Fetal complications of preeclampsia

When early onset disease occurs delivery is often required for maternal and/or fetal reasons this adds the burden of prematurity to these babies and they are more likely to die or have short and long term morbidity.

These are the same principles as for other antenatal risk assessments that we have looked at in week 1.

• Prediction
• Prevention
• Early detection
• Surveillance
• Treatment
• Delivery

A large international study called SCOPE (Screening for Pregnancy Endpoints) has looked at tests that may help to predict adverse outcomes including preeclampsia. The SCOPE study has been led by the University of Auckand and one of SCOPE's principle investigators is Professor Lesley McCowan who is the HOD for O&G.

Activity: Prediction by risk factors

So what are the factors that may influence the likelihood for developing preeclampsia ? Have a look at the list below and decide whether these factors increase or decrease the risk You may like to have a look at the table at the beginning of this section and also the the BMJ paper in your readings.

Clinical risk factors provide some information to help predict preeclampsia but research goes on to improve our prediction models. Uterine artery Doppler studies (telling us about resistance in the uteroplacental circulation) at 20 and 24 weeks has been shown to be additional in risk prediction in women with clinical risk factors but is not useful for a general population. Studies are concentrating on angiogenic biomarkers such as placental growth factor (PlGF), vascular endothelial growth factor (VEGF) and s-Flt in maternal blood that may be present at abnormal levels before the onset of disease. The most promising candidate seems to be PIGF or PLGF/s-Flt ration.  Hopefully within the next 5-10 years we will have a more reliable prediction test to allow us to triage women for levels of antenatal care dependent on their risk.

Prevention of preeclampsia

Once women have been identified to be at risk of preeclampsia are we able to prevent the disease?

Large meta-analyses of several randomised controlled trials show that aspirin (100 mg daily) started before 20 weeks results in a 10-20% reduction in women at high risk of preeclampsia. It is likely that most benefit is gained if asprin is taken in the evening or at bedtime rather than in the morning. Calcium (1.5g daily), particularly for those women with low dietary calcium and at high risk, results in 50% reduction. Antioxidants are not effective. Additional therapies currently being investigated as preventative treatments include; low molecular weight heparin pregnancy multivitamins and folic acid.

As is usual, the diagnosis is made with the help of the history, examination and investigations. Have another look at the previous table showing the features of preeclampsia. Think about the presentations that you will be looking out for in the history and examination and relate them to each organ involved or potentailly involved with the disease (cardiovascular, renal, hepatic, haematological, neurological, peripheral and pulmonary vessels, placental and fetal).      

Here are some guides for you to follow:-   

In the future it is likely that tests such as PlGF and  PLGF/s-Flt ratio may be used to identify those women who develop GH or preeclampsia and are at most risk of having an adverse pregnancy outcome.  However, at present we recommend all women should be managed as in-patients as it is difficult to predict the time-course, severity and risk of complications of the disease.

Treating hypertension will reduce the risk of severe hypertension developing but does not alter the time course of the disease. Blood pressure treatment should be considered if persistent BP of ≥150/95 mmHg. Treatment of severe hypertension is likely to reduce the risk of cerebrovascular accident. First line options of antihypertensives include: methyldopa, labetalol (not atenolol which may affect fetal growth) and nifedipine. ACE inhibitors are contraindicated in pregnancy. For acute severe hypertension: oral nifedipine, iv hydralazine and iv labetolol may be given. Women who experience an eclamptic seizure or who are at risk of one (severe hypertension, symptoms, brisk reflexes, ≥2 beats of clonus) should receive magnesium sulphate. Any women requiring magnesium sulphate or with evidence of multisystem organ involvement should be managed in a high dependency setting.

The timing of delivery will depend on the gestational age at presentation and the severity of the disease. It is important to remember that in women with early onset disease it is more likely to be severe and involve the fetus as well. The only real ‘cure' for preeclampsia is delivery of the baby and the placenta but this must be weighed against the risks of delivery for both the mother (need for induction of labour or caesarean section) and the fetus (prematurity). Preeclampsia can still present postnatally and continued close surveillance is necessary. 40% of eclamptic seizures occur after delivery.