and
gestational age 16-18. A similar tendency exists in
normal twin pregnancy. However, it has been noted that amniotic pressure
in most cases of polyhydramnios and TTTS is higher than in case of an
uncomplicated gestations and it significantly falls with the amniotic
fluid drainage 19-23. A comprehensive literature
search did not reveal a consensus regarding the volume and rate of
amniotic fluid removal, as well as the intrauterine pressure during the
procedure. As a result there is neither a commonly accepted treatment
protocol, nor indicators for interruption of amniotic fluid drainage.
The clinical threshold to terminate the procedure is subjective and
based on the clinical experience.
In the present study we implemented a controlled AR procedure and
measured the relationship between amniotic pressure, volume removed and
blood flow of each twin during the procedure. We also analyzed the
long-term neurodevelopmental outcome of children born following a
pregnancy complicated by TTTS whose mothers underwent the controlled AR.