Research into pre-eclampsia

Something as simple as salt could help prevent a life-threatening condition which affects pregnant women and their unborn babies. Dr Hiten Mistry explains the latest research to Sarah Brealey.

hiten mistry

Dr Hiten Mistry in the lab

Pre-eclampsia is a potentially serious condition which affects up to 6 per cent of pregnancies. Thought to be caused by a problem with the placenta, the signs are high blood pressure and the presence of protein in the urine on testing. In serious cases, it can be life-threatening to mother and baby, or cause premature births. Even mild cases raise the risk of developing heart disease for both mother and baby later in life. The only cure is for the baby and placenta (afterbirth) to be delivered.

Dr Hiten Mistry, BHF Intermediate Research Fellow and his group at the University of Nottingham, are looking at whether salt intake early in pregnancy could help the placenta work more effectively, to prevent pre-eclampsia. 

Pre-eclampsia is a potentially serious condition which affects up to 6 per cent of pregnancies.

He says: “The disease starts fairly early in pregnancy, before 20 weeks gestation when the placenta or afterbirth is attaching to the mother’s womb. But the symptoms don’t arise and it can’t be diagnosed until later on - usually 30 weeks onwards. At present the only cure for pre-eclampsia is delivery of the baby and more importantly the placenta.”

He is investigating whether consuming more salt early in pregnancy could prevent the condition.

He says: “We are turning thinking on its head. Outside pregnancy, salt causes an increase in blood pressure, but early in pregnancy more salt may actually help to lower it.

“We are not saying at the moment that pregnant women need to eat more salt. We need to be very careful, and check the effects of salt on the baby too. Getting the level right is really important.”

The hormone aldosterone is involved in maintaining fluid balance in the body, by increasing the amount of sodium the body sends into the bloodstream or the amount of potassium released in the urine. It can also cause the bloodstream to re-absorb water with the sodium to increase blood volume. All of this is important to the control of blood pressure. 

Magnified image of part of the placenta early in pregnancy, illustrating the branching of cells that attach to the womb lining

Magnified image of part of the placenta early in pregnancy, illustrating the branching of cells that attach to the womb lining

In pregnancy, this hormone regulates fluid balance in the unborn baby as well as the mother. Dr Mistry says: “Aldosterone is needed at a certain rate to allow the placenta to grow. But in pre-eclampsia, mother and baby have less of it. Salt can be a replacement for that, it allows fluid to be re-absorbed into the bloodstream and for blood volume to increase. We think salt can also possibly have a beneficial effect in the way the placenta implants into the womb.”

In a four-year BHF-funded project, the team is looking at salt intake in women with and without pre-eclampsia, and whether sensitivity to salt changes in pregnancy. They will also look at how salt intake affects the placenta itself. If this goes well they will run a clinical trial to test the effects of consuming more salt in pregnancy. It could mean that in six or seven years, we have better guidance to give to pregnant women about how to reduce their risk of pre-eclampsia. 

Serious condition

Pre-eclampsia is the second highest cause of maternity-related deaths in the UK. It can cause stillbirth too – it is estimated that around 1,000 babies die each year because of pre-eclampsia.

But the health risks are also longer-term health risks for both mother and baby. This is partly because pre-eclampsia makes it more likely the baby will be born early. 

A mother with pre-eclampsia has an eight times higher risk of developing cardiovascular disease than she otherwise would. For the baby the risk is five times higher.

Dr Mistry says: “Premature babies are at high risk of a range of metabolic diseases, such as cardiovascular disease and diabetes. This is because the first few weeks of life, premature babies lay down fat in the abdomen and around the blood vessels where it gives them a pre-disposition to high blood pressure. On top of that, in pre-eclampsia the baby is already used to an environment of high blood pressure, which makes it even more likely they will have high blood pressure.”

BHF funding

We’ve funded Dr Mistry with a four year Intermediate Research fellowship worth £478,876 to carry out this work. He says: “BHF funding is essential to my work. The BHF is aware that this is a big problem which affects mothers and babies.”

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