OBJECTIVE: Our goal was to ascertain whether alterations in β- and α-adrenergic receptor number and function (cyclic adenosine monophosphate production) occur during and after pregnancy. Because the actions of β- and α₂-adrenergic receptors tend to oppose each other, we hypothesized that there might be progressive, possibly reciprocal changes in these receptors during and after pregnancy. STUDY DESIGN: Blood was obtained from 21 women at 10, 20, 30, and 37 weeks of pregnancy and 3 to 4 months post partum. Lymphocyte β- and platelet α₂-adrenergic receptor number and affinity were quantified by radioligand binding studies, and receptor function was assessed by cyclic adenosine monophosphate generation assays. RESULTS: Although there were suggestions of progressive alterations in some of the variables studied, β- and α₂-adrenergic receptor number, affinity, and function did not manifest any statistically significant changes. CONCLUSION: Pregnancy did not produce marked alterations in β-adrenergic receptor or α₂-adrenergic receptor properties.(Am J Obstet Gynecol 1997;177:234-42)