Enrichment of NRBC in maternal blood: a more feasible method for noninvasive prenatal diagnosis.

OBJECTIVE

To assess the efficiency and reliability of the separation of fetal nucleated red blood cells (NRBCs) using the galactose-specific lectin method, we counted the number of NRBCs in the blood of pregnant women at various gestational ages, as well as after amniocentesis and termination.

METHOD

Peripheral blood samples were obtained from (1) 22 singleton pregnant women (between 9 and 34 weeks of gestation) and from 23 women who underwent termination (between 6 and 19 weeks of gestation). To determine whether amniocentesis influences numbers of NRBCs, five samples were obtained (2) before and after the procedure. NRBC enrichment was initially performed using density gradients and subsequently using galactose-specific lectin. The cells were then stained with May-Gruenwald Giemsa (MGG) and counted under a light microscope.

RESULTS

NRBCs were found in all samples, ranging from 1 to 82 (median = 12.5 cells/sample). The multiples of the median (MoM) conversion of the number of cells revealed a raise of 1.66-fold (0.12-6.64) in post-termination samples compared with the control value of 1.00 MoM (0.11-6.92; p = 0.036). The postamniocentesis increase was, instead, 1.11-fold (0.17-4.02), which did not reach statistical significance.

CONCLUSION

All blood samples tested contained NRBCs. Samples obtained after termination yielded more cells than those obtained from women whose pregnancies were going on normally. The number of NRBCs in post-termination samples after MoM conversion differed significantly from those in controls. Although separation of NRBCs was not feasible due to extremely low numbers, our results indicated that NRBCs are detectable in all blood samples from normal pregnant women.