THE COMPOSITION OF INDIVIDUAL MOLECULAR-SPECIES OF PLASMA PHOSPHATIDYLCHOLINE IN HUMAN-PREGNANCY

The molecular species composition of plasma phosphatidylcholine (PC) w as measured in sequential blood samples from 13 pregnant women from 16 weeks of gestation to delivery at term. The increased total plasma PC concentration at term was due solely to increased concentrations of i ndividual species containing palmitate (16:0) rather than stearate(18: 0) at the sn-1 position. The specific increase of PC16:0/22:6 concentr ation in mid-gestation suggests that adaptations to maternal hepatic P C metabolism may provide a mechanism to ensure adequate supply of 22:6 (n-3) to the fetus. While cord plasma PC was comparable to liver PC co mposition from three stillborn term infants, the compositions of these tissues differed from maternal plasma PC, which contained significant ly more PC16:0/18:2 and PC18:0/18:2. These results suggest that, altho ugh fetal acquisition of polyunsaturated fatty acids (PUFA) is depende nt on the maternal lipid supply, the detailed composition of fetal pla sma PC may be regulated largely by intrinsic fetal mechanisms such as placental and liver PC metabolism. Similarly, the specific alterations to maternal plasma PC composition in pregnancy, which we postulate ar e associated with the supply of PUFA to the fetus, were substantially independent of variations in maternal dietary lipid nutrition.