Percutaneous fetal umbilical blood sampling: procedure safety and normal fetal hematologic indices

Hemoglobin levels and red blood cell indices in mid-gestational fetuses with beta-thalassemia/HbE, beta-thalassemia trait or Hb E trait and normal fetuses

OBJECTIVE

To compare red blood cell indices among normal, beta-thalassemia trait or hemoglobin (Hb) E trait, and beta-thalassemia/Hb E diseases mid-gestational fetuses.

METHODS

One hundred seventy-five fetuses at risk of beta-thalassemia/Hb E disease undergoing cordocentesis with determination of Hb levels and red blood cell indices at mid-pregnancy were recruited. The fetal diagnoses were based on fetal Hb typing and DNA analysis. The fetuses were divided into three groups: normal, beta-thalassemia trait or Hb E trait, and beta-thalassemia/Hb E disease.

RESULTS

The prevalence of beta-thalassemia/Hb E disease, beta-thalassemia trait or Hb E trait, and normal fetuses was 32.6% (57 cases), 28.6% (50 cases) and 36.6% (64 cases), respectively. Mean Hb levels and red blood cell indices were not significantly different among the three groups of fetuses. However, almost 10% of beta-thalassemia/Hb E fetuses had some degree of anemia. The most anemic fetuses had a β(0) mutation.

CONCLUSION

There is no significant difference in Hb level and red blood cell indices among fetuses at risk of beta-thalassemia/Hb E disease.

Comparison of red blood cell hematology among normal, alpha-thalassemia-1 trait, and hemoglobin Bart's fetuses at mid-pregnancy

The objective of this study was to compare red blood cell indices among normal, alpha-thalassemia-1 trait, and hemoglobin (Hb) Bart's fetuses at mid-pregnancy. A total of 87 pregnancies (88 fetuses) at risk of homozygous alpha-thalassemia-1, who underwent cordocentesis including the measurement of Hb level and red blood cell indices of fetuses at 18-22 weeks of gestation at Maharaj Nakorn Chiang Mai Hospital, were recruited into this study. The final outcome was based on the fetal DNA analysis using PCR technique for SEA type alpha-thalassemia-1. Fetuses were divided into three groups: normal, alpha-thalassemia-1 trait, and homozygous alpha-thalassemia-1 (Hb Bart's disease). The mean gestational age of the 87 pregnant women recruited into the study was 18.7 +/- 0.8 weeks. According to the DNA analysis, the incidence of Hb Bart's disease, alpha-thalassemia-1 trait, and normal fetuses were 29.5%, 45.5%, and 25%, respectively. The mean Hb level, mean corpuscular volume, mean corpuscular Hb, and mean cell Hb concentration were significantly different in all three groups of fetuses. Moreover, these differences were also found among fetuses with the alpha-thalassemia-1 trait and those that were normal. Ninety-two percent of fetuses with Hb Bart's disease had some degree of anemia at mid-pregnancy. However, two Hb Bart's fetuses did not have anemia. Furthermore, two fetuses in the alpha-thalassemia-1 trait group were mildly anemic, but most (95%) were not. There is a highly significant difference in red blood cell indices among normal, alpha-thalassemia-1 trait, and Hb Bart's fetuses, and most fetuses with Hb Bart's disease have some degree of anemia from mid-pregnancy.

Prediction of fetal anemia with Doppler measurement of the middle cerebral artery peak systolic velocity in pregnancies complicated by maternal blood group alloimmunization or parvovirus B19 infection

OBJECTIVES

To confirm the relationship between the middle cerebral artery peak systolic velocity (MCA PSV) and hemoglobin values in fetuses at risk for anemia (due to maternal blood group alloimmunization or parvovirus B19 infection) and to investigate the clinical value of this method in the management of these pregnancies regardless of previous transfusions.

SUBJECTS AND METHODS

Forty singleton pregnancies, 30 affected by alloimmunization and 10 by intrauterine parvovirus B19 infection, were referred to our tertiary center between 1998 and 2000. All cases underwent Doppler measurement of the MCA PSV immediately before fetal blood sampling and just before and after intrauterine transfusion. Hemoglobin determination was always performed after diagnostic cordocentesis, before starting and after terminating fetal transfusion.

RESULTS

Overall, we performed 165 fetal blood samplings (hemoglobin values) and obtained 165 corresponding MCA PSV values, 140 in pregnancies complicated by red-cell alloimmunization and 25 by parvovirus B19 infection. In order to adjust for the effect of gestational age on the measurements, the data were expressed in multiples of the median (MoM). We found a good correlation between MCA PSV MoM and Hb MoM in both groups (alloimmunization, r2 = 0.6; y = 2.21 - 1.41 x + 0.24 x 2; parvovirus infection, r2 = 0.68; y = 2.09 - 0.58 x - 0.16 x 2). The reduction of post-transfusion MCA PSV values was statistically significant ( P < 0.0001). Using a threshold of 1.29 for MoM PSV, the sensitivity and the specificity of MCA pulsatility indices on pretransfusion values in predicting any degree of fetal anemia (Hb < or = 0.84 MoM) were 73.1% and 81.5% in the alloimmunization group and 100% and 100% in the parvovirus infection group, respectively.

