41. Obstetric Cholestasis. (OC)
|a.||what variety of chicken is this?||Araucanian|
|b.||what colour are its eggs?||Blue|
|c.||what on earth has it to do with obstetric cholestasis?||See below|
|d.||what has it to do with the word "poncho"?||See below|
|e.||in Europe, OC is most common in Scandinavia.||True|
|f.||OC in the UK is most common in women of Indian and Pakistani extraction.||True|
OC usually presents with jaundice.
|h.||current management of OC entails delivery before 38 weeks.||See below|
|i.||OC carries an increased risk of PPH.||See below|
|j.||ursodeoxycholic acid is recommended to reduce fetal risk.||False|
|k.||dexamethasone is recommended to reduce fetal and maternal risk.||False|
|l.||the risk of recurrence in a subsequent pregnancy is ~ 90%||True|
|m.||the risk of OC for a woman with an affected sister is ~ 20%||True|
|n.||the symptoms of OC can recur if an affected woman takes the Pill||True|
I keep chickens and the picture is of my Araucanian.
It is a rather scruffy, silver-grey bird, with masses of feathers about its head which obscure its features.
It lays large blue eggs, despite being a small bird, and puts on the most astounding song and dance every time it does.
This does not surprise me, given the relative size of its eggs.
A bit like the average woman delivering a 20 lb. baby.
I doubt Araucanian chickens will ever appear in the College MRCOG or DRCOG MCQ databases.
But I was convinced that you would want to know of my little marvel.
The link with OC is that the chickens are named after the Araucanian Indians from Chile.
Araucanian women have the world's highest incidence of OC.
The RCOG guideline says the incidence in the Araucanians is 5%.
Other sources put it as high as 28%!
The Araucanian language gave us the word "poncho".
I just add this gem as I am sure that the etymology of the word has long intrigued you.
You'll be in a position, the next time you see someone in a poncho, to make pleasant conversation about:
the origins of the word poncho,
the colour of the Araucanian chicken's eggs,
the link with OC & pruritus etc.
You will be a conversational superstar.
But be careful not to link their poncho with pruritus.
They may think you are getting a bit snide about their hygiene.
Key facts to remember:
No agreed definition:
pruritus + abnormal LFTs that resolve in the puerperium.
Other causes of pruritus & abnormal LFTs must have been excluded.
Elevated bile acids widely used in the UK, but not mandatory for the diagnosis.
Causes intense pruritus, often of palms and soles.
Possibly causes late gestation fetal death in utero.
No means of identifying the "at-risk baby".
No means of monitoring to give reassurance on fetal welfare.
Causes premature delivery.
No proven, effective treatment; either drugs or early delivery.
Possible increase in prothrombin time and risk of postpartum haemorrhage.
The College says there is no evidence to support early delivery.
College advises it is "reasonable" to prescribe vitamin K, 10 mg. daily, from time of diagnosis.
Ursodeoxycholic acid and dexamethasone possibly beneficial, but insufficient research to support their routine use.
Wide geographic variation, commonest in Chile, Scandinavia and SE Asia.
Probably an oestrogen effect: incidence highest in 3rd. trimester,
oestrogen levels peak in 3rd trimester,
risk of recurrence on oestrogen-containing contraception.
High risk of recurrence in pregnancy for the sufferer.
Significant risk of OC for her sisters.
The following fills out the detail.
It may help the essential facts to adhere to your grey matter.
In the UK the incidence of OC is ~ 0.7% in Caucasians, but double that in women of South Asian origin.
In Europe it is most common in Scandinavia.
When I was a junior doctor, OC was regarded as an interesting phenomenon but innocuous.
In the 1980s adverse fetal outcomes, particularly fetal death in utero (FDIU) in the last two or three weeks, were described.
OC started to be managed very aggressively.
The risk of FDIU led to the almost universal practice of elective delivery before 38 weeks.
The College put a spanner in the works in 2006 in a “green top” guideline.
This concluded that nowadays the risk of stillbirth for pregnancies with OC is no greater than for non-OC pregnancies.
It reached this conclusion by looking at data from later papers rather than those published in the 1970s.
It acknowledged that the earlier papers might have included a higher proportion of severe cases.
As time goes by we tend to get better at diagnosing uncommon conditions.
If you dilute the OC population in a trial with loads of very minor cases, you may mask a small but real risk that is proportional to the severity of the illness.
The guideline also concluded that the effects of early delivery are unclear.
Does all of this mean that OC does not carry an increased risk of FDIU and that we can stop fishing babies out at 38 weeks?
The guideline asked if women with OC should be offered early delivery.
It advised that there was insufficient evidence to support or denigrate this practice!
It further advised that “the timing and risks of delivery should be discussed on an individual basis”.
So thanks a lot RCOG- that's really helpful!
It reported the figures for 1500 OC pregnancies.
There were 18 stillbirths.
