Maternal outcomes:
Bile acid concentrations and itch scores post-randomisation, stratified by baseline characteristics, are shown in Table 1.
Mean trajectories of bile acid concentration grouped by baseline bile acid concentration are shown in Figure 1. Visual inspection shows that bile acid concentrations reduced in women taking UDCA and placebo, most notable in women with baseline bile acid concentrations ≥40 μmol/L, and also seen in women with baseline bile acid concentrations ≥100 μmol/L. In women with baseline bile acid concentrations <40 μmol/L, treatment with UDCA resulted in higher post-randomisation bile acid concentrations compared to placebo (geometric mean ratio 1.19, 95% CI 1.00 to 1.41, p = 0.047). There was no significant increase in women with higher baseline bile acid concentrations (≥40 μmol/L) (geometric mean ratio 1.13, 95% CI 0.81 to 1.58, p = 0.466). A test of interaction showed no significance (p = 0.647). When stratified by a higher threshold (100 μmol/L), in women with baseline bile acid concentrations <100 μmol/L, treatment with UDCA resulted in increased post-randomisation bile acid concentrations (geometric mean ratio 1.19, 95% CI 1.02 to 1.39, p = 0.031). There was no significant difference in women with baseline bile acid concentrations ≥100 μmol/L (geometric mean ratio 0.97, 95% CI 0.48 to 1.96, p = 0.941). A test of interaction showed no significance (p = 0.458).
Mean trajectories of itch score stratified by baseline itch score and baseline bile acid concentration are shown in Figure 2. In women with a high baseline itch score (≥60 mm), treatment with UDCA resulted in a small 6.0 mm decrease in itch score compared to placebo (p = 0.041). There was no evidence of a significant effect of UDCA seen in women with a baseline itch score <60 mm. A test of interaction showed no significance (p = 0.640). There was no difference in change in itch score between women with a high or low baseline bile acid concentration and a test of interaction showed no significance (p = 0.455). Similarly, a test of interaction showed no significance (p = 0.753) in women stratified by a baseline bile acid concentration threshold of 100 μmol/L.
Mean trajectories of bile acid concentration and itch score were further examined, stratified by initial bile acid trajectory either increasing or decreasing, as shown in Figures S2 and S3. Tests of interaction showed no significance for moderation of either post-randomisation bile acid concentrations or post-randomisation itch score.
The relationship between itch score and bile acid concentration for all women at all visits is shown in Figure 3. The adjusted R2 was 0.080.