Pre-Eclampsia Explained

Published on: June 07, 2018

The Bumps Team will be sharing a series of articles examining common complications and conditions of pregnancy and postpartum and their implications for mums and babies. This month, midwife and BAMBI Bumps and Babies Co-ordinator, Emma McNerlin looks at Pre-Eclampsia.

By Emma McNerlin

What is Pre-eclampsia?

Affecting 2-7% [1] of all pregnancies, pre-eclampsia or pre-eclamptic toxaemia (PET) is a condition diagnosed by the presence of hypertension (high blood pressure) and proteinuria (protein in the urine) and associated with serious risks for both mother and baby – so early detection and treatment is vital.

What causes it?

In a healthy pregnancy changes in the body mean that blood pressure drops slightly during the second trimester, as blood vessels dilate to accommodate extra blood made to sustain the pregnancy. Blood pressure then rises again during the third trimester.

Pre-eclampsia, however, impairs dilation. The walls of the blood vessels in the placenta consequently secrete biochemical substances causing protein to leak into the maternal bloodstream. It’s not fully understood why. [2]

What are the symptoms and how is it diagnosed?

Pre-eclampsia is often symptomless, until the blood pressure and protein levels in the blood and urine reach dangerous levels, leading to severe PET.

A blood pressure reading of over 140/90, or an increase of +30 systolic (top number) and +15 diastolic (bottom number), with the presence of more than trace amounts of protein in the urine indicate pre-eclampsia. Severe pre-eclampsia shows a reading of >160/110.

Thankfully severe PET affects just 0.5% of pregnancies but remains a life-threatening multi-organ condition, and if left untreated can lead to serious damage to the kidneys, liver, and blood clotting. It can also develop to eclampsia, or convulsions, and increased risk of brain bleeds, and stroke.

Symptoms typically present themselves in the late second and in the third trimester and can include severe frontal headache, visual disturbance including flashing lights or blurred vision, abdominal pain, especially under the ribs on the right, nausea and vomiting, dulled reflexes and sudden and serious swelling of the face and hands.

In more severe cases, it can present around the 20th week of pregnancy or even postnatally (44% of cases [3]), so even after delivery close monitoring should continue until blood pressure and symptoms subside.

The gold standard test for diagnosis measures the total amount of protein in a 24-hour urine collection and regular blood tests track kidney and liver function.

Can it harm the baby?

Yes, pre-eclampsia can adversely affect placental function. Baby’s growth is monitored closely by regular ultrasound scan, which also measures the efficiency of oxygen and nutrient transfer through the umbilical cord and measures the amount of amniotic fluid. The main risk of PET to the baby is restricted growth and hypoxia or lack of oxygen. Hypoxia can lead to seizures and brain damage or cerebral palsy in babies. It is vital the mums monitor the pattern of baby’s movements NOT count an arbitrary number of kicks. Any reduction in the normal pattern of movement should be reported to your doctor immediately. In cases of severe PET, it may become necessary to deliver the baby before term; in this case, the mother would also receive a course of steroids by injection to help to mature the baby’s lungs. (NICE, 2010)

How is it treated?

Screening and early diagnosis of PET are vital for improving outcomes for mum and baby and a recent study of over 30,000 pregnancies in six countries suggests aspirin can cut the risk of early pre-eclampsia by 82% and pre-term pre-eclampsia by 62%. [4] So those identified as being at increased risk of developing PET may be prescribed aspirin from 12 weeks until birth.

High blood pressure can also be treated with medication to attempt to stop the progression towards severe pre-eclampsia and eclampsia, though this does not treat the cause.

In cases of severe or rapidly progressing pre-eclampsia, the mother may receive a controlled IV infusion of Magnesium Sulphate, to help prevent eclamptic convulsions, though this can only be administered if birth is planned within 24 hours.

Generally, your doctor will try to manage the symptoms with medication and close observation in the hospital to prolong the pregnancy for as long as it is safe for mum and baby.

Ultimately, the only effective treatment is delivery of the baby – balancing and mitigating as much as possible, the risks to the mother’s health and the risk of hypoxia to the baby by continuing the pregnancy.

What are the implications for birth and care?

Whilst PET has serious implications for both mum and baby, and safety is of paramount importance to both parents and the medical team, it is also important that the care plan, clinical results, and implications of any medication are fully explained by the doctor.

A diagnosis of PET can be a worrying time for expecting parents, so patient and compassionate care is essential. As a high-risk condition of pregnancy, close monitoring is required, and open communication helps parents to understand that the plan for birth may also be adjusted.

Depending on the circumstances, induction of labour may be favoured over planned C-section, but this will depend both on the doctor and on the clinical details of each individual case.

Thanks to highly developed screening and diagnosis protocols, serious adverse outcomes are usually avoided.

The information provided in this article is for informational purposes only and is not intended to substitute or replace medical advice. If you have any concerns about the health of you or your baby, please contact your doctor.


[1] Robson, S. and Waugh, J. eds (2013) Medical Disorders of Pregnancy: Wiley Blackwell P

[2] Fraser, D. and Cooper, M. (2016) Myles Textbook for Midwives

[3] Winter, C. et al (2012) Practical Obstetric Multi-Professional Training: Cambridge Medical Press

[4] ASPRE Study, 2017

Further Reading

APEC Action on Pre-Eclampsia Precog guideline accessed online available at:

National Institute of Health and Clinical Guidance (NICE) 2010: Guideline on Pre-Eclampsia. Available online Accessed at:

Rolnik et al (2017) ASPRE trial: performance of screening for preterm pre-eclampsia. Accessed online available at:

About the Author

Emma McNerlin is a UK trained and registered Midwife, First Aid Instructor and owner of Bumpsy Daisy Café and Community; a cafe and parenting community centre for new and expecting parents offering birthing classes, hypnobirthing, First Aid workshops and baby classes.

The views expressed in the articles in this magazine are not necessarily those of BAMBI committee members and we assume no responsibility for them or their effects. BAMBI welcomes volunteer contributors to our magazine. Please contact