Intrahepatic cholestasis of pregnancy is a liver disorder that occurs in pregnant women. Cholestasis is a condition that impairs the release of a digestive fluid called bile from liver cells. As a result, bile builds up in the liver, impairing liver function. Because the problems with bile release occur within the liver (intrahepatic), the condition is described as intrahepatic cholestasis. Intrahepatic cholestasis of pregnancy usually becomes apparent in the third trimester of pregnancy. Bile flow returns to normal after delivery of the baby, and the signs and symptoms of the condition disappear. However, they can return during later pregnancies.

This condition causes severe itchiness (pruritus) in the expectant mother. The itchiness usually begins on the palms of the hands and the soles of the feet and then spreads to other parts of the body. Occasionally, affected women have yellowing of the skin and whites of the eyes (jaundice). Some studies have shown that women with intrahepatic cholestasis of pregnancy are more likely to develop gallstones sometime in their life than women who do not have the condition.

Intrahepatic cholestasis of pregnancy can cause problems for the unborn baby. This condition is associated with an increased risk of premature delivery and stillbirth. Additionally, some infants born to mothers with intrahepatic cholestasis of pregnancy have a slow heart rate and a lack of oxygen during delivery (fetal distress).

Genetic changes in the ABCB11 or the ABCB4 gene can increase a woman's likelihood of developing intrahepatic cholestasis of pregnancy.

The ABCB11 gene provides instructions for making a protein called the bile salt export pump (BSEP). This protein is found in the liver, and its main role is to move bile salts (a component of bile) out of liver cells, which is important for the normal release of bile. Changes in the ABCB11 gene associated with intrahepatic cholestasis of pregnancy reduce the amount or function of the BSEP protein, although enough function remains for sufficient bile secretion under most circumstances. Studies show that the hormones estrogen and progesterone (and products formed during their breakdown), which are elevated during pregnancy, further reduce the function of BSEP, resulting in impaired bile secretion and the features of intrahepatic cholestasis of pregnancy.

The ABCB4 gene provides instructions for making a protein that helps move certain fats called phospholipids across cell membranes and release them into bile. Phospholipids attach (bind) to bile acids (another component of bile). Large amounts of bile acids can be toxic when they are not bound to phospholipids. A mutation in one copy of the ABCB4 gene mildly reduces the production of ABCB4 protein. Under most circumstances, though, enough protein is available to move an adequate amount of phospholipids out of liver cells to bind to bile acids. Although the mechanism is unclear, the function of the remaining ABCB4 protein appears to be impaired during pregnancy, which may further reduce the movement of phospholipids into bile. The lack of phospholipids available to bind to bile acids leads to a buildup of toxic bile acids that can impair liver function, including the regulation of bile flow.

Most women with intrahepatic cholestasis of pregnancy do not have a genetic change in the ABCB11 or ABCB4 gene. Other genetic and environmental factors likely play a role in increasing susceptibility to this condition.

Normal Function

The ABCB11 gene provides instructions for making a protein called the bile salt export pump (BSEP), which is found in the liver. Bile salts are a component of bile, which is used to digest fats. Bile salts are produced by liver cells and then transported out of the cell by BSEP to make bile. The release of bile salts from liver cells is critical for the normal secretion of bile.

Health Conditions Related to Genetic Changes

Benign recurrent intrahepatic cholestasis

Mutations in the ABCB11 gene can cause benign recurrent intrahepatic cholestasis type 2 (BRIC2). People with BRIC2 have occasional episodes of impaired bile secretion that lead to severe itching (pruritus) and yellowing of the skin and whites of the eyes (jaundice). On occasion, people with BRIC2 have later been diagnosed with a more severe condition called progressive familial intrahepatic cholestasis type 2 (described below) when their symptoms worsened.

Affected individuals have a mutation in both copies of the ABCB11 gene. Mutations in the ABCB11 gene that cause BRIC2 lead to a 40 to 50 percent reduction of bile salt transport. The resulting buildup of bile salts in the liver leads to the signs and symptoms of BRIC2. It is unclear what causes the episodes to begin or end.

Progressive familial intrahepatic cholestasis

More than 100 mutations in the ABCB11 gene have been found to cause a severe form of liver disease called progressive familial intrahepatic cholestasis type 2 (PFIC2) that usually leads to liver failure. Development of this condition requires a mutation in both copies of the ABCB11 gene. Mutations in the ABCB11 gene that cause PFIC2 result in a 70 percent reduction to complete absence of bile salt transport out of the liver. The lack of transport causes bile salts to build up in liver cells, leading to liver disease and its associated signs and symptoms.

Mutations that lead to the production of a short, nonfunctional protein or cause no protein to be produced tend to be associated with severe liver disease that appears earlier in life. People with no functional BSEP protein also seem to be at a greater risk of developing a type of liver cancer called hepatocellular carcinoma.

Intrahepatic cholestasis of pregnancy

Women with a change in the ABCB11 gene are at risk of developing a condition called intrahepatic cholestasis of pregnancy. Affected women typically develop impaired bile secretion (cholestasis) and pruritus during the third trimester of pregnancy, and these features disappear after the baby is born. A common variation (polymorphism) in the ABCB11 gene is found more often in women who develop this condition than women who do not. This variation leads to a change in a single protein building block (amino acid) in the BSEP protein. Specifically, the amino acid valine is replaced by the amino acid alanine at position 444 of the protein (written as V444A). This change leads to a reduction in the amount of BSEP protein in liver cells. In rare cases, an uncommon change (a mutation) in one copy of the ABCB11 gene is found in women with intrahepatic cholestasis of pregnancy. A single mutation in this gene increases the risk of developing intrahepatic cholestasis of pregnancy. These mutations likely reduce the amount or function of the BSEP protein.

