Hypertension in pregnancy affects approximately 10% of women. The reported incidence varies between studies, but it is estimated that 1.3-3% of pregnant women will have chronic hypertension (Sibai, 2002; Roberts et al, 2008; Bateman et al, 2012) and 8.3% will have gestational hypertension (Roberts et al, 2008). The number of women entering pregnancy with chronic hypertension is rising, predominantly because of increasing rates of obesity and pregnancy at advanced maternal age (Seely and Ecker, 2011). Women with chronic hypertension can be sub-divided into those with essential hypertension (ie with no known secondary cause) and hypertension secondary to another medical condition. ‘Chronic hypertension’ is often used interchangeably with the term ‘pre-existing hypertension’, but it is important to remember that a significant proportion of women are newly diagnosed in pregnancy.
The National Institute for Health and Care Excellence (NICE) (2010) provides the following definitions of hypertension in pregnancy:
Women with chronic hypertension are at risk of their hypertension becoming severe in pregnancy, putting them at risk of stroke, deranged liver function and low platelet levels, and their babies may be subject to low birth weight and preterm birth (Magee et al, 2016). Women with chronic hypertension have a 25.9% risk of developing pre-eclampsia (Bramham et al, 2014) compared to 2-8% in the general population (Royal College of Obstetricians and Gynaecologists (RCOG), 2012). In addition to the above risks, pre-eclampsia may develop into eclampsia and HELLP (Haemolysis, Elevated Liver enzyme, Low Platelet) syndrome. Pre-eclampsia puts a woman at increased risk of long-term consequences such as heart failure, coronary heart disease, stroke, disease from cardiovascular causes, and venous thromboembolism (Bellamy et al, 2007; Wu et al 2017). Women with superimposed pre-eclampsia are at a higher risk of future cardiovascular disease compared to women with chronic hypertension or pre-eclampsia alone (Ying et al, 2018). Studies also demonstrate a higher rate of caesarean sections and high-dependency care in pregnancy among women with chronic hypertension (Webster et al, 2017).
Severe hypertension and superimposed pre-eclampsia contribute significantly to the UK's stillbirth rate. In 2018, the overall stillbirth incidence in this population was 1.6% (compared with a background UK stillbirth rate of 0.4%). This increased five-fold in black women with chronic hypertension compared to white women with chronic hypertension (Webster et al, 2018a). Identifying and effectively managing hypertension in pregnancy is critical in contributing to the drive to reduce stillbirths by 50% in England by 2025 (de Bernis, 2016; O'Connor, 2018). These risks are considerably higher than those associated with gestational hypertension and so differentiation between these is important.
Hypertension is potentially a significant modifiable risk factor (NICE, 2016a; Olsen et al, 2016). The midwife is in an ideal position to improve the care of pregnant women with chronic hypertension. This article reflects on and explores the ways in which a midwife might provide support. It outlines the critical role of the midwife in the accurate and prompt identification, assessment, referral and care of women with chronic hypertension in pregnancy.
Identifying women with chronic hypertension
Diagnosis of hypertension outside of pregnancy
It is important that the midwife takes a thorough history of past and present hypertensive disorders, including medication history. The purpose is to differentiate between a history of chronic hypertension, a history of gestational hypertension in a previous pregnancy, and a history of pre-eclampsia in a previous pregnancy. It is important to note that even if a woman's blood pressure is controlled with medication, her diagnosis of chronic hypertension means that her pregnancy continues to be deemed higher-risk. Women who book with a history of hypertension outside of pregnancy should receive a prompt referral to their obstetric consultant for assessment and an individualised management plan.
Identifying chronic hypertension for the first time in pregnancy
As hypertension is predominantly asymptomatic and pregnancy may be the first time a woman has her blood pressure checked, a proportion of women will be identified as having hypertension for the first time during pregnancy. Although blood pressure may fall by a small amount, this is not likely to be substantial, and women presenting with high blood pressure before 20 weeks' gestation are therefore likely to have chronic hypertension. If a woman has sustained systolic BP ≥140 mmHg and/or diastolic BP ≥90 mmHg, this is classified as hypertension and they should be referred for obstetric review (NICE, 2019). Although there is no absolute definition for ‘sustained’, the term may refer to repeated blood pressure measurements over the threshold during one appointment, or if high readings were obtained on more than one occasion.
