In a group of 19 normal pregnant women, plasma lipids were extracted, phospholipids were isolated, and the fatty acid (FA) compositions were measured by capillary gas chromatography. Blood samples were taken at 36 wk, at labor, and at 6 wk postpartum.

The FA profiles showed deficiencies of 6 and 3 FA (indicating the length of the terminal saturated chain), the latter more severe, at all three times.

Mean melting point (MMP) was calculated for each sample as an index of "fluidity" based upon all FA present. MMP varied linearly with total polyunsaturated FA and with double bond index, current measures of "fluidity" and essential FA status. MMP was elevated 9-11C in plasma phospholipids of women during pregnancy and labor and postpartum.

Lactating mothers showed less recovery from the deficiencies than did the nonlactating mothers, but neither approached normal at 6 wk. The changes seen in phospholipid profiles suggest a significant transfer of 3 and 6 polyunsaturated FA from the mother to the fetus.

These FA are essential for normal fetal growth and development; their relative deficiency in maternal circulation suggests that dietary supplementation may be indicated.