CONCLUSION

We can confirm the presence of an inverse correlation between MCA PSV measurements and hemoglobin values in fetuses at risk for anemia due to maternal blood group alloimmunization and fetal parvovirus B19 infection. The MCA PSV is a reliable method for the prediction of anemia not only in fetuses before the first intrauterine transfusion, but also in those which have undergone one or more transfusions, with good sensitivity and specificity in both groups of fetuses at risk.

Risk of fetal infection from invasive procedures

Recent technological advances have led to the development of several types of invasive procedures in the fetus principally for the diagnosis and management of fetal disorders. The risk of infection to the fetus related to these procedures needs evaluation. Although there are few reports of fetal infection, proper infection control procedures must be observed because the most common consequence of infection is fetal loss. Fetal blood sampling in the presence of chorioamnionitis is a risk factor that warrants prophylactic antibiotics. Conversely, clinical specimens taken from the fetus in the absence of chorioamnionitis are more likely to become contaminated with maternal skin flora, and a positive fetal blood culture is not necessarily significant. There is probably a small but finite risk of transmission of maternal viral infections such as human immunodeficiency virus, hepatitis B and C, cytomegalovirus and herpes simplex during invasive procedures. Obstetric departments undertaking invasive fetal diagnosis and treatment must have an adequate policy for infection control procedures.

Complications of fetal blood sampling

To examine the incidence and significance of complications related to percutaneous fetal blood sampling, we reviewed all the articles published in the English literature on this procedure. Risks of complications and adverse outcomes depend mainly on the gestational age at the time of the procedure, the operator's experience, and the indication for the procedure. To determine the incidence of fetal losses, we pooled the data from series with > 100 cases. After exclusion of cases where some fetal pathologic condition was present, we determined the incidence of adverse outcomes in a low-risk population. In this population fetal blood sampling performed by an experienced operator carries about a 1.4% risk of fetal loss before 28 weeks' gestation and a 1.4% risk of perinatal death (after 28 weeks).

Percutaneous umbilical blood sampling: results from a multicenter collaborative registry. The Western Collaborative Perinatal Group

Percutaneous umbilical blood sampling has become an important diagnostic tool in the evaluation of fetal health. Although recent reports have established the safety of this procedure, most have arisen from single centers with extensive experience. The Western Perinatal Collaborative Group has maintained a continuous registry of percutaneous umbilical blood sampling performed at the 13 member institutions for the years 1986 through 1990. During this period 302 procedures were performed. Primary indications for percutaneous umbilical blood sampling included Rh and non-Rh isoimmunization, intrauterine growth retardation, nonimmune hydrops, fetal anomalies, immune thrombocytopenia purpura, and rapid fetal chromosome analysis. Percutaneous umbilical blood sampling was successfully performed in 93.7% of cases with a sample withdrawn by a single puncture in 80.5% of attempts. In the majority of cases a 22-gauge needle was used. Postprocedural fetal death resulted in six cases (2.1%) and was most often associated with fetal anomalies or an abnormal karyotype. In conclusion, evaluation of the fetal state by percutaneous umbilical blood sampling is a safe and easily performed procedure, as demonstrated by a collaborative multicenter study.

The association between fetal karyotype and mean corpuscular volume

To determine whether elevated fetal mean corpuscular volume is characteristic of a chromosome abnormality or fetal disease, 22 fetuses with chromosome abnormalities, 31 with uteroplacental insufficiency, 50 undergoing their first cordocentesis for hemolytic disease, and 50 control fetuses were identified. Chromosomally abnormal fetuses had a significantly higher mean corpuscular volume than the control fetuses. Among fetuses with chromosome abnormalities, the mean corpuscular volume for trisomic or triploid fetuses was significantly higher than for fetuses with other chromosome abnormalities. An elevated mean corpuscular volume was also associated with uteroplacental insufficiency, intrauterine growth retardation, and hemolytic disease. It correlated significantly with gestational age (p less than 0.002 in all cases) in all groups except trisomy or triploidy. In addition, it correlated with hematocrit in the hemolytic disease group (r = -0.60, p less than 0.0001) and with PO2 in fetuses with intrauterine growth retardation (r = -0.43, p = 0.005) from all causes including uteroplacental insufficiency. Trisomic or triploid fetuses showed no such relationships and therefore appear to have escaped the normal control mechanisms for erythropoiesis. One in 12 fetuses with an elevated mean corpuscular volume had trisomy or triploidy, whereas no fetus with trisomy or triploidy had a normal mean corpuscular volume. Thus an unexpectedly elevated fetal mean corpuscular volume in a patient undergoing cordocentesis for reasons other than evaluation of fetal chromosomes would appear to warrant further karyotypic analysis.