Midwives should use their discretion if assessing a woman whose borderline blood pressure is at the higher end of normal, but does not meet the definition of hypertension. Consideration should take into account whether the woman has any other risk factors that may place her at higher risk of hypertension or pre-eclampsia in order to assess whether referral to the obstetrician would be beneficial. It may be appropriate to undertake more regular blood pressure measurements. This could either be done through extra antenatal appointments, or by using the GP or the maternal assessment unit.
Identifying severe hypertension in pregnancy
If a woman presents with severe hypertension (≥160/110 mmHg), immediate referral should be made for treatment (NICE, 2010). The Confidential Enquiries into Maternal Deaths report (Cantwell, 2011) stated that a major failing in clinical care was inadequate treatment of hypertension, with subsequent intracranial haemorrhage. Despite a marked fall in maternal deaths related to hypertension in the past two decades, failing to promptly treat severe hypertension continues to contribute to maternal mortality (Knight et al, 2014).
Identifying a woman with chronic hypertension
Accurately assessing blood pressure
It is important to consider the multiple factors that may influence a pregnant woman's blood pressure readings, such as the use of manual compared to electronic devices, and clinic vs at-home readings.
The device
Mercury sphygmomanometry remains the gold standard for recording blood pressure in pregnancy, although this technique is increasingly unavailable due to mercury being phased out over toxicology concerns (Tranquilli et al, 2014). Aneroid devices (devices without liquid) are commonly used, but evidence suggests that some may be inaccurate by more than 10 mmHg and need to be regularly calibrated (Brown et al, 2018). The use of automated devices is increasing, but they need to have undergone a validation process to assure their accuracy (Stergiou et al, 2018). Pregnancy, hypertension and pre-eclampsia result in distinctive haemodynamic and vascular changes thought to affect blood pressure readings (Bello et al, 2018). Dabl Educational Trust (2019) provides an online resource where you can find latest information on validated blood pressure devices in different populations. It is worth noting that only a small number of automated blood pressure monitors have been validated in both pregnancy and pre-eclampsia (Nathan et al, 2015). Arguably, any blood pressure device used by a midwife should be validated in normotensive, hypertensive and pre-eclamptic pregnant populations to be considered accurate and appropriate to measure the blood pressure of any pregnant woman whom a midwife may encounter.
Technique of blood pressure measurement
Midwives should ensure that a blood pressure cuff is appropriately sized for a woman, as both under-cuffing or over-cuffing might result in inaccurate readings (with a too small cuff giving falsely high readings). If a variety of cuffs are unavailable, the preference should be to over-cuff (Nathan et al, 2015). The American Heart Association (2016) provides an infographic showing the correct way to take blood pressure. Previously, cuff size was not considered in the validation of blood pressure devices; however, updated guidance will advise that devices should be tested with all cuff sizes. New research is demonstrating that the shape of the arm may also affect the accuracy of the readings taken (Palatini and Asmar, 2018). The woman should not be talking, her arm should be supported, with the forearm at the level of the heart (O'Brien et al, 2003); she should be seated comfortably with her legs uncrossed and have an empty bladder (Pickering et al, 2005).
Self-monitoring of blood pressure
Self-monitoring of blood pressure is increasingly popular with pregnant women and health professionals; around one-third of people with hypertension in the non-pregnant population self-monitor and studies show that measurements taken at home are better associated with long-term adverse outcomes than clinic blood pressures (Hodgkinson et al, 2011). Anecdotal reports in the UK suggest self-monitoring in pregnancy is also commonplace, although no published studies have assessed this (Baral-Grant, 2012). It is unknown whether self-monitoring of blood pressure has positive, negative or negligible effects on pregnancy outcomes (Hodgkinson et al, 2014); therefore, there is a need for high-quality evidence to assess the potential impact of self-monitoring blood pressure in pregnancy (Lavallee et al, 2018). Evidence from the general hypertensive population demonstrates that self-monitoring of blood pressure has a greater effect on blood pressure control when used in combination with other interventions, such as self-titration of medication (McManus et al, 2010).
