What causes obstetric cholestasis?
Obstetric cholestasis is a problem that can occur with the way the liver works during pregnancy. To understand what obstetric cholestasis is, you first need to understand a little bit about how the liver works normally.
The liver is in your tummy (abdomen), on the upper right-hand side. The liver has many jobs. These include:
- Storing fuel for the body.
- Helping to process fats and proteins from digested food.
- Making proteins that are needed for blood to clot properly.
- Processing some medicines which you may take.
- Helping to remove toxins from the body.
The liver also makes bile. Bile helps to break down (digest) fats in the gut. Bile is a greenish-yellow fluid which contains bile acids, bile pigments and waste products such as bilirubin. Liver cells pass bile into bile ducts inside the liver. The bile flows down these ducts into larger and larger ducts, eventually leading to the common bile duct. The gallbladder is like a cul-de-sac reservoir of bile which comes off the common bile duct. After you eat, the gallbladder squeezes bile back into the common bile duct and down into the upper part of the gut (duodenum).
Exactly why obstetric cholestasis happens is not clear. Hormonal and genetic factors may be responsible:
- Hormonal factors. Pregnancy causes an increase in oestrogen and progesterone hormones. These can affect the liver in a way which slows down the bile as it passes out along the tiny bile ducts. Some pregnant women may be more sensitive to these hormonal effects.
- Genetic factors. Obstetric cholestasis seems to run in some families (although it may skip some generations). One theory is that women who develop obstetric cholestasis may have inherited a very slight problem with the way bile is made and passes down the bile ducts. This doesn't matter when they aren't pregnant but the high level of hormones made during pregnancy may tip the balance to really slow down the flow of bile.
There may be other environmental factors which play a part. However, whatever the underlying cause, it is pregnancy that triggers the problem. Within a week or so after giving birth the itch stops and there is no long-term problem with the liver.
Further reading and references
Obstetric Cholestasis; Royal College of Obstetricians and Gynaecologists (May 2011)
Gurung V, Middleton P, Milan SJ, et al; Interventions for treating cholestasis in pregnancy. Cochrane Database Syst Rev. 2013 Jun 246:CD000493. doi: 10.1002/14651858.CD000493.pub2.
Lee NM, Brady CW; Liver disease in pregnancy. World J Gastroenterol. 2009 Feb 2815(8):897-906.
Williamson C, Geenes V; Intrahepatic cholestasis of pregnancy. Obstet Gynecol. 2014 Jul124(1):120-33. doi: 10.1097/AOG.0000000000000346.
Kong X, Kong Y, Zhang F, et al; Evaluating the effectiveness and safety of ursodeoxycholic acid in treatment of intrahepatic cholestasis of pregnancy: A meta-analysis (a prisma-compliant study). Medicine (Baltimore). 2016 Oct95(40):e4949.
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