Nucleated red blood cells in human fetal scalp capillary blood samples: a feasibility study

Elevated umbilical cord nucleated red blood cell (NRBC) counts have been suggested as a predictor of adverse perinatal outcome. We sought to evaluate the feasibility of obtaining fetal scalp capillary blood NRBC counts during labor and to assess their correlation with umbilical cord NRBC counts.

Fetal scalp capillary blood specimens were prospectively collected in laboring patients who underwent scalp sampling because of the presence of an abnormal fetal heart rate pattern. Matched umbilical cord blood samples were collected immediately after birth. Outcome measures were the feasibility of obtaining fetal scalp NRBC counts and their correlation with umbilical cord NRBC counts.

Thirteen term singleton pregnancies formed the study population. In four patients, fetal scalp capillary blood sampling was performed twice. Of the attempts to evaluate fetal scalp capillary samples for NRBC counts, 16 out of 17 (94.1%) were successful. The mean fetal scalp capillary blood NRBC count per 100 white blood cells was 12.6 +/- 7.6 (+/- SD). Umbilical cord mixed, venous and arterial NRBC counts were 15.5 +/- 8.8, 13.4 +/- 10.7 and 12.6 +/- 10.7, with p = 0.09, p = 0.59 and p = 0.68, respectively, when compared to the corresponding scalp sample. The Spearman rank correlation between fetal scalp capillary samples and umbilical cord mixed, venous and arterial NRBC counts were r = 0.86, r = 0.92 and r = 0.95, respectively, with all p values < 0.001.

Previous studies have established the clinical utility of umbilical cord NRBC counts. Our study demonstrated that it was possible to obtain NRBC counts from a fetal scalp capillary sample and that these counts correlated highly with umbilical cord NRBC counts. Future studies are needed to evaluate fetal scalp NRBC counts as a predictor of perinatal outcome.