Intrahepatic cholestasis of pregnancy (ICP) is associated with increased stillbirth risk. This study aimed to assess the relationship between bile acid concentrations and fetal cardiac dysfunction in ICP with or without ursodeoxycholic acid (UDCA) treatment.Bile acid profiles and NT-proBNP, a marker of ventricular dysfunction, were assayed in umbilical venous serum from 15 controls and 76 ICP cases (36 untreated, 40 UDCA-treated). Fetal ECG traces were obtained from 43 controls and 48 ICP cases (26 untreated, 22 UDCA-treated). PR interval length and heart rate variability parameters (RMSSD, SDNN) were measured in two behavioural states (quiet and active sleep). Partial correlation coefficients (r) and median [IQR] are reported.In untreated ICP, fetal total serum bile acids (TSBA, r=0.49, p=0.019), their hydrophobicity index (r=0.20, p=0.039), glycocholate (r=0.56, p=0.007) and taurocholate (r=0.44, p=0.039) positively correlated with fetal NT-proBNP. Maternal TSBA (r=0.40, p=0.026) and alanine aminotransferase (r=0.40, p=0.046) also positively correlated with fetal NT-proBNP. No significant correlations to NT-proBNP were observed in the UDCA-treated cohort. Fetal PR interval length positively correlated with maternal TSBA in untreated (r=0.46, p=0.027) and UDCA-treated ICP (r=0.54, p=0.026). Fetal RMSSD in active sleep (9.6 [8.8,11.3] vs. 8.7 [7.6,9.6] ms, p=0.028) and SDNN in quiet sleep (11.0 [9.5,14.9] vs. 7.9 [5.1,9.7] ms, p=0.013) and active sleep (25.4 [21.0,32.4] vs. 18.2 [14.7,25.7] ms, p=0.003) were significantly higher in untreated ICP cases than controls. Heart rate variability values in UDCA-treated cases did not differ to controls.Elevated fetal and maternal serum bile acid concentrations in untreated ICP are associated with an abnormal fetal cardiac phenotype characterised by increased NT-proBNP concentration, PR interval length and heart rate variability. UDCA treatment partially attenuates this phenotype.