Accurate assessment of blood pressure
Blood pressure control
NICE (2010) recommends that blood pressure should be kept ≤150/100 mmHg. For women with target-organ damage secondary to their hypertension, such as those with kidney disease, the aim should be to keep blood pressure ≤140/90 mmHg. Since the NICE guidelines were published in 2010, a large international randomised controlled trial (Magee et al, 2015), was published. The study randomised women with pregnancy hypertension to either ‘tight’ (target diastolic pressure of 85 mmHg) or ‘less tight’ (target diastolic pressure of 100mm/Hg) control of blood pressure. Although no difference was found in the primary outcome of pregnancy loss or high level neonatal care, tight control of blood pressure led to a significant reduction in the incidence of severe hypertension for all women with chronic hypertension, with no evidence of perinatal harm. Women with chronic hypertension may need more frequent antenatal visits due to unpredictable gestational changes in blood pressure, particularly if medication needs to be changed or increased.
Blood pressure control
Frequency of blood pressure measurement
NICE antenatal care guidelines recommend that blood pressure is measured at each antenatal contact for every pregnant woman (NICE, 2019). To diagnose hypertension, it is recommended that a blood pressure measurement should be repeated (Brown et al, 2018). If blood pressure is severe (systolic BP ≥160 and/or diastolic BP ≥110 mmHg), then the blood pressure should be confirmed within 15 minutes. For less severe blood pressure, repeated readings should be taken over a few hours. Despite the existence of a recommended schedule of care for low-risk women in pregnancy, there is no guidance on frequency of visits for those with additional risk factors, and any extra antenatal consultations should be based on the individual needs of both the woman and her baby (NICE, 2010). During labour, blood pressure should be measured at least hourly, or more frequently if unstable (NICE, 2010).
Frequency of blood pressure measurement
Antihypertensive medication
Although it is not the midwife's primary role to manage antihypertensive treatment during pregnancy, it is beneficial to be aware of which medications are contraindicated. NICE does not specify a first-line antihypertensive agent for the treatment of pregnant women with chronic hypertension due to the limited availability of evidence, but labetalol, nifedipine and methyldopa are commonly used. Individual medication decisions should consider the woman's pre-pregnancy medication, safety profile and potential teratogenicity (Webster et al, 2018a). There may be an increased risk of congenital abnormalities if angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) (Box 1) are taken during pregnancy (NICE, 2010). Additionally, if women are taking the diuretic chlorothiazide, there may be an increased risk of congenital abnormalities and neonatal complications (NICE, 2010). If there is likely to be a wait of more than 2 days for an obstetric appointment, midwives should ensure prompt referral back to the GP to change medication (NICE, 2010).
| ACE Inhibitors | ARBs |
|---|---|
| Enalapril | Candesartan |
| Lisinopril | Irbesartan |
| Perindopril | Losartan |
| Ramipril | Valsartan |
Anti-hypertensive medication
Superimposed pre-eclampsia
Superimposed pre-eclampsia is the development of pre-eclampsia in women with chronic hypertension and is associated with significant maternal and fetal morbidity. The midwife plays an important role in the prevention, identification and management of the condition.
Prevention
Aspirin may reduce the risk of developing superimposed pre-eclampsia. NICE guidelines recommend that a woman takes 75 mg aspirin daily from 12 weeks' gestation until the birth of her baby if she is diagnosed with chronic hypertension (NICE, 2010). Starting aspirin before 16 weeks' gestation has been demonstrated to significantly reduce the risk of pre-eclampsia for women at risk. This benefit may be reduced if started after 16 weeks' (Bujold et al, 2010), highlighting the importance of early identification and referral. Despite NICE recommendation and widespread awareness of the benefits of aspirin in the prevention of pre-eclampsia, pharmacies are not licensed to sell pregnant women aspirin, and therefore midwives should ensure that women see their GP or obstetrician by 12 weeks' gestation for a prescription.
