Anemia of Prematurity - Portal Neonatal

however, AFP levels are similar in babies with Turner syndrome with or without
hydrops. Use of AFP screening as an index of fetal aplastic crisis in maternal
Parvovirus infection has been recommended but is of dubious value, since several
fetal deaths have been observed with AFP levels within reference range. The precise
diagnostic value of AFP screening is uncertain, since definitive studies are not
available.
� Low levels of unconjugated estriol (uE3) have been found in one hydropic baby with
Smith-Lemli-Opitz syndrome, but the test has not demonstrated value in distinguishing
between babies with or without hydrops, and normal levels have been observed in
several hydropic deaths.
� Human chorionic gonadotropin levels have been reported as significantly elevated in
hydrops with sacrococcygeal teratoma, choriocarcinoma, Parvovirus, Turner
syndrome, and Down syndrome; however, these levels have also been normal in
several hydropic fetal deaths related to Parvovirus.
� In a single study, inhibin-A levels were elevated markedly in 12 fetuses with Turner
syndrome with hydrops and were reduced significantly in those fetuses without
hydrops.
� Maternal serum IgG placental alkaline phosphatase levels are increased with fetal
hydrops; currently, clinical utility of this finding is untested.
• Direct invasive sampling studies of fetal AF or placental tissues or fluids have demonstrated
value for definitive diagnosis, monitoring of treatment efficacy, and accurate prognosis in a
number of conditions associated with hydrops.
o Elevated levels of AF bilirubin, as measured by the spectrophotometric extrapolation
technique first described by Liley, have been demonstrated to be highly sensitive
predictors of the severity of fetal anemia due to isoimmunization.
� Specificity is somewhat less, since alpha-feto bilirubin may also be elevated due to
maternal hemoglobinopathy or hepatitis and in association with impaired fetal
swallowing due to fetal gastrointestinal obstruction and a number of fetal central
nervous system disorders.
� Recent reports have suggested the use of sonographic methods to detect fetal
anemia; however, routine use of such noninvasive methods is not justified in the
absence of definitive evidence of their superior sensitivity and specificity, at less risk,
when compared with the standard proven method of AF bilirubin analysis.
o Direct enzyme assays or biochemical analyses of measurements of levels of specific
metabolic products may be indicated in the pregnancy at risk of hydrops because of inborn
errors of metabolism.
� Such studies may use samples from the mother and father (red cells, serum, urine,
tissue), fetus (skin fibroblast cultures or leukocytes from AF, fetal red cells, white cells,
serum samples from direct cordocentesis, serous effusions), placenta (chorionic
villous sampling, placental biopsy), or AF.
� Examples include biochemical analyses of urine or AF for abnormal oligosaccharide,
mucopolysaccharide, and sphingolipid metabolites when lysosomal disorders are
suspected or determination of AF 7-dehydrocholesterol reductase if history and
findings suggest Smith-Lemli-Opitz syndrome.
o Fetal serum endothelin levels are elevated more than 2-fold in recipients; however, these
levels are normal in donors with twin-twin transfusion syndrome. Endothelin levels were
related to presence of and severity of hydrops in these cases. Changes in fetal serum liver
enzymes, particularly alanine transaminase and glutamyl transpeptidase, have been
demonstrated to occur following correction of the anemia by fetal transfusion. Whether or
not these observations may be of diagnostic or prognostic use is currently untested.
o Direct fetal diagnostic studies for Parvovirus include histologic staining methods (RBC),
digoxigenin-labeled B19. DNA probe (PCR), and avidin-biotin complex
immunohistochemical and immunofluorescent studies, among others. Currently, PCR
methods appear to be best, although definitive studies providing sensitivity and specificity
are not available.