13 occurred before 37 weeks and 5 between 37 and 38 weeks.
Most of the babies were delivered early, so we can’t know how many stillbirths were prevented.
The risks of early delivery include breathing problems for the baby and, possibly, increased Caesarean section rates for the mum.
One would expect a policy of early delivery to put up Caesarean section rates.
But the College guideline says the evidence is inconclusive.
As you can imagine, the guideline has caused great confusion.
I suspect that most people will continue with early delivery.
They'll wait until there is evidence from a trial comparing early delivery with non-intervention.
This should quantify the risk of FDIU and balance of the risks and benefits of early delivery.
For the exam, you need to say that:
OC may carry an increased risk of FDIU,
there is no effective means of identifying the at-risk baby,
there is no proven method of monitoring fetal welfare,
there is no proven, effective, safe drug treatment,
and that we don’t know if early delivery works.
OC does not have a universally agreed definition.
It is obviously a pregnancy condition with pruritus, for which there is no other explanation.
It usually presents in the third trimester.
The pruritus classically affects the soles and palms, though it can be generalised.
It can be severe.
There is no rash, unless one inflicted by scratching.
If there is a rash, a dermatological opinion makes sense, as few obstetricians would see themselves as smart at dermatological diagnosis.
The differential diagnosis includes skin conditions like prurigo and eczema through to scabies.
The diagnosis involves abnormal liver function tests (LFTs), but there are many that are used to confirm the diagnosis and none that is a “must”.
The pruritus and abnormal LFTs must clear in the puerperium.
LFTs may show elevated results in the first week or so of the normal puerperium, so the tests must be done later than this.
Liver disease has to be looked into: hepatitis A, B and C, Epstein Barr or cytomegalovirus infection, gallstones, cholecystitis, autoimmune liver disease, acute fatty liver of pregnancy etc.
Hepatitis C virus (HCV) increases the risk of OC. (See MCQ5, question 45.)
Hepatitis C is a treatable condition, so it makes sense to screen for it.
You might expect OC to causes jaundice, pale stools and dark urine, but these are uncommon.
Liver function tests and an ultrasound scan help.
Alkaline phosphatase is usually elevated in normal pregnancy - it is made by the placenta - so not a lot of help.
Transaminases are raised in OC.
Pregnancy-specific values must be used.
Pruritus accompanied by raised transaminases is likely to be OC.
Most UK hospitals see measurement of bile acids as a diagnostic sine qua non.
Some authorities accept elevated gammaGT and bilirubin to make the diagnosis.
The College advises that weekly LFTs from the time of diagnosis is "reasonable".
It gives no clue as to why they should be done so often.
What are you supposed to be looking for?
A scan may show gallstones.
In one study of OC, 13% had gallstones.
It is thought that at least one abnormal gene predisposes to both gallstones and OC.
It is not thought that gallstones cause OC or vice versa.
As noted above, there may be an increased risk of FDIU.
There is no method of fetal welfare monitoring that can guarantee to prevent it.
There is no fully evaluated, effective and safe drug treatment.
As a result, the main element of the management has been early delivery to pre-empt FDIU.
There are various theories about the causation of fetal death.
One on the most attractive, with some laboratory support, is that bile acids depress the contractility of fetal heart muscle cells and cause cardiac arrest.
There is an increased risk of spontaneous premature delivery.
There is an increased incidence of meconium-stained liquor in some, but not all, reports.
The prothrombin time can be prolonged and has been associated with an increased risk of postpartum haemorrhage.
This has been attributed to reduced absorption of fats and fat-soluble vitamins, like vitamin k, from the bowel.
It has also been attributed to the underlying hepatic dysfunction.
James' "High Risk Pregnancy" recommends vitamin K, 10 mg. orally, on a daily basis from the time of diagnosis.
However, the College guideline says that the evidence of increased incidence of PPH is unclear.
Nonetheless, the College states that it is "reasonable" to give vitamin K as there is a good theoretical basis for doing so.
The administered vitamin K has to be water-soluble, for obvious reasons.
The two main treatments that have been tried are ursodeoxycholic acid (UDCA) and dexamethasone.
There is conflicting evidence about their effect on pruritus.
We don't know if they improve the fetal outcome.
There are no reports of long-term follow-up of babies who got UDCA in the womb.
Dexamethasone to treat OC has usually been given for > 1 week.
Short courses of steroids, e.g. for lung maturation, are thought safe.
There is some evidence linking longer courses with IUGR and abnormal brain development.
This is obviously a concern re the use of steroids in OC.
More research is needed, so neither drug is routine.
The College advice is essentially that the drugs should only be used in proper clinical trials.
If they are used outside clinical trials, the woman must be counselled about the lack of data on efficacy and safety.
OC is almost certain to recur in future pregnancies (~90% risk) and runs in families.
If your sister had OC, you run a risk of ~20%.
Women who have OC may produce a similar condition on oestrogen-containing oral contraceptives.
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