This week is “Know your numbers week”, a campaign to encourage the public to be aware of their blood pressure results and checking on it regularly for good health. For midwives blood pressure is an important measurement for maternal and fetal wellbeing. Lisa Cook, Specialist Midwife for Maternal Medicine, Royal Preston Hospital, reminds us of the significance of blood pressure measurement and best practice of good care.
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Hypertension and pre-eclampsia are pregnancy complications familiar to all midwives and clinicians working in maternity care. Globally, 40,000 women die each year from Eclampsia, with 5 women losing their lives to complications of pre-eclampsia every hour (WHO, 2024,) Whilst these figures represent many developing countries, here in the United Kingdom (UK) and Ireland, maternal, fetal and neonatal morbidity and mortality remain at rates which should drive Midwives and other clinicians to learn more about the prevention, detection and management of these complex disease pathways (MBRRACE-UK, 2023, Ockenden 2022). Around 400BC Hippocrates discussed the symptoms of headache, heaviness and convulsions in some pregnant women. We are familiar with Eclampsia, the Greek work for lightning, to describe the sudden tonic-clonic seizures diagnostic of this life-threatening condition. Thankfully, the use of magnesium sulphate to prevent and manage these seizures has reduced maternal morbidity and mortality and is now embedded in practice across the globe. Eclampsia is associated with haemorrhagic stroke, cerebral vasospasm and oedema (Judy et al, 2019). Around a third of women will have an eclamptic seizure before they develop hypertension and proteinuria. Teenagers are three times more likely to experience a seizure then their older counterparts (Nelson-Piercy, 2021). Each midwife and clinician working in maternity care should become familiar with local and national guidelines on the prevention and management of eclampsia.
Here in the UK, hypertension and pre-eclampsia account for the most common clinical indication for admission to hospital, as well as frequent out-patient attendance to antenatal assessment areas and maternity triage units, where the onus of management often lies with the duty team, making consistency and continuity of care, care planning and management a challenge. Maternal mortality from hypertension and pe-eclampsia is largely avoidable. The MBRRACE-UK report (2023) highlights that improvements in the care of almost 50% of women who died would have made a difference to the outcome. This is a sobering statistic in the 21st century National Health Service. Ninety-six percent of the women who suffered an intracranial bleed were known to have systolic hypertension.
The regular and accurate recording of blood pressure on a pregnancy validated electronic device, using an appropriately sized cuff is fundamental in detecting rises in blood pressure. Blood pressure (BP) should be taken following several minutes of sitting quietly, with both feet flat on the floor and the machine at chest level in the clinic setting (Action on Pre-Eclampsia e-learning module). BP recordings should be compared to the earliest possible BP recording available (usually the booking BP). Pulmonary oedema, whilst occurring spontaneously in some cases, remains largely iatrogenic, highlighting the need for midwives to be skilled and accurate in their management of fluid balance. Careful recording of all intravenous (IV) crystalloids, blood products, IV medications and oral intake should be accurately recorded alongside insensible loss, PV loss, vomit, wound drain and accurate urine output measurement, to ensure the risk of developing pulmonary oedema is minimised, whilst ensuring adequate renal and other organ perfusion.
Whilst hypertension and pre-eclampsia have wide reaching implications for maternal health, the risks to the growing fetus cannot be underestimated. Each year in the UK, around 1000 babies are lost due to pre-eclampsia, many through the complications of pre-term birth (APEC 2024). Maternal and fetal surveillance must go hand in glove to ensure decisions around the timing of birth support the best possible outcome for mothers/birthing people and their babies. The use of ultrasound scans measuring uterine artery dopplers, liquor volume and growth have improved outcomes for babies (SBL v3). There are some clinical situations where maternal disease is so severe that it necessitates extremely early birth, and women and birthing people and their families must receive adequate information and support during and after this harrowing time. Thankfully, these situations, whilst difficult for all concerned, are not commonplace in terms of the overall numbers of hypertension and pre-eclampsia seen in daily practice.
Midwives are at the forefront of maternity care and are ideally placed to support the prevention, detection and management of hypertension and pre-eclampsia. The initial contact at the booking visit identifies genetic, environmental and lifestyle factors that may indicate an increased risk of pre-eclampsia. Women and birthing people may report a previous/family history of pre-eclampsia/eclampsia, renal disease, chronic hypertension or insulin dependent Diabetes Mellitus. These conditions result in vascular dysfunction which in turn increase the chance of developing pre-eclampsia as the pregnancy progresses. Environmental factors such as increased birth interval (>10 years), increased maternal age as well as lifestyle choices including smoking, high dietary sodium intake (strong association with chronic hypertension, APEC 2024) and high Body Mass Index (BMI, >35), all alert the midwife to the need for accurate risk assessment for a safe, evidence based ongoing plan of care. An essential part of the booking visit is the accurate recording of maternal blood pressure. The earlier this is recorded in pregnancy, the closer it will reflect the true maternal cardiovascular condition. It will then serve as a comparison for all subsequent BP recordings if there is a suspicion of gestational hypertension or pre-eclampsia. Urinalysis is also a simple yet essential procedure that will help early identification of pathology and serve as a baseline for the weeks to come. The exclusion of renal causes for any proteinuria or hypertension identified at booking can be supported by taking a blood sample for urea and electrolytes and a urine protein-creatinine ratio. This will aid ongoing care and the exclusion/diagnosis of background disease.
