Histamine and ascorbic acid: a survey of women in labor at term and significantly before term.

In ascorbic acid-requiring species (human, guinea pig), elevations of circulating histamine occur as the result of marginal ascorbic acid status. Marginal ascorbic acid status during pregnancy is associated with preeclampsia, abruption, and prematurity. Furthermore, circulating histamine is known to be elevated in these complications perhaps as a result of placental dysfunction which diminishes normal placental histaminase. We hypothesized that women with preeclampsia and premature labor would have elevated histamine and the lowest concentrations of ascorbic acid. Plasma total whole blood histamine and ascorbic acid were surveyed in women in term (T) and preterm (PT) labor. Blood histamine was elevated in PT compared to T labor but so was plasma ascorbate, indicating that marginal ascorbate status does not cause the elevated circulating histamine observed in PT. However, marginal ascorbate status concomitant with reduced placental histaminase may contribute to further increases in circulating histamine and to any pathology which might result from elevated histamine. Regression analysis of histamine on ascorbate for T and PT labor revealed a significant inverse relationship between ascorbate and histamine only in PT labor (p less than 0.027). An unexpected finding was that a history of maternal cigarette smoking, to a degree which resulted in marginal ascorbic acid status, confounded the relationship between ascorbate and circulating histamine in T labor.