Front Matter

The Conundrum of ASD Discordance in Maternal Twins 147

pairs is twin‐to‐twin transfusion syndrome (TTTS), also known as feto‐fetal
transfusion syndrome (FFTS). This is a complication of highly disproportion-
ate blood supply, resulting in high morbidity and mortality. It can affect mono-
chorionic twins or triplets where two or more fetuses share a chorion and
hence a single placenta. Chorion is the extraembryonic membrane that devel-
ops villi and becomes the fetal part of the placenta. TTTS is a very serious
complication affecting approximately 15% of maternal twin pregnancies. It
affects only monozygotic maternal twins sharing a single placenta and a single
chorion. As the placenta develops, the blood vessels form in such a way that
vessels from one umbilical cord connect up with vessels from the other. This
causes a sort of “short circuit” between the babies. As a result of their differing
blood supplies, each twin faces a set of challenges that require expert and expe-
rienced urgent care. The donor twin gets less blood than its sibling, causing it
to become anemic (lacking in red blood cells) and produce less urine, the main
ingredient of amniotic fluid. The fluid can continue to decrease (called oligo-
hydramnios) to the point of disappearing completely, causing the amniotic sac
to cling to the fetus. Because of this, the fetus may also appear to adhere to the

Superficial anastomosis

Recipient

Donor

Deep anastomosis

Figure 6.3 Twin‐to‐twin transfusion syndrome. In this disease of the placenta, which affects
maternal twins, the blood passes disproportionately from one baby to the other through
connecting blood vessels within their shared placenta. One baby, the recipient twin, gets
too much blood overloading his or her cardiovascular system, and may die from heart
failure. The other baby, the donor twin or “stuck twin,” does not get enough blood and may
die from severe anemia. If left untreated, mortality rates are nearly 100%. Source: http://
http://www.fetalhealthfoundation.org/fetal‐syndromes/twin‐to‐twin‐transfusion‐syndrome/.