Anemia of Prematurity - Portal Neonatal

o Fibroelastosis may be an isolated abnormality; however, fibroelastosis more commonly
represents an endocardial response to chronic fetal myocardial stress. Prenatal
detection of a cardiac defect should always trigger a careful search for other
malformations, and karyotyping should be performed in all such fetuses. Arteriovenous
malformations (AVMs) are often cited causes of hydrops; they are listed individually in
Table 2.
• Impaired right-heart filling is also an important cause of hydrops. Although uncommon,
umbilical or vena caval thromboses are noted, since they theoretically may be correctable if
diagnosed early enough. Conversely, tumor compression is a frequently reported cause of
hydrops. Several of these masses involve lymphatic malformation and/or obstruction; cystic
hygroma is a particularly important example.
• Prenatal closure of the foramen ovale or ductus arteriosus prematurely converts the
(parallel) fetal circulation to a (serial) postnatal circulation; associated problems are
obvious.
o Most recorded instances of premature ductal closure are iatrogenic, related to
maternal administration of indomethacin or sodium diclofenac.
o Several instances of idiopathic arterial calcification with hydrops have been
reported. In one such incident, fetal serum calcium levels were elevated, and a
possible association with Williams syndrome was suggested. In 3 other cases,
lysosomal storage diseases were present (Gaucher, sialidosis, galactosialidosis).
No associations were noted in 4 cases. Hydropic recipients of twin-twin transfusion
who survive usually also have pulmonary artery calcification.
• Fetal supraventricular tachycardias are important causes of hydrops because they can be
diagnosed accurately by cardiac imaging in early pregnancy, they may be treated
effectively before hydrops develops, and, since associated malformations or syndromes are
rare, they have anticipated good outcomes. Whether an AV block is present (atrial flutter)
or not (tachyarrhythmia), survival rates of 85-95% are typical, and neurodevelopmental
outcome usually is normal. The condition is more common in males than in females (2:1),
and hypoglycemia is a commonly associated finding, at least after birth. Clinical experience
and animal model studies indicate that hydrops occurs with sustained cardiac rates of less
than 220-230 beats per minute (bpm) and that the risk is related directly to the degree of
prematurity.
• Congenital heart block (CHB) is also often associated with hydrops. Diagnosis is made
using cardiac imaging; rates are always less than 90 bpm and usually less than 65 bpm.
Approximately two thirds to three fourths occur in pregnancies complicated by maternal
collagen disease. Maternal IgG antinuclear antibodies cross the placenta and attack fetal
collagen in the conduction bundle.
o Why some fetuses develop CHB and some do not is unclear; however, an
association with human leukocyte antigen (HLA) types (HLA-DR3, among others)
has been suggested.
o Treatment with a variety of drugs has generally been unsuccessful, as has fetal
surgery for pacing. Recent evidence suggests corticosteroid therapy may be of
benefit.
• Virtually all of the remaining babies, whose mothers have no collagen disorder, have
serious, complicated, cardiac structural defects. The most common lesions are AV canal
and/or endocardial cushion defects, transposition of the great vessels, and other
isomerisms. Outcomes for these babies are grim. Mortality is 25-35% if cardiac structure is
normal; many survivors require neonatal surgery for pacing, and no information is available
on long-term outlooks. Since the cardiac structural abnormalities are so serious and
complex, mortality and morbidity are much higher if cardiac anomalies are present.
• The immature fetus is particularly susceptible to overwhelming viral and bacterial infection.
Those agents, which do not kill quickly, may cause smoldering generalized infections with
myocarditis, suppressed erythropoiesis and myelopoiesis, hemolysis, and hepatitis. Such
infections may lead to hydrops fetalis. Those agents reported to be causative, to date, are
listed in Table 3. This list will change with time as other agents, yet to be unidentified, are
demonstrated to cause hydrops.