Recognition
Midwives play an important role in identifying superimposed pre-eclampsia in women with chronic hypertension and preventing morbidity. Midwives need to be vigilant in considering additional signs or symptoms that should prompt investigation for pre-eclampsia. Women themselves can also play a key role in identifying superimposed pre-eclampsia; however, Carter et al (2017) found that many women diagnosed with pre-eclampsia did not have an understanding of the condition or its implications for the health of the baby or themselves. Many were also unaware of signs and symptoms of pre-eclampsia until after their initial diagnosis. Midwives should ensure that all women are aware of the risks, signs and symptoms of pre-eclampsia and the importance of regular antenatal checks in its detection and management. Women should be asked about signs and symptoms for pre-eclampsia at each antenatal appointment (NICE, 2019); however, women may not always present with ‘classic’ symptoms, or be able to distinguish these from normal pregnancy characteristics (Carter et al, 2017). Symptoms of pre-eclampsia include (RCOG, 2012):
Women on anti-hypertensive medication may have a blood pressure <140/90 mmHg but still have the disease. The addition of just one of the factors below should be recognised as pre-eclampsia (Brown et al, 2018):
Superimposed pre-eclampsia
The role of the midwife in the multidisciplinary team
Although an obstetrician should be the lead professional for women with additional risk factors in pregnancy, for almost all pregnant women, the midwife is the conduit for care throughout pregnancy, labour and the postnatal period (NHS Education for Scotland, 2010). The woman may have multiple hospital appointments and midwives should consider this when organising to see women for routine antenatal care. These additional appointments with other members of the multidisciplinary team should not replace normal midwifery care. Better Births (National Maternity Review, 2016) highlights the importance of effective multidisciplinary working to safe, women-centred care.
When discussing birth plans, it is likely that the woman will have an obstetric plan in place, in terms of both timing and mode of birth. Although women with controlled hypertension and no additional risk factors should not be offered delivery before 37 weeks' gestation, they may have a plan for birth between 38-40 weeks' (NICE, 2010). The role of the midwife in providing tailored birth information and support is still vital.
Women with uncontrolled blood pressure in pregnancy may have been advised to have an early planned birth, and therefore discussions with the women should reflect this, preparing her for possibility of the baby going to the neonatal unit. Normal discussions about infant feeding are encouraged, and women planning to breastfeed should be reassured that their antihypertensives will be safe.
The role of the midwife in the multidisciplinary team
Postnatal care
Midwives should monitor women with chronic hypertension closely in the postnatal period. Blood pressure usually falls immediately after giving birth and then tends to rise, reaching a peak 3–6 days postpartum (Bramham et al, 2013). Blood pressure should be monitored daily for the first 2 days after birth and at least once between postnatal day 3 and 5 (NICE, 2010), and referral for a review should be made if a woman's blood pressure is over 140/90 mmHg. Medication should be reviewed after birth to ensure that it is safe for breastfeeding. Diuretic treatment in the postnatal period should be avoided in women who are breastfeeding or expressing milk, and particular attention should be paid when antihypertensive medication has been changed to ensure the blood pressure remains well controlled.
Safety antihypertensives for babies receiving breastmilk with no known effects include (NICE, 2010):
There is insufficient evidence for the safety of ARBs, amlodipine and ACE inhibitors (other than enalapril and captopril) for babies receiving breastmilk (NICE, 2010).
Medication should be continued and reviewed 2 weeks after birth (NICE, 2010). Women should be advised to continue to see their GP for management of their blood pressure postnatally, due to the long-term benefits of maintaining a well-controlled blood pressure (NICE, 2016a).
Given the other pressures on a new mother, changing to an antihypertensive medication regimen that is suitable in breastfeeding and that can be taken once per day should be considered. Methyldopa should ideally be discontinued (if an alternative can be found) due to its association with low mood (NICE, 2010)
Postnatal care
Caring for pregnant women with chronic hypertension in practice
Box 2 shows hypothetical scenarios, based on experiences in practice.
| Example | Issues |
|---|---|
| Tanya was pregnant with her first baby and booked with her community midwife at 7 weeks' gestation. Her blood pressure was initially 139/102 mmHg but 126/86 mmHg on repeat. She was referred for a consultant appointment after 20 weeks' gestation because her BMI was 35kg/m2 |
|
| Joanna had chronic hypertension for several years but her blood pressure was well controlled on medication during her pregnancy. At 32 weeks' gestation, the midwife documented that Joanna was complaining of headaches. ‘No spec’ was documented in the urinalysis box |
|
| Shaparak was diagnosed with chronic hypertension when she was 16 weeks' pregnant. She had induction of labour at 38 weeks' because her blood pressure was noted to be high during a routine clinic visit. Her antihypertensive medication was stopped after the birth as her BP was normal. She was discharged to the community midwives on day 2 but was not seen again until day 5 when her BP was 163/110 mmHg |
|
Women with chronic hypertension are at high risk of maternal and fetal morbidity and mortality, but despite these statistics, few units provide specialist care for these women. This is starting to change, however, with large tertiary centres providing specialist services.
