Congenital Malformations in Twins
The incidence of malformations in twins varies by
chorionicity. The overall risk of congenital malformation
in twins is 600/10,000 twin births. Monozygotic
twinning is associated with midline defects such as
holoprosencephaly, neural tube defects, and cloaca
extrophy [3]. Overall, MC twins have a two- to
three-fold higher rate than DC twins [3]. In a congenital
anomaly that is lethal, fetocide is unnecessary
except unless polyhydramnios or TTTS occurs, and
expectant management is the sensible option.
For example, in anencephaly, if fetocide is considered,
bipolar cord occlusion is the choice because
potassium chloride injection is not feasible due to
the communicating vessels that almost always
exist between the two twins. The bipolar could be
inserted into the uterus via a 2.5–3.5 mm trocar.
Cord insertion near the fetus is better than near
the placenta to be coagulated to prevent thrombosis
or thermo damage to another twin.