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Your
questions answered
What is pre-eclampsia?
How common is it - and how dangerous?
Who is most at risk?
What causes pre-eclampsia?
What happens to the mother?
What are the symptoms?
Is there a cure?
What treatments are used?
What happens to the baby?
Are there any long term effects?
What happens in the next pregnancy?
Can pre-eclampsia be prevented?
What can be done to reduce the risk of recurrence?
What is pre-eclampsia?
Pre-eclampsia is an illness arising only in pregnancy which
can affect the mother, her unborn child, or most commonly,
both. It can occur at any time from around twenty weeks
to as late as several days after delivery. In the mother,
the condition causes a number of symptomless disturbances
– including raised blood pressure (hypertension) and
leakage of protein in the urine (proteinuria) – which
can progress to serious illness if undetected. The unborn
baby may grow more slowly than normal or suffer potentially
dangerous oxygen deficiency.
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How common is it – and how
dangerous?
In its broadest form and including gestational
hypertension, pre-eclampsia affects as many as one in 10
of all pregnancies, making it the most common of the serious
antenatal complications. It occurs more often in first pregnancies,
although a minority of women who have suffered it once get
it again in one or more subsequent pregnancies. Pre-eclampsia
is usually mild, but one in every 100 first pregnancies
is so severely affected that there is a serious risk to
the life of the baby – and even the mother. Every
year in the UK about 500-600 babies die because of pre-eclampsia
– many of these as a consequence of premature delivery
rather than the disease itself. Some six mothers die each
year from complications of pre-eclampsia in the UK.
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Who is most at risk?
No one can predict with certainty who will get pre-eclampsia.
Every woman is at risk in her first pregnancy, although
the risk is greater for those with a strong family history
of the complication. Women who have had pre-eclampsia in
a first pregnancy may get it again. However, those who have
enjoyed normal first pregnancies rarely get pre-eclampsia
in subsequent pregnancies. The risk of repeat attacks is
increased if the mother is carrying twins or has one of
several chronic medical problems, including high blood pressure,
kidney disease, diabetes or, to a lesser extent, migraine.
Older mothers (particularly the over 35s), younger mothers
(those under 20) and those of a short stature may also be
at risk. Women with a body mass index over 30 may also be
of higher risk. More on risk factors.
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What causes pre-eclampsia?
No one knows for sure, although genetic factors are probably
involved, since women whose mothers and sisters have suffered
pre-eclampsia are more likely to get it themselves. What
is known is that pre-eclampsia originates in the placenta
– the special pregnancy organ which links a mother
to her unborn child. The placenta needs a large and efficient
blood supply from the mother to sustain the growing baby.
In pre-eclampsia, the placenta runs short of blood either
because its demands are unusually high – as with twins
– or because the arteries in the womb did not enlarge
as they should have done when the placenta was being formed
in the first half of pregnancy. This shortage of blood has
potentially serious consequences for mother and baby.
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What happens to the mother?
Signals from the deficient placenta affect the
mother's blood vessels, raising her blood pressure and disturbing
her kidney function, so that waste products which should
be excreted in the urine accumulate in the blood, while
valuable blood proteins leak into the urine. As the disease
progresses, the mother's liver, lungs, brain and blood clotting
system can also be affected. Eclampsia (convulsions), cerebral
haemorrhage (stroke), pulmonary oedema (fluid in the lungs),
kidney failure, liver damage, and breakdown of the blood
clotting system (disseminated intravascular coagulation)
are the most dangerous complications – all of them
fortunately, very rare.
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What are the symptoms?
Pre-eclampsia has no symptoms in its early stages, when
it can be detected only in routine screening tests carried
out in antenatal clinics. A combination of rising blood
pressure and protein in the urine suggests pre-eclampsia,
although there is no foolproof diagnostic test. Swelling
(oedema) of the hands, feet and face caused by fluid retention
is often a feature of pre-eclampsia, but is also common
in normal pregnancy. Symptoms like upper abdominal pain,
vomiting, severe headache, and visual disturbances (such
as 'flashing lights') sometimes arise when the disease has
reached an advanced stage. These symptoms should therefore
never be ignored in pregnancy although, since each can have
other causes, they do not necessarily signal danger.
