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 μl of fetal plasma. Determination of apolipoproteins in fetal blood obtained by fetoscopy thus may provide a method for the prenatal diagnosis of congenital apolipoprotein deficiences.