What is pre-eclampsia?

02 April 2019

Interview with

Catherine Aiken, Cambridge University and Addenbrooke's Hospital

PREGNANCY

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Many women have healthy, uncomplicated pregnancies. But this isn’t the case for everyone. Around 7 or 8% develop a condition called pre-eclampsia. This can be potentially very serious, and women who develop it will usually be monitored closely throughout their pregnancy. Catherine Aiken is an obstetrician and researcher at the University of Cambridge, and she spoke with Katie Haylor. Firstly, Katie asked, what exactly is pre-eclampsia, and how would women know they had it?

Catherine - So pre-eclampsia is a complication of pregnancy that's characterised mainly by the mother's blood pressure going up, and protein beginning to appear in her urine later on in the pregnancy, but it's not limited to that. Pre-eclampsia can affect all parts of the mother’s organ systems. It can affect her kidneys, her liver, it can affect her brain, and it can also affect the growth of her developing baby at the same time. And so many women present with initial symptoms; for example headaches, flashing lights in their vision, they might notice swelling.

And one of the difficulties with pre-eclampsia is really the enormous range of things that different women experience when they actually develop the disease, and that's why we spend so much time monitoring the blood pressure of women in the third trimester. It's why we dip the urine during antenatal visits, because we know that this problem is common. We know if we can pick it up mums and babies will do a lot better, but it can mimic so many things and that's why we spend so much time trying to identify who has actually got it and who is at risk.

Katie - You mentioned the third trimester there, is that when people tend to get it?

Catherine - It's when people tend to get it. We do see women who develop this very severe form of it earlier than that, but most mums will find it developing later on as the pregnancy progresses.

Katie - How much do we know about why it happens in the first place? You mention some symptoms, but do we know what it's caused by?

Catherine - What we know is that it's not primarily a disease of the mother or the baby but it seems to arise from the placenta. And the placenta is one of those really fascinating organs that seems to be the answer to quite a lot of those really major complications that we see in pregnancy.

And it seems that pre-eclampsia arises from the very very early growth of the placenta and so interestingly this condition arises way way before we see it, which is late in the pregnancy, at the time when the placenta's trying to plug in to the mum’s circulation in order to feed the baby and support its growth. And it seems to be in that initial phase that actually the vessels don't develop properly and that's when pre-eclampsia has its beginning, although we don't see the effects until much later on.

Katie - How can it be treated then, or managed? What do you with a lady who has it?

Catherine - Well, ultimately the only thing that will end pre-eclampsia is delivering the placenta; that course means delivering the baby. So often we're in a situation where it's too early for the baby to be born. We don't want to give the baby the problems of prematurity but we know that both mum and baby are at risk from pre-eclampsia, and then we've got a difficult balance between can we continue with this pregnancy where the mother is at risk from these complications? Versus do we deliver a baby that then will face the problems of prematurity. And so a lot of our management is making these really tough judgement calls about when the right time to deliver is, and in the meantime trying to control the symptoms in the mother, trying to control the high blood pressure, make sure that we keep her safe from all the things women can experience during this complication.

Chris - Now I happened to be reading what's been published this week Catherine, there's a very interesting paper with your name on it actually! We've talked very much about the mother's health here, but what about the unborn foetus if we don't treat or we don't manage pre-eclampsia properly? What are the consequences for the baby?

Catherine - Well, we know quite a lot about the immediate complications for the baby. We know that there at risk of being born small and we know that they're at risk of being born early and both of those things carry a lot of risk with them.

What we've been looking at is what happens later in life and that's the bit that we really don't have enough knowledge about at the moment, which is are those babies if we get them through the initial phase, do they catch up to their development, continue normally and so on?

We've been looking at fertility in the female babies of women with pre-eclampsia, and what we find in our animal model is they have actually got a lower egg reserve in their own adult life, and so their fertility may be impaired by this womb environment that they've been developing in.

Chris - So a baby born to a lady who's had pre-eclampsia will ultimately have fewer eggs in her ovary, when she comes to have her own children, she may therefore suffer a shorter reproductive life?

Catherine - Absolutely. That's what our works and the models that we've been looking at indicates, and that's really fascinating to us because we know that pre-eclampsia has all of these problems arise immediately, but we are only really beginning to see glimpses into the future of what it means in the longer term.

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