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Is there a cure?
A pregnancy complicated by pre-eclampsia cannot
be restored to normal. But the disease itself is ended by
the delivery of the baby and with it the placenta which
is the seat of the problem. This is usually in the best
interests of both mother and baby. But dilemmas arise when
early delivery would solve the mother's problems but put
the baby at risk of the effects of extreme prematurity.
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What treatments are used?
Mothers are normally admitted to hospital if they
have severe pre-eclampsia – which means protein in
the urine as well as high blood pressure. This is to enable
doctors and midwives to monitor the progress of mother and
baby as closely as possible so that delivery can be carried
out before complications set in. Pre-eclampsia is progressive
– it doesn't get better and usually gets worse. So,
once admitted, mothers are not normally allowed home until
after delivery. Antihypertensive drugs, which reduce high
blood pressure, are often prescribed; although they do not
affect the underlying disease, they can reduce the risk
of some complications, such as cerebral haemorrhage. Anticonvulsant
drugs may also be prescribed to ward off eclamptic fits.
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What happens to the baby?
As the blood supply from the mother to the placenta
is restricted, the baby's supply of nutrients and oxygen
may be reduced, leading at first to slower than normal growth
(intrauterine growth retardation – IUGR) and later
to oxygen starvation. Once pre-eclampsia is suspected or
known, the unborn baby is monitored as closely as the mother
so that the delivery can be carried out before its problems
become serious. Decisions about delivery are particularly
difficult when a premature foetus (of under 28-30 weeks'
gestation) is severely affected by pre-eclampsia but could
not be certain of survival outside the womb.
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Are there any long term effects?
For the great majority of mothers, delivery reverses all
the effects of pre-eclampsia, although recovery may be preceded
by a final crisis. For an unfortunate few, however, some
organ damage remains after the disease itself is cured.
It is not uncommon for women who have suffered pre-eclampsia
in one or more pregnancies to develop chronic high blood
pressure later on in life. But this is thought to reflect
an inbuilt tendency to blood pressure problems rather than
a history of pre-eclampsia. There are no known health problems
for babies and children who have been affected by pre-eclampsia
unless they suffered extreme starvation of oxygen in the
womb or had to be delivered very prematurely.
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What happens in the next pregnancy?
Women who have suffered pre-eclampsia in a first pregnancy
should be monitored more closely and more frequently than
usual in subsequent pregnancies, since there is a risk that
the condition will recur, although usually in a milder form.
Nevertheless, most mothers who have suffered even the most
severe form of the disease in a first pregnancy enjoy perfectly
normal subsequent pregnancies.
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Can pre-eclampsia be prevented?
There is no hard evidence that pre-eclampsia can
be prevented by what you eat, whether you smoke or drink,
how hard you work or how much rest you take. However, there
is some evidence that small daily doses of aspirin, taken
under medical supervision, may be able to prevent or delay
the onset of the disease in some high-risk mothers. This
is because aspirin works directly on specialised blood cells
known as platelets, which help with clotting and are involved
in the disease process.
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What can be done to reduce the
risk of recurrence?
Your best plan is to co-operate fully with the system of
antenatal checks, which is designed to detect the earliest
signs of pre-eclampsia. If possible, have yourself referred
to a consultant who takes a special interest in pre-eclampsia,
and see him or her early in your pregnancy – or even
before conception – to plan your antenatal care programme.
Take
an active interest in your antenatal checks; never miss
an appointment; make sure you are monitored more frequently
if your blood pressure is raised, and admitted to hospital
if protein appears in your urine (only one or more 'plusses'
(+) in a urine test is important: 'trace amounts' can be
ignored.) Always report any worrying signs or symptoms to
your doctor and do not allow him or her to dismiss you without
first checking your blood pressure and urine.
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