Serial betamethasone administration: effect on maternal salivary estriol levels

Maternal salivary estriol levels are an indirect measure of fetal adrenal activity, which may be affected by administration of betamethasone. The objective was to compare sequential salivary estriol levels in patients receiving serial betamethasone therapy with those of healthy pregnant patients.

Ten patients at high risk for preterm delivery were asked to obtain salivary specimens before and 1 to 2 days after each administration of weekly betamethasone treatments between 24 and 32 weeks' gestation. These values were compared with those of specimens obtained throughout gestation in healthy women who were not delivered preterm. Unconjugated salivary estriol was measured with a sensitive and specific enzyme-linked immunoassay (Biex, Inc, Dublin, Calif).

The effect of betamethasone on salivary estriol levels did not change with time, showing an average of 23.1% drop from pretreatment to posttreatment levels but rebounding to the same starting level before the next dose. When weekly pretreatment values were looked at across time, the geometric mean of the individual patients' slopes did not differ significantly from no change. The same was true of the posttreatment values. The rate of change with advancing gestation was compared between 182 control subjects and the 10 study subjects. The average change was +8.8% per week in the control subjects and -1.3% per week in the study patients (P =.003).

Maternal administration of betamethasone significantly suppressed salivary estriol levels. These levels returned to pretreatment values each week before the next dose; however, the rise normally associated with advancing gestational age was not observed.