Midwives are excellent at discussing fetal surveillance in the form of observation of fetal movements and the signs and symptoms of pre-eclampsia. These discussions should continue throughout the pregnancy journey. A blood pressure of 130/80mmhg in a young person is not normal and warrants further investigation (Wenger et al, 2018). The ongoing aim in the management of gestational hypertension and pre-eclampsia is to maintain a BP of 140/90mmhg or less and 135/85mmhg in the presence of renal disease.
Midwives are increasing encountering women/birthing people at the booking visit who are already on anti-hypertensive medication. This is usually in the form of Angiotensin converting enzyme (ACE) inhibitors such as Ramipril. ACE inhibitors are contra-indicated in pregnancy due to their link with fetal abnormalities and neonatal issues (UKtis), so arrangements should be made to safely change to a medication suitable for pregnancy, such as Labetalol or Nifedipine/Amlodipine (NIHR APEC 2019). The use of Aspirin has been a game changer in the prevention and management of preeclampsia since the Clasp trial (1994). Aspirin reduces the incidence of pre-eclampsia in high risk pregnancy (Atallah et al, 2017) and midwives and clinicians should be familiar with their local guidance on its use. Many units have patient group directives in place to allow midwives to prescribe Aspirin to women identified at high risk from 12 to 36 weeks gestation. An assessment of each person’s venous thromboembolism risk should also be calculated at the booking visit as women/birthing people are at increased risk of VTE due to endothelial damage, stasis of blood flow and the hypercoagulable state of pregnancy as discussed in Virchows triad ( Pavord & Hunt, 2018). Supra-imposed hypertension/pre-eclampsia further increase this risk. The VTE risk assessment should be revisited and reviewed as the pregnancy progresses. The pathology of pre-eclampsia is established in the first trimester but may not manifest until much later in the pregnancy. Pre-eclampsia can only be diagnosed after twenty weeks gestation, but often does not present until term. In a healthy pregnancy, adequate placentation takes place and vascular endothelial growth factors (VEGF) are released. This stimulates blood vessel growth (angiogenesis) for the developing placenta and embryo to establish the pregnancy and support its continuation. Placental growth factor (PlGF)is a protein also involved in placental angiogenesis, which rises as the pregnancy progresses and peaks at around 28-32 weeks gestation, after which it steadily falls until term. When there is abnormal placentation, or high placental demand, for example, with multiple pregnancy, the placenta becomes ‘stressed’. This results in the release of pro-inflammatory cytokines. Inflammation results in cell wall damage and increased vascular permeability. This occurs concurrently with widespread vasoconstriction, impaired vasodilation and systemic hypoperfusion causing multi-organ damage. This pathology is manifested clinically in the symptoms women/birthing people report and in abnormal biochemistry and haematology blood results and urine tests. The ‘stressed’ placenta also releases the protein Soluble FMS-like tyrosine kinase-1(sFlt-1). This is thought to disable proteins associated with angiogenesis, such as PlGF, by binding to it, thus reducing the amount available for angiogenesis. sFlt-1 is present in healthy pregnancies and rises throughout the pregnancy until term. In a pregnancy with abnormal placentation, sFlt levels are much higher and these higher levels are detectable up to five weeks before the symptoms of pre-eclampsia present. A PlGF level of above100 indicates a healthy pregnancy, between 12-100 is a low level and below 12 indicates pre-eclampsia. A rising sFlt-1 level and a falling PlGF is an ominous sign, so looking at the ratio between the two biomarkers is a good clinical indication of the level of disease.
Early onset pre-eclampsia, that is, occurring before 34 weeks gestation, is secondary to inadequate establishment of placental perfusion in early pregnancy. It is placentally driven disease. This disease process has significant implications for fetal wellbeing as it causes fetal growth restriction(FGR) – a clinically small baby may be identified before maternal symptoms of pre-eclampsia present. This further supports the need for accurate risk assessment at booking and subsequent midwifery contacts. Early onset pre-eclampsia also has implications for ongoing maternal health. The risk of cardiovascular disease in later life for these women is significant and requires closer surveillance by primary care services.
