Key learning points:
– Effective referral upon identification of raised blood pressure is essential for reducing adverse pregnancy outcomes
– Few automated monitors are currently validated for use in pregnancy and pre-eclampsia
– Postpartum psychosocial support and counselling about subsequent cardiovascular risk is important following hypertensive pregnancy
Worldwide, 10% of women have high blood pressure (BP) during pregnancy, defined as more than 140/90mmHg.1 Hypertensive disorders during pregnancy may result in substantial maternal morbidity and are a leading cause of direct maternal deaths in the UK. They also carry a risk for the baby, resulting in 8-10% of all preterm births.2 Women with severe pre-eclampsia are likely to give birth preterm3 and pre-eclampsia is strongly associated with fetal growth restriction, low birth weight, preterm delivery, respiratory distress syndrome, and admission to neonatal intensive care.4 Finally, the long-term outcomes for women with a diagnosis of hypertension in pregnancy include an increased likelihood of chronic hypertension and increased lifetime cardiovascular risk.5 Hypertension in pregnancy is defined in Box 1.
This article aims to provide an up to date guide about best practice in managing women with hypertension in pregnancy for community midwives along with the latest research in the field. Risk factors and the management of hypertension in pregnancy, together with its effects on outcome and how a woman’s experience can be affected is covered in this article.
Risk factors
Current National Institute for Health and Care Excellence (NICE) guidelines recommend blood pressure monitoring at routine antenatal visits with ‘increased frequency’ in those at higher risk.6 NICE states that women with any of the risk factors below are considered to be at higher risk:6
1. Aged 40 years or older.
2. Nulliparity (first pregnancy).
3. Pregnancy interval of more than 10 years.
4. Family history of pre-eclampsia.
5. Previous history of pre-eclampsia.
6. Body mass index (BMI) of 30 kg/m2 or above at first
antenatal appointment.
7. Pre-existing vascular disease such as hypertension.
8. Pre-existing renal disease.
9. Multi-fetal pregnancy.
Risk factors on the rise
The pregnant population is changing, with an increase in obesity and age of conception meaning that the number of women that fall into the high or higher risk groups is increasing with a consequent rise in the number of pregnancies at risk of hypertensive complications. Over the last 10 years the number of women with a BMI of more than 30 has increased from 16% to 24%7 and the Centre for Maternal and Child Enquiries (CMACE) 2009 audit revealed that 5% of the pregnant population had a BMI more than 35 at any time during pregnancy, almost half of whom had a BMI of more than 40 (morbid obesity). Weight gain is well known to be associated with rising BP and is a major driver of hypertension.8 Furthermore, women are becoming pregnant at older ages: the conception rate for women aged 35 to 39 has almost doubled since 1990 and BP rises with age.
Best practice
The midwife’s role in the assessment and diagnosing hypertension is fundamental to the early detection and subsequent referral that will allow treatment to be implemented rapidly, potentially minimising the severity of the condition.
The midwife is in a prime position to identify those women who are more likely to develop gestational hypertension, and respond to detection of problems (see Figure 1).
Routine monitoring of blood pressure
Use of an accurate blood pressure monitoring device is fundamental to in making a correct diagnosis and thus determining potential referral (see Box 2). Both aneroid and digital sphygmomanometers are commonly used but they require regular calibration checks.
An additional issue for digital monitors is that, as a consequence of cardiovascular changes during pregnancy, many that are validated in the general population may not be accurate in pregnancy and pre-eclampsia. There are only a few monitors specifically validated for use in pregnancy and pre-eclampsia. These include; Omron-MIT Elite, Omron M7, Microlife WatchBPHome, and Microlife BP 3AC1-1 (see Resources section for more information).
How hypertension affects a pregnancy
Hypertensive disorders of pregnancy may impact the mother and fetus. A woman may develop severe hypertension (systolic blood pressure more than 160mmHg and/or diastolic more than 110mmHg), with risks of a stroke if this is unrecognised and untreated. The Confidential Enquiries into Maternal Death has repeatedly emphasised the need for prompt referral and treatment if a woman’s systolic blood pressure is more than 150mmHg, although the absolute risk of stroke is still low. A very small proportion of women may have an eclamptic fit without obvious hypertension or proteinuria preceding it. Women with
pre-eclampsia are also at risk of placental abruption and so any reports of abdominal pain, vaginal bleeding or reduced fetal movements should lead to immediate referral to a hospital unit.
Women with hypertensive disorders of pregnancy, particularly chronic hypertension and pre-eclampsia, are at greater risk of having a baby with fetal growth restriction. Growth scans are usually arranged for these women.
Women with hypertension and its complications (such as pre-eclampsia) may experience psychological stress and disruption of family life due to the need for extra hospital visits and potentially long stays as an inpatient. Community midwives can provide valuable support during pregnancy and after the birth for women at this time.
Management
Once diagnosed, treatment for hypertension during pregnancy aims to reduce maternal risks and achieve optimal perinatal survival. Blood pressures over 150/100mmHg typically require antihypertensive therapy; nifedipine, labetalol and methyldopa are most commonly used.
Women with chronic hypertension who are taking antihypertensive drugs prior to pregnancy should have their medication checked with their GP as soon as they know they’re pregnant. Angiotensin-converting-enzyme (ACE) inhibitors (usually ending in ‘pril’) and angiotensin receptor blockers (usually ending in ‘tan’) are not safe in pregnancy and diuretics (usually ending in ‘ide’) should also be stopped. Women who are at high risk of pre-eclampsia should be started on aspirin 75mg once daily to reduce their likelihood of developing the disease.6 In addition to antihypertensive therapy, more intensive monitoring is required with regular blood pressure checks, urine dipstick to detect the onset of pre-eclampsia, monitoring of fetal growth with ultrasound, cardiotocography (CTG) (in some cases), together with blood tests for detecting complications. Typically, a rising creatinine, urea and electrolytes (U&E), increasing alanine transaminase (ALT, checked on liver function tests) and falling platelet count (from full blood count) can detect complications and should prompt immediate referral if the woman is not already under hospital surveillance.
Postpartum support following pregnancy
The community midwife has a pivotal role to play in this period of transition to motherhood. It’s a time of emotional change and can be particularly difficult for women whose babies spend long periods in a neonatal unit with subsequent separation. Furthermore, new mothers with pregnancy induced hypertension may still require medication. Regular monitoring of BP should continue and liaison with the general practitioner is useful to ensure that the mother is on the right dose of antihypertensive medication.
Resources
British Hypertension Society – bhsoc.org
References
1. Duley L. The global impact of pre-eclampsia and eclampsia. Seminars in perinatology 2009;33(3):130-7.
2. Slattery MM, Geary M, Morrison JJ. Obstetric antecedents for preterm delivery. Journal of perinatal medicine 2008;36(4):306-9.
3. Rasmussen S, Irgens LM. The effects of smoking and hypertensive disorders on fetal growth. BMC pregnancy and childbirth 2006;6:16.
4. Altman D, Carroli G, Duley L, Farrell B, