Maternal platelet size as a marker for fetal trisomies 18 and 13.

Maternal and fetal platelet size and glycoprotein expression were measured in 14 pregnancies complicated by fetal aneuploidy between 20 and 24 weeks' gestation. Flow cytometry was used to determine platelet size and surface glycoprotein Ib (GPIb) and GPIIIa expression both before and after stimulation with adenosine diphosphate (ADP). The data were compared with results obtained from 35 normal paired maternal and fetal controls. In fetuses affected with trisomies 18 and 13, but not trisomy 21, the maternal and fetal platelet sizes were significantly higher than those of the normal controls. Furthermore, the increase in fetal platelet size was significantly associated with the increase in maternal platelet size. Increase in maternal platelet size may be of potential value as a marker for fetal trisomies 18 and 13.

Blood transferrin receptor expression in chromosomally abnormal fetuses.

In a cross-sectional study of 13 chromosomally abnormal fetuses, umbilical venous blood was obtained by cordocentesis at 17-32 weeks' gestation. Fetal blood transferrin receptor (CD71) expression (mean = 79.8 per cent, range = 60-98 per cent) and nucleated red cell count (mean = 10.4 x 10(9) per 1, range = 1.0-25.0 x 10(9) per 1) were significantly higher than the appropriate normal mean for gestation (z = 3.92, P < 0.0001 and z = 3.69, P < 0.001, respectively). These haematological changes in chromosomally abnormal fetuses would facilitate their prenatal diagnosis by analysis of fetal nucleated red blood cells isolated from the maternal circulation on the basis of CD71 expression.

Platelet size and glycoprotein Ib and IIIa expression in normal fetal and maternal blood.

OBJECTIVE: Our purpose was to study platelet size and surface glycoprotein expression in normal fetal and maternal blood throughout pregnancy. STUDY DESIGN: A cross-sectional study was performed at the Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London. Fetal and maternal blood samples were obtained from uncomplicated pregnancies at 8 to 42 weeks' gestation (n = 101 and n = 117, respectively) and from 30 nonpregnant controls. Flow cytometry was used to determine platelet size and glycoprotein Ib and IIIa expression both before and after stimulation with adenosine diphosphate. RESULTS: Mean platelet size in both fetal and maternal blood was significantly lower than that of nonpregnant controls and decreased with advancing gestation. The surface density of glycoprotein Ib in maternal and fetal platelets was significantly lower than in nonpregnant controls but did not change with gestation. Adenosine diphosphate stimulation of maternal platelets resulted in increased percentage expression and surface density of all glycoproteins, whereas stimulation of control platelets resulted in increased surface density of glycoprotein Ib and percentage expression of glycoprotein IIIa. Adenosine diphosphate stimulation of fetal platelets resulted in increased surface density of glycoprotein Ib and IIIa. CONCLUSION: Pregnancy is associated with increased thrombocytopoiesis in both the mother and fetus. Maternal platelet glycoprotein expression and responsiveness to adenosine diphosphate stimulation is increased. Fetal platelets are phenotypically mature from at least 12 weeks' gestation and respond in an adultlike fashion to stimulation with adenosine diphosphate.

Fetal blood mononuclear cell division in normal and pathological pregnancies.

Fetal blood mononuclear cell division was measured using flow cytometry in 53 normal pregnancies and 51 pathological pregnancies complicated either by anaemia due to red blood cell isoimmunisation (RCI: n = 21), intrauterine growth retardation (SGA: n = 13) or abnormal karyotype (n = 17). In normal pregnancy, mononuclear cell division rates decreased with gestational age from a mean of 1.8% at 18 weeks to 1% at 40 weeks. Furthermore, there was a significant association between cell division and erythroblast count. The rates of cell division and erythroblast count were significantly increased in the chromosomally abnormal fetuses, and significantly decreased in the transfused RCI fetuses compared to the controls. Although the erythroblast count was elevated in the SGA fetuses, the mononuclear cell division was not significantly different from the controls. Fetal blood mononuclear cell division is elevated in early pregnancy and in chromosomally abnormal fetuses, probably as a consequence of increased numbers of circulating haemopoietic precursors. Mononuclear cell division is decreased in transfused RCI fetuses as a consequence of suppressed erythropoiesis. In SGA fetuses, despite the increased erythropoietic stimulation and erythroblastosis, cell division is not increased.