Estrogens' effect on the liver has been studied extensively. The active transport of biliary components in the canaliculi is impaired by estrogen (13). The pregnant state can cause some changes in bile acid production and secretion, presumably due to the higher levels of estrogen, but also because of progesterone's effect on GI motility. This can lead to a mild subclinical cholestasis. Studies have shown conflicting evidence as to whether there is an increase in bile acid levels during pregnancy. As estrogen increases are known to induce a cholestasis, and urobilinogen levels increase in cholestasis, our hypothesis is that the increase in estrogen levels within the last week of pregnancy may slow the clearance of bile even further yielding the rise in urobilinogen levels noticed on routine dipstick.