Beta-human chorionic gonadotropin, progesterone, and aqueous dynamics during pregnancy.

OBJECTIVE: To determine whether the altered hormonal milieu of pregnancy is associated with changes in the dynamics of aqueous humor formation and drainage.
DESIGN: Nineteen women were studied during each trimester of a single pregnancy and post partum. Measures of aqueous dynamics included intraocular pressure, aqueous flow, facility of outflow, aqueous flare, and corneal thickness.
RESULTS: Pregnancy was associated with relatively lower intraocular pressure, reduced aqueous flare, increased corneal thickness, and increased aqueous outflow facility. Aqueous flow was unchanged. The progesterone level increased during pregnancy and decreased during the postpartum period. The beta-human chorionic gonadotropin level was highest during the first trimester. The progesterone level, but not the beta-human chorionic gonadotropin level, was correlated with intraocular pressure, aqueous flare, and corneal thickness. The change in aqueous outflow facility that accompanied pregnancy could not be correlated directly to changes in beta-human chorionic gonadotropin or progesterone concentrations.
CONCLUSIONS: Aqueous flow remains constant during and after pregnancy, but intraocular pressure decreases during pregnancy due to an increase in the outflow facility. The changes in aqueous dynamics are consistent with the hypothesis that excess progesterone during pregnancy blocks the ocular hypertensive effect of endogenous corticosteroids. However, we were unable to find a statistically significant correlation when a direct comparison between the observed changes in outflow facility and the observed changes in the progesterone level was made, perhaps because of intersubject variability of these changes. The changes in intraocular pressure and outflow facility could have been due to one of many other changes in pregnancy that were not measured.