The distribution of arachidonic acid in plasma and tissues of patients near term undergoing elective or emergency Caesarean section.

The distribution of arachidonic acid in both the free and the bound state was measured in the maternal circulation, the fetal circulation and tissues within the pregnant uterus in 16 patients undergoing Caesarean section. Half of the patients had an elective Caesarean section and half had a Caesarean section during labour. No differences in arachidonic acid concentrations were found between the maternal or fetal circulations in women having elective Caesarean section and those having a Caesarean section in labour. The total and bound values of arachidonic acid in myometrium were higher in patients undergoing Caesarean section in labour. There was also an increased amount of arachidonic acid when expressed as an arachidonic acid/palmitic acid ratio between the fetal circulation and the maternal circulation, suggesting an active transport mechanism for arachidonic acid across the placenta. Levels of free arachidonic acid were in microgram quantities in both plasma and tissues, suggesting that the availability of free arachidonic acid was not the limiting factor in prostaglandin production.