FETAL
REDUCTION
Pregnancies
complicated by multiple gestation has been increasing as a result
of the wide spread use of fertility drugs. In such cases three
options exist. First the pregnancy can be electively aborted.
However when the pregnancy has been achieved after a great psychological
& economic cost, abortion is the least preferred option. The second
option is to proceed with pregnancy and delivery. The pregnant
woman faces almost certain preterm delivery, higher risks of pregnancy
induced hypertension, polyhydramnios etc. There is increased morbidity
and mortality to the fetus and increased morbidity to the mother.
Therefore fetal reduction is suggested as a therapeutic option
for continuation of pregnancies. It is also an option in the case
of multiple gestations wherein one fetus has an abnormality, the
other/s being normal. It is possible to selectively terminate
the affected fetus and continue gestation with the others.
Multifetal
reduction is a term applied to describe the technique of reduction
of fetus or fetuses in pregnancies with three or more fetuses.
Here all the fetuses are seen to be normal on ultrasound. The
final number of viable fetuses left behind is at least two or
sometimes one (depending on the patients desire).
Selective
reduction is a term applied to reduce one abnormal fetus in
a multiple pregnancy. This is most often done in the second trimester
and should only be done for dichorionic pregnancies, without fusion
of the placenta. Selective reduction should never be done for
monochorionic pregnancies as the other fetus may also die.
Fetal
reduction may be performed by the transvaginal or transabdominal
route. It is carried out in the first or second trimester of pregnancy.
It has been found that a good time to perform the procedure is
between the 11th & 12th week. Prior to this there is a chance
of natural resorption of a fetus/es in a multiple pregnancy. If
it is performed later in pregnancy it is probable that fetal resorption
will be incomplete. This may increase the chances of developing
maternal disseminated intravascular coagulation. The longer the
patient waits to undergo a selective reduction the greater is
the psychological stress to the patient.
At
BACC the most commonly performed method is an intrathoracic /
intracardiac injection of potassium chloride. A careful survey
of all the sacs and embryos is done by ultrasound prior to the
procedure. Selection of the embryos to be reduced is based on
this assessment in cases where all the fetuses look normal. The
sac/s closer to the fundus is chosen. It is preferable to choose
the embryos, which are smaller. The placentae of the sacs chosen
should be separate from each other. Fusion or vascular communications
between the placenta result in damage to the other fetus. Under
aseptic conditions a 22-gauge needle is inserted in the gestational
sac and guided (ultrasound) into the heart or thorax of the fetus.
Potassium chloride solution (2 mEq / ml) is injected in 2 ml increments
until cardiac inactivity is confirmed on ultrasound. Absence of
cardiac activity should be ascertained by a scan done 15 minutes
after the procedure. If the fetal heart is still present the procedure
needs to be repeated.
Various
other methods used for fetal reduction are air embolisation exsanguination
and cardiac tamponade using ice-cold ringer lactate solution,
into the pericardium or thorax. The risks associated with fetal
reduction are infections, septic abortion, aminonitis, bleeding
or damage to the remaining fetus. The risk of developing a coagulapathy
in selective termination is probably very small. Miscarriage rates
after multifetal reduction range from 10-20%. Operator experience
has a definite bearing on the outcome.