An example of a specialist service: hypertension in pregnancy clinic
The hypertension in pregnancy (HiP) clinic at Guy's and St Thomas' NHS Foundation Trust was set up in response to a local audit that demonstrated suboptimal outcomes for women with chronic hypertension, particularly for women with complex needs (NICE, 2016b). A local needs analysis found that the existing system was not significantly robust to provide high-quality care for these women. Changes were made to local guidelines for hypertension in pregnancy and a specialist HiP service was set up. Critical to establishing the clinic was the involvement of women in its development. A patient and public involvement research group was set up to gain an understanding of what was important to women and the opportunities for improvement. Issues raised included the gaps between services (particularly communication across the different parts of the service and between primary and secondary care); a lack of recognition of the condition (for example, if a woman with chronic hypertension is assessed as having a normal blood pressure while taking antihypertensive medication), and lack of appropriate action (such as timely referral of women with high blood pressure out of target range).
Confidential enquiries highlight that a lack of communication, ownership and joined up care are major contributing factors to poor outcomes (Knight et al, 2014). The HiP clinic is operated by a multidisciplinary team of obstetricians, obstetric physicians and midwives who have a specialist interest in hypertension in pregnancy, and attempts to improve care by providing co-ordinated support, treatment and information during and after pregnancy. The NICE (2013) quality standard on hypertension in pregnancy was used to underpin the service and encompasses eight quality statements:
Women's needs were reviewed before the establishment of the service, which identified how the lack of a specialised midwifery team for women with chronic hypertension contributed to fragmented care and ineffective follow up after missed appointments. An existing team of midwives at the Trust, whose remit included high-risk women, agreed to care for women with chronic hypertension. Women who have chronic hypertension at the time of referral for their pregnancy are booked by this team, and continue to see the team for their normal midwifery care. The team undertake their midwifery clinic alongside the HiP clinic, where there is immediate access to the obstetricians if there is concern about a woman's hypertension. The midwives develop expertise and experience in caring for these women, including their complex medical and social needs, and provide continuity, which is known to improve pregnancy outcomes (Sandall et al, 2015).
Obstetricians see the women as soon as possible after they enter the service (usually within 1 week) to ensure appropriate counselling and formulation of an individualised plan of care. Baseline tests, including a urine protein-creatinine ratio, renal and liver profile, and electrocardiogram are conducted as early as possible to identify any further pre-existing issues or other cause for the hypertension. Due to the additional scans recommended, dedicated scanning appointments are scheduled at the same time as the clinic, to minimise the amount of time the woman has to spend in the hospital. Research midwives form part of the integrated team; at any one time, several clinical studies focused on hypertension in pregnancy are often being offered to women in the clinic as part of their routine care. At the end of each clinic, there is a case review where all the health professionals caring for the woman share new information or concerns.
The HiP clinic has been received positively, but this is just one way in which the needs of pregnant women with chronic hypertension could be addressed. Although initially there was concern about de-skilling of health professionals, there has been wider recognition of the likely benefits of care for certain high-risk groups, such as women with pre-existing diabetes or epilepsy. Further research on the benefits of joint multidisciplinary team clinics for women with complex conditions is needed (Bick et al, 2014). Robust research into the optimal set-up and outcomes of these clinics is needed to provide a strong evidence base for their wider implementation. It may be necessary to adapt this model for different settings, but the NICE (2013) quality statements may provide a framework to benchmark care for women with chronic hypertension.
Conclusion
Chronic hypertension is known to increase the risks in pregnancy for both the mother and the fetus, yet there is significant potential for a midwife to positively affect the care of these women and improve outcomes. This is a complex area, often due to varying needs and medical comorbidities, with a lack of strong evidence base. Emerging research is continuing to shape the guidelines of care for women diagnosed with chronic hypertension. Although these women's care should be led by an obstetrician, midwives are integral to prompt referral, ongoing assessment and provision of underpinning care in her pregnancy (National Maternity Review, 2016). This may be achieved by building on midwives' knowledge and understanding of chronic hypertension, its risk in pregnancy and when, why and how women should be referred for additional care.