Apolipoproteins in human fetal blood and amniotic fluid in mid-trimester pregnancy

To examine the potential for prenatal diagnosis of genetic lipoprotein metabolic defects (e.g. abetalipoproteinemia. Tangier disease) we determined the normal concentrations of apolipoproteins (apo) A-I, A-II, B, and E in mid-trimester amniotic fluid and fetal plasma. The concentrations of apo A-I and apo A-II in amniotic fluid were 1--2 per cent of the respective levels in the mother's plasma, whereas apo B and apo E were undetectable in amniotic fluid. In contrast to amniotic fluid, all four apolipoproteins were detectable in fetal plasma, and the levels of apo A-I, apo B and apo E were in the range observed in the mothers: 160.2 +/- 103.1, 59.8 +/- 35.7 and 5.7 +/- 3.5 mg/dl respectively (mean +/- SD, n = 13). The fetal plasma level of apo A-II (28.3 +/- 12.4 mg/dl) was two-thirds that observed in the mother's plasma. The normal levels of these apolipoproteins in fetal plasma are well above the sensitivity of the methods, and their quantification requires only 10--20 microliters of fetal plasma. Determination of apolipoproteins in fetal blood obtained by fetoscopy thus may provide a method for the prenatal diagnosis of congenital apolipoprotein deficiencies.