Detection of fetal blood contamination by amniotic fluid obtained during cordocentesis

When a fetal blood sample is obtained by cordocentesis it is important to know whether the sample is diluted with amniotic fluid. This study was designed to assess whether contaminated fetal blood samples could be discriminated from noncontaminated ones by the ferning test, and if so what is the minimum dilution ratio of amniotic fluid/fetal blood that is detectable. Fetal blood samples were diluted with amniotic fluid and were tested for ferning under the microscope after the plasma was separated from the cells. At a dilution ratio of 0.2 ml of amniotic fluid to 1 ml of fetal blood, 30% of the samples tested positive for ferning. A rate of 100% detection of ferning was achieved at a dilution ratio of 0.6:1. In conclusion, screening fetal blood samples for ferning can detect amniotic fluid contamination. The sensitivity of the test for ferning depends on the dilution ratio. The test cannot assess how much amniotic fluid was added to the blood sample.

Flow velocity waveforms of the vascular system in the anemic fetus before and after intravascular transfusion for severe red blood cell alloimmunization

Sixteen intravascular transfusions were performed in 16 anemic human fetuses. To investigate the status of the vascular system with Doppler ultrasonography before and after correction of anemia, pulsatility index values were obtained for the flow velocity waveforms of the middle cerebral artery, internal carotid artery, anterior cerebral artery, thoracic aorta, abdominal aorta, renal artery, femoral artery, and umbilical artery before and the day after the correction of anemia. The fetuses were divided into two groups: (1) fetuses with a hematocrit level between 2 and 4 SDs below the normal mean value for gestational age and (2) fetuses with a hematocrit value less than 4 SDs below the normal mean value for gestational age. No significant differences were observed in the pulsatility index values of the vessels studied before and after correction of anemia in both groups of fetuses. These data suggest that the pulsatility index cannot be used as an indicator of fetal anemia at the hematocrit values studied.

Percutaneous umbilical blood sampling

Percutaneous umbilical blood sampling (PUBS), also called cordocentesis, is a newly introduced technique that enables blood samples to be obtained from the fetus in utero for a variety of conditions. The major applications are for the diagnosis of fetal infections, karyotype analysis, fetal growth retardation, diagnosis of hematologic conditions, and metabolic evaluation. This procedure is gaining in popularity, since it provides direct information on fetal blood status. It can be applied to therapeutic manipulations such as in utero transfusions or drug administration. The procedure is remarkably safe and has few technical problems. The applicability of its use in the assessment of fetal thrombocytopenia is also discussed in detail.

Prenatal diagnosis of thrombocytopenia absent radius syndrome by ultrasound and cordocentesis

The prenatal diagnosis of thrombocytopenia absent radius (TAR) syndrome, utilizing ultrasound and cordocentesis, is described. To our knowledge, this represents the first prenatal diagnosis of this condition in an index case. The diagnostic evaluation of a fetus with upper extremity limb reduction defects is discussed.

Perinatal diagnosis of passive ITP: use of percutaneous umbilical blood sampling (PUBS)

Fetal blood samples can be obtained in utero by direct sampling of the umbilical cord vessels, using an ultrasound guided technique termed percutaneous umbilical sampling (PUBS). This procedure is being used more frequently in high risk pregnancies to obtain direct fetal laboratory data. In specialized centers, with trained personnel, the technique can be used with a high degree of safety and efficiency. Direct access to the fetal circulation can also allow an accurate determination of the fetal platelet count in cases of suspected fetal thrombocytopenia. The technique may be used to plan appropriate clinical management of maternal ITP as well as to diagnose the presence of fetal alloimmune thrombocytopenia. A logical strategy for obstetric management and evaluation of fetal risk can be planned. The procedure also has the potential to allow direct fetal treatment as has been the case in the management of severe fetal anemia.

Percutaneous umbilical blood sampling

Percutaneous umbilical blood sampling (PUBS) provides a new and exciting method for assessment and management of certain fetal disorders. This procedure offers direct access to the fetal circulation for obtaining blood samples or for transfusing the fetus in utero. Although investigational, PUBS offers treatment approaches that were not previously available. This ability to treat the fetus in utero can prolong pregnancy, resulting in decreased prematurity and mortality rates for infants with erythroblastosis fetalis. This article describes the PUBS procedure and the indications for PUBS and discusses the nursing implications associated with the care of women undergoing PUBS.