In women with either type of genetic change, enough BSEP function remains for sufficient bile secretion under most circumstances. Studies show that the hormones estrogen and progesterone (and products formed during their breakdown), which are elevated during pregnancy, further reduce the function of BSEP, resulting in impaired bile secretion and the signs and symptoms of intrahepatic cholestasis of pregnancy. Many factors, however, likely contribute to the risk of developing this complex disorder.

Other Names for This Gene

• ABC16
• ABCBB_HUMAN
• ATP-binding cassette, sub-family B (MDR/TAP), member 11
• bile salt export pump
• BRIC2
• BSEP
• PFIC-2
• PFIC2
• progressive familial intrahepatic cholestasis 2
• sister p-glycoprotein
• SPGP

Genomic Location

Normal Function

The ABCB4 gene (also known as MDR3) provides instructions for making a protein that helps move certain fats called phospholipids across the membranes of liver cells and release the phospholipids into a digestive fluid called bile. Outside the liver cells, phospholipids attach (bind) to bile acids, which are a component of bile that digest fats. Large amounts of bile acids are potentially harmful to cells; when they are bound to phospholipids, bile acids are less toxic.

Health Conditions Related to Genetic Changes

Progressive familial intrahepatic cholestasis

More than 45 mutations in the ABCB4 gene have been found to cause a severe form of liver disease called progressive familial intrahepatic cholestasis type 3 (PFIC3) that usually leads to liver failure. Affected individuals have a mutation in both copies of the ABCB4 gene. Mutations that lead to the production of a short, nonfunctional protein or cause no protein to be produced tend to be associated with more severe liver disease that appears earlier in life. ABCB4 gene mutations that cause PFIC3 impair the movement of phospholipids across cell membranes, leading to a lack of phospholipids available to bind to bile acids. A buildup of free bile acids damages liver cells, which causes the signs and symptoms of liver disease.

Intrahepatic cholestasis of pregnancy

Women with an ABCB4 gene mutation are at risk of developing a condition called intrahepatic cholestasis of pregnancy. Affected women typically develop impaired bile secretion and severe itching during the third trimester of pregnancy, and these features disappear after the baby is born. A single mutation in the ABCB4 gene leads to a mild reduction of the ABCB4 protein. Under most circumstances, though, enough protein is available to move an adequate amount of phospholipids out of liver cells to bind to bile acids. Although the mechanism is unclear, the function of the remaining ABCB4 protein appears to be impaired during pregnancy, which may further reduce the movement of phospholipids into bile. The lack of phospholipids available to bind to bile acids leads to a buildup of toxic bile acids that can impair liver function, including the regulation of bile flow. Problems with bile flow lead to the signs and symptoms of intrahepatic cholestasis of pregnancy. Many factors, however, likely contribute to the risk of developing this complex disorder.

Other disorders

Mutations in the ABCB4 gene are also associated with a rare condition called low phospholipid-associated cholelithiasis (LPAC). This condition is characterized by the formation of small pebble-like deposits of cholesterol in the gallbladder or bile ducts (gallstones). In LPAC, gallstones usually occur in people before age 40, which is young for the appearance of gallstones. In addition, affected individuals may have an accumulation of small crystals of cholesterol (microlithiasis) or a material called biliary sludge in the bile ducts of the liver. Biliary sludge is made up of solid particles that are usually dissolved in bile, including cholesterol crystals and calcium salts. The gallstones, cholesterol crystals, or biliary sludge can cause symptoms, such as pain, fever, nausea, or inflammation of the pancreas (pancreatitis), that can recur even after removal of the gall bladder.

It is thought that mutations in the ABCB4 gene that are involved in LPAC impair the protein's ability to transfer phospholipids into bile. Because phospholipids help keep cholesterol dissolved in bile, the lack of phospholipids can result in the formation of gallstones or crystals from undissolved cholesterol.

Other Names for This Gene

• ATP-binding cassette, sub-family B (MDR/TAP), member 4
• ATP-binding cassette, subfamily B, member 4
• MDR3
• MDR3_HUMAN
• multidrug resistance protein 3
• multiple drug resistance 3
• P glycoprotein 3/multiple drug resistance 3
• P-glycoprotein-3/multiple drug resistance-3
• PFIC-3
• PGY3

Genomic Location

Susceptibility to intrahepatic cholestasis of pregnancy is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to increase the risk of developing the disorder. Some women with an altered gene do not develop intrahepatic cholestasis of pregnancy. Many other factors likely contribute to the risk of developing this complex disorder.

Intrahepatic cholestasis of pregnancy (ICP) is suspected during pregnancy when symptoms of itching (pruritis) present after 25 weeks of gestation with absence of a rash or underlying maternal liver disease. The diagnosis is typically confirmed with the finding of elevated serum bile acids.

In the presence of a family history of intrahepatic cholestasis of pregnancy (ICP) and/or known mutations in either the ABCB11 or ABCB4 genes, genetic testing is available.

Treatment for intrahepatic cholestasis of pregnancy aims to relieve itching and prevent complications. Medications utilized to relieve itching might include ursodiol (Actigall, Urso), which helps decrease the level of bile in the mother's bloodstream, relieves itchiness and may reduce complications for the baby. To prevent pregnancy complications, close monitoring of the baby might be recommended. Even if prenatal tests appear normal, induction of early labor might be recommended.

Intrahepatic cholestasis of pregnancy is estimated to affect 1 percent of women of Northern European ancestry. The condition is more common in certain populations, such as women of Araucanian Indian ancestry in Chile or women of Scandinavian ancestry. This condition is found less frequently in other populations.