Intrahepatic cholestasis of pregnancy (ICP) occurs in the second and third trimester, and is characterized by pruritus and an elevation in serum bile acid concentrations. The major clinical features, diagnosis and treatment of intrahepatic cholestasis of pregnancy will be reviewed here. A general approach to the pregnant woman who develops liver disease is presented elsewhere. (See "Approach to liver disease occurring during pregnancy".)
The incidence of ICP has varied widely in various reports (ranging from 0.1 to 15.6 percent), for reasons that are incompletely understood . Geographic variations in the rates of the disease may reflect differences in susceptibility between ethnic groups. The incidence of ICP is increased in Bolivia, and is highest among the Araucanos Indians in Chile . A study from Sweden that included 1.2 million births between 1997 and 2009 estimated the incidence to be 0.5 percent of all deliveries . In reports from the United States, the incidence rates have varied from 0.32 percent in Bridgeport Hospital, Connecticut , to 5.6 percent in a primarily Latin population in Los Angeles . For unknown reasons the disease is seen more commonly in the colder months in Chile and Scandinavia.
The cause of ICP is unknown but genetic, hormonal, and environmental factors are likely involved . Environmental factors may also influence the expression of the disease.
Genetics — Genetic factors could explain familial cases and the higher incidence in some ethnic groups. The ABCB4 (adenosine triphosphate-binding cassette, subfamily B, member 4) gene encoding the multidrug resistance 3 (MDR3) protein (a canalicular phospholipid translocator) is primarily involved in a subtype of progressive familial intrahepatic cholestasis called PFIC3 . Heterozygous mutations in this gene have been found in a large consanguineous family in whom some women had episodes of cholestasis during pregnancy [8,9]. Several heterozygous mutations in the MDR 3 (ABCB4) gene were subsequently reported in patients with ICP [10-15]. The prevalence of such ABCB4 gene mutations in Caucasian patients suffering from ICP is 16 percent .
However, the genetic basis of ICP is complex, and some genes encoding for other canalicular transporters or their regulator may potentially be involved in its pathogenesis [17-19].