Little is known about the effects on the fetus of ursodeoxycholic acid (UDCA) treatment for intrahepatic cholestasis of pregnancy (ICP). Twenty ICP patients were given UDCA at 1.5 to 2 g/d, to our knowledge the highest dosage yet reported. Effects were evaluated on conjugated bile acids (BA) in amniotic fluid (15 of 20 patients) and umbilical cord serum obtained at delivery (20 of 22 newborns), as compared with 10 untreated patients (amniotic fluid, 9 of 10 patients; cord serum, 9 of 10 newborns). Liver function tests, serum BA and UDCA were evaluated on enrollment and then weekly until 1 week after delivery. Maternal serum conjugated cholic (CCA) and chenodeoxycholic (CCDCA) acids levels fell (18.5 +/- 1.9 to 10.5 +/- 1.9 micromol/L, and 5.8 +/- 0.8 to 2.97 +/- 0.7 micromol/L, respectively [P <.01]) in treated patients, and remained unaffected (20.0 +/- 3.1 vs. 20.3 +/- 2.3, and 5.6 +/- 0.6 vs. 5.4 +/- 0.5, respectively [P = not significant]) in untreated ones. Serum conjugated UDCA levels rose to 16.5 +/- 1.8 micromol/L (P<.001). Median values of CCA and CCDCA in amniotic fluid around delivery were 4.9 +/- 12.4 and 4.8 +/- 7.7 micromol/L, respectively, in treated patients, as against 17.9 +/- 27.5 and 18.5 +/- 20.9 micromol/L in untreated ones. In treated mothers, CCA and CCDCA concentrations in cord blood were 6.0 +/- 0.9 and 5.2 +/- 0.95 micromol/L, respectively, as against 21.9 +/- 5.6 and 18.9 +/- 2.1 micromol/L in untreated ones. In treated patients, median UDCA values in amniotic fluid and cord blood were 0.8 +/- 2.4 and 0.9 +/- 0.14 micromol/L, respectively. We conclude that increasing the dose of UDCA more effectively controls ICP and improves maternal clinical outcome after delivery.