Source of prostaglandin precursor in human fetal membranes: arachidonic acid content of amnion and chorion laeve in diamnionic-dichorionic twin placentas.

The lipids of the avascular human amnion and chorion laeve are known to be enriched in the essential fatty acid arachidonic acid, the obligate precursor of prostaglandins of the 2-series. The present investigation was conducted to evaluate the source of arachidonic acid that is present in human fetal membranes. To do so we determined the arachidonic acid content of the lipid fractions of amnion and chorion laeve tissues from diamnionic-dichorionic twin placentas. We found that the arachidonic acid content of amnion from twin placentas was similar to that of amnion from singleton placentas irrespective of the site of amnion sampling. However, the same was not true of chorion laeve of diamnionic-dichorionic twin placentas. The arachidonic acid content of chorion laeve that was contiguous to the chorion laeve of its twin was strikingly reduced compared to that of chorion laeve contiguous to decidua vera obtained from either singleton or twin placentas. We conclude that the arachidonic acid in amnion is derived primarily from essential fatty acids in the amniotic fluid. However, the arachidonic acid in chorion laeve may be derived from essential fatty acid in the amniotic fluid as well as in maternal plasma by way of the decidua vera.