Management of fetal hemolytic disease by cordocentesis; I. prediction of fetal anemia

Article Abstract:

In fetal hemolytic disease, Rh-negative blood type mothers carry Rh-positive blood type fetuses; this results in the destruction of red blood cells of the fetus. The presence of the fetal Rh molecule provokes maternal formation of antibodies against the molecule, and this causes destruction of fetal red blood cells, which carry the Rh molecule. The resulting anemia may be so severe that fetal death occurs. Since the 1960s, fetuses with this disorder have been treated with transfusion after first assessing levels of fetal hemoglobin (the oxygen-carrying protein in red blood cells) indirectly by a nonspecific test for amniotic fluid levels of bilirubin, a hemoglobin breakdown product. An alternative method to measure fetal anemia has been developed, in which fetal blood is directly tested. The effectiveness of the test in evaluating 128 pregnancies with fetal hemolytic disease was evaluated. Of 272 procedures of cordocentesis (sampling of blood from the umbilical vein or artery), 4 percent were associated with fetal bradycardia (slower heartbeat), necessitating an emergency cesarean section at 28 weeks in one case. Very low hematocrit (proportion of blood cells in total blood volume) levels before delivery were strongly predicted by high levels of reticulocytes (immature red blood cells, indicating elevated red blood cell synthesis) or by a score of 3+ or more on a direct Coombs' test, which measures levels of antibodies on red blood cells. Cases were then divided into four risk categories of developing hematocrits less than the 30th percentile (at levels less the lowest 30 percent of pregnancies), based on fetal hematocrit, reticulocyte count, and direct Coombs' test result. Six of 29 cases in the second group, with intermediate risk, required transfusion. In the third and fourth groups, those with the highest risk, transfusions were needed in 80 and 90 percent, respectively. Sampling of umbilical cord blood is associated with greater risks than amniocentesis and should only be performed at experienced regional medical centers. However, the lower number of procedures needed to determine fetal risk of anemia and the good predictive value support the use of umbilical vessel blood sampling for fetal hemolytic disease. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Erythroblastosis fetalis, Cordocentesis

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Diverse maternal and fetal pathology associated with absent diastolic flow in the umbilical artery of high-risk fetuses

Article Abstract:

Since 1978, blood flow in the umbilical cord, which exchanges blood between the developing fetus and the placenta, has been monitored using a technique called Doppler velocimetry (a specialized type of ultrasound test). A rare, abnormal sound pattern caused by absent or reversed diastolic blood flow in the umbilical artery may be associated with fetal stress from reduced delivery of oxygen to the fetus; this may threaten fetal well-being and require premature delivery. The cases of 22 high-risk pregnancies involving abnormal umbilical artery blood flow are described. Karyotyping (analysis of the chromosomes) revealed 10 cases of congenital malformations or abnormal chromosome count (aneuploidy). In 10 other cases, the fetuses were growth retarded due to one of the following factors: maternal hypertension; preeclampsia (a syndrome of hypertension, fluid retention and protein in the urine); maternal heart disease; abnormal levels of alpha-fetoprotein (a fetal protein) in the mother's blood; or twin gestation. For two fetuses, no cause of the umbilical blood flow abnormality could be found. The authors indicate that, once abnormal umbilical artery blood flow has been recognized, karyotyping should be the first procedure used to identify the cause, and then the treatment strategy should be determined based on those results. From this study, it is clear that a wide variety of maternal and fetal complications can contribute to abnormal umbilical artery blood flow. The authors recommend that individualized treatment be selected based upon gestational age, maternal health status, and fetal health status. (Consumer Summary produced by Reliance Medical Information, Inc.)

Case studies, Causes of, Physiological aspects, Birth defects, Chromosome abnormalities, Pregnancy, Complications of, Pregnancy complications, Umbilical arteries

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