Elevated total bile acid levels during late pregnancy are associated with the risk of small-for-gestational-age infants

Background Intrahepatic cholestasis of pregnancy (ICP) is common in pregnant women and is diagnosed by detecting serum total bile acid (TBA) levels. We aimed to investigate the association between serum total bile acid (TBA) levels during late pregnancy and the incidence of small-for-gestational-age (SGA) infants in a Chinese population.Methods The present study was a retrospective cohort study that included 11811 eligible mother-and-singleton-offspring pairs. The correlations between TBA levels and birth sizes, including birth weight, birth length, head circumference and chest circumference, were explored. The relative risk (RR) with 95%CI for SGA infants were estimated among subjects with ICP by multiple logistic regression analysis.Results Serum TBA levels were inversely linked with birth sizes. According to TBA levels, 11120 pregnant women were controls, 563 mild ICP, and 128 severe ICP. Birth sizes in ICP groups were lower than control group, and were the lowest in severe ICP group. Further analysis showed that 24.51% neonates were SGA infants among subjects with mild ICP (adjusted RR: 3.44; 95%CI: 2.72, 4.34) and 39.06% among subjects with severe ICP (adjusted RR: 6.54; 95%CI: 4.27, 10.02), higher than 7.39% among controls. For adjusted models, linear regression analysis showed that each 1μmol/L increase in TBA levels was associated with 11.1g (95%CI: -12.7, -9.5) decrease in birth weight, 0.045cm (95%CI: -0.053, -0.036) decrease in birth length, 0.034cm (95%CI: -0.040, -0.028) decrease in head circumference, and 0.041cm (95%CI: -0.047, -0.034) decrease in chest circumference, respectively.Conclusion Elevated TBA levels during late pregnancy are associated with an increased risk of SGA infants.