Anemia of Prematurity - Portal Neonatal

heart. Twin reversed arterial perfusion (TRAP) sequence occurs when an acardiac twin
receives all of the blood supply from the normal "pump" twin. This only occurs in
monochorionic twins. Blood enters the acardiac twin in a reversed perfusion manner. Blood
enters this fetus via an umbilical artery and exits via the umbilical vein. The excessive
demands on the normal "pump" twin can cause cardiac failure in that twin.
• Twin-to-twin transfusion syndrome: This syndrome occurs in monochorionic/monoamniotic or
monochorionic/diamniotic twins. Vascular anastomoses in the monochorionic placenta result
in transfusion of blood from one twin (ie, donor) to the other twin (ie, recipient). One
classification scheme separates TTTS into severe, moderate, and mild forms.
o Severe TTTS presents early in the second trimester (16-18 weeks' gestation). A
difference of more than 1.5 weeks' gestational size between twins occurs. Severe
TTTS has a 60-100% mortality rate. Polyhydramnios develops in the sac of the
recipient twin because of volume overload and increased fetal urine output.
Oligohydramnios develops in the sac of the donor twin because of hypovolemia and
decreased urine output. Severe oligohydramnios can result in the stuck twin
phenomena in which the twin appears in a fixed position against the uterine wall.
o Moderate TTTS develops later at 24-30 weeks' gestation. Although a fetal size
discrepancy of more than 1.5 weeks' gestation occurs, polyhydramnios and
oligohydramnios do not develop. The donor twin becomes anemic, hypovolemic, and
growth retarded. The recipient twin becomes plethoric, hypervolemic, and
macrosomic. Either twin can develop hydrops fetalis.
o Mild TTTS develops slowly in the third trimester. Polyhydramnios and
oligohydramnios usually do not develop. Hemoglobin concentrations differ by more
than 5g/dL. Twin sizes differ by more than 20%. Polycythemic twins can develop
hyperviscosity syndrome and hyperbilirubinemia after birth.
• Conjoined twins: Incomplete late division of monozygotic twins produces conjoined twins.
Conjoined twins are connected at identical points and are classified according to site of union.
o Thoracopagus - Joined at chest (40%)
o Xiphopagus/omphalopagus - Joined at abdomen (34%)
o Pygopagus - Joined at buttocks (18%)
o Ischiopagus - Joined at ischium (6%)
o Craniopagus - Joined at head (2%)
• Intrauterine growth retardation: Birth weights of twins, triplets, etc. are smaller than weights of
corresponding singletons. However, when combined, birth weights of twins are greater than
weights of corresponding singletons. Most of the deficit of birth weight occurs in the final 8-11
weeks of pregnancy. Average birth weights are similar between twins and singletons until 32
weeks of gestation. Average birth weights are similar between triplets and singletons until 29
weeks of gestation. Birth weight discrepancies of more than 20-25% are considered
discordant. Discordant birth weights occur in 10% of twins. The cause of discordant birth
weights among twins is the difference between each twin's placental surface area or TTTS.
Discordant birth weights among triplets are more common than discordant birth weights
between twins. Approximately 30% of pregnancies with triplets have a birth weight
discordance of more than 25%.
Prognosis:
• The prognosis of infants born from multiple gestations depends upon the complications that
develop. Some studies have reported that the risks of death, chronic lung disease, and grade
III/IV intracranial hemorrhage were similar in twins and singletons. Other studies have
reported a higher prevalence of complications such as necrotizing enterocolitis, retinopathy of
prematurity, and patent ductus arteriosus in infants from multiple gestation versus singletons.