Late onset pre-eclampsia, after 34 weeks gestation, is driven by the demand on the placenta. Whilst there is no placental malperfusion or FGR, the increased demand on the placenta exceeds its capacity – think of a plant that has become pot-bound. This results in placental stress and the pathophysiology discussed gives rise to maternal symptoms and disease progression. Maternal inflammation, endothelial damage and organ ischaemia give rise to the classic yet varied symptoms we see women/birthing people present with in practice. Symptoms may be as vague as feeling tired, unwell or anxious, or experiencing some nausea/vomiting, or more indicative of a diagnosis of pre-eclampsia with epigastric or right upper quadrant pain from liver ischaemia, visual disturbances/blindness from papilloedema, or generalised oedema. More unwell women/birthing people may present with significant neurology from raised intracranial pressure such as severe headache, altered AVPU, seizures, and cerebral haemorrhage. Proteinuria and reduced urine output may be identified and blood tests may reveal a high creatinine level or acute kidney injury. Liver function tests and full blood count should be monitored, and clinicians should be alert to the risk of haemolysis of red cells, leading to anaemia, elevated liver enzymes indicating liver cell damage and low platelets, increasing the risk of bleeding. Together these are known as HELLP syndrome. This pathology indicates worsening disease and plans for birth should be discussed and initiated, with the woman/person at the centre of the decision-making process.
The Midwife is well placed to advocate for families in these complex situations. Clinicians should discuss evidence to support birth planning, such as the Phoenix trail (Chappell et al, 2019), to aid the decision making process where clinically appropriate. Alongside close monitoring of maternal bloods, sFlt-1:PlGF ratio and ultrasound fetal surveillance, medication is further tool in the management of pre-eclampsia. Whilst medication treats a symptom, not the cause of this complex disease, it offers protection to the maternal physiology. The careful and appropriate use of anti-hypertensives will often mean that the pregnancy can be prolonged to maximise in-utero time for the baby as well as control risk to the mother/person. Treatment should be with Beta-adrenoreceptor antagonists (known as Betablockers) such has Labetalol (not to be used in asthma), up to a maximum of 2.4grams/24hours, or calcium channel blockers such as Nifedipine (max 80mg/24hours) or Amlodipine (max 10mgs/24hours). Alpha-blockers such as Methyldopa and Doxazocin can also be used if other drugs are ineffective. Women and birthing people may require more than one agent to manage their hypertension. Management of women and birthing people with pregnancies complicated by hypertension and pre-eclampsia involve intensive and complex plans of care, to which the midwife is front and centre.
The development of specialist clinics for the care of these families provides continuity, oversight and specialist care. This reduces pressure on the duty team in managing fetal and maternal wellbeing and provides a ‘one stop shop’ for care. Specialist clinics can facilitate home monitoring of BP, which most women/birthing people find more acceptable than long waits in busy maternity assessment units. Midwives are uniquely placed to develop these clinics and senior leadership should support their implementation.
Whilst the main focus of care around pre-eclampsia takes place in the antenatal period, midwives are again at the forefront of postnatal care, and ongoing care in the postnatal period is essential for safe care. Thirty-eight percent of eclamptic seizures occur in the postnatal period. Ongoing blood pressure surveillance and medication management are a fundamental principle in the postnatal period for women/birthing people with increased risk. Blood pressure falls following birth and then rises to a peak at day 3-5 post birth. This is often after discharge from hospital, so midwives need to remain vigilant. Any medications commenced in pregnancy should be switched to once daily medications to aid compliance. Enalapril is a safe and effective drug taken once daily. Renal function should be assessed one week after starting Enalapril. Women and birthing people discharged home on medication should have their blood pressure monitored at least once on day 3-5 and then alternate days until day 14 when they should have a GP review. A clearly documented postnatal plan should be made prior to discharge, with clear BP parameters documented to guide care. Home blood pressure monitoring can replace midwifery visits from day 5 if the woman/birthing person is well and the midwife has the ability to review blood pressure recordings. For those who were hypertensive during pregnancy but discharged without medication, a 6-8 week GP follow up should be carried out. Midwives should continue to give lifestyle advice around smoking, weight control, diet and exercise to reduce future cardiovascular risk. Good postnatal care is the pre-conceptual care for the next pregnancy and will enable women and birthing people to embark on a future pregnancy in optimum physical and emotional health.
Hypertension and pre-eclampsia are a common pregnancy complication seen in midwifery practice. Midwives are at the forefront of the prevention, detection and management of this complex disease process and should be vigilant to recognise the often-subtle signs and symptoms of disease progression. Maternal and fetal surveillance go hand in glove and should include regular BP monitoring, urinalysis at every contact, maternal blood tests where indicated, fetal ultrasound and specialist care and follow up.
Lisa Cook,
Specialist Midwife for Maternal Medicine, Lancashire Teaching Hospitals Maternal Medicine Centre, Royal Preston Hospital
August 2024