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Dr Gareth Nye is a lecturer of anatomy and physiology at Chester Medical School with research background in maternal and fetal health.

The nine months of pregnancy are the most crucial to life. Both the baby and the mother undergo extreme changes in both anatomy and physiology during and after the pregnancy. One of the most dramatic changes occur in the circulatory system (the blood vessels which allow blood to flow around the body).

Unfortunately, pregnancy and birth in humans is still somewhat of a mystery and that is leading to issues for mums. There are approximately 360,000 births every day worldwide, 750 of which end in a maternal death. That’s unfortunately around 30 per hour.

This death rate is significantly lower in developed countries such as ours, however one condition that occurs at high rates worldwide is preeclampsia. On World Pre-eclampsia Day, it’s a good time to spread awareness of this condition, especially in light of the current COVID-19 pandemic.

Pre-eclampsia Facts and Stats

  • Pre-eclampsia is characterised by high blood pressure and protein in the urine during pregnancy
  • It is seen in 6% of pregnancies in the UK
  • It is one of the leading causes of both mum and baby deaths worldwide
  • The only “cure” is delivery of the baby

What normally happens in pregnancy?

As little as nine days after fertilisation, the dividing and growing early fetus attaches to the wall of the uterus (termed the Endometrium). It then begins to burrow in to make a stable base to continue growing for nine months.

One of the main early aims is to find some of the blood vessels which run through the uterus. So cells from this fertilised embryo move through the uterus and invade. By day 12, these cells will have taken over the mums vessels (called spiral arteries) and begin to make them bigger (figure 1). This stage is important to allow for the large amount of blood flow needed later on in pregnancy which can reach up to 600ml every minute near the end of pregnancy.

Without this process of widening the mother’s uterine blood vessels, the baby will struggle to gain enough nutrients to grow properly and the mum’s blood pressure will increase (in other words – it takes more force to get something through a smaller tube then a bigger one, as the amount of fluid you are trying to push through gets bigger, the force required increases).

What happens in pre-eclampsia?

Pre-eclampsia has been described as a condition since Hippocrates first named it in the 5th-century BC, after the Greek word for lightning.

Despite this we currently don’t know the real cause but there are many possible theories behind the cause of pre-eclampsia. What we do know it that in cases of pre-eclampsia, the blood vessels in the mum’s uterus do not expand as they should (figure 1).

This causes the mum’s blood pressure to increase dramatically as blood tries to reach the baby.  This increase in blood pressure has knock on effects to other organs, like the kidneys, meaning they don’t work as they should. It also damages the blood vessels themselves, eventually causing them to break down entirely. Unfortunately, these combined often have a devastating effect on the growing baby.

It is diagnosed through observing both high blood pressure and protein in the mother’s urine, but most symptoms can be passed off as “normal pregnancy signs” such as swelling, headaches and heartburn, meaning patients are often seriously ill before a diagnosis can be made.

Why is it so dangerous?

Pre-eclampsia currently effects 6 in 100 pregnancies in the UK and is one of the leading causes of maternal and perinatal (the period immediately before and after birth) deaths worldwide. Symptoms can appear suddenly and the condition can get severe very quickly, and there is currently no test to predict a woman’s risk.

Although high blood pressure and protein in the urine are clear signs, in 10% of cases there is no protein present. This in combination with general symptoms that could be related to pregnancy mean making an early diagnosis is difficult.

Furthermore, when pre-eclampsia is diagnosed, there is no cure. The current “cure” is delivery of the baby. Of course the timing of the delivery has to weigh both the baby and mum’s needs and so most patients will be closely observed in hospital for as long as possible to ensure both have the best chance. 

Without good monitoring, pre-eclampsia can develop into the even more serious condition – eclampsia. Eclampsia is quite rare in the UK, with an estimated one case for every 4,000 pregnancies, and leads to severe fitting. 

How can we prevent serious outcomes?

There are a number of changes being put in place at maternity units due to the current COVID-19 pandemic. However this doesn’t mean pregnant women should avoid seeking help.

Women should always do the following to help monitor their pregnancies and reduce pre-eclampsia risk:

  • Talk to your midwives and doctors before or early in pregnancy about pre-eclampsia risk.
  • Attend all appointments. (If you are worried about attending the appointments, ring the team first to talk through your feelings. It is a scary time but you must still get checked out!)
  • Monitor blood pressure and weight regularly if you can, and contact your team immediately if either becomes unexpectedly high.
  • Do not rely on home Doppler machines or home monitoring kits, these are not reliable and can give false readings.
  • Know your family history, especially for pregnancy, high blood pressure and heart disease.
  • Eat a healthy diet and stay mentally well.

In essence, mums must trust their maternal instinct. If something doesn’t feel right, it’s always better to seek medical advice then wait.


World Pre-eclampsia Day
Figure 1 – Spiral artery remodelling (Roberts, 2014)

Roberts, J. M. (2014). Pathophysiology of ischemic placental disease. Semin Perinatol, 38(3), 139-145. Retrieved from doi:10.1053/j.semperi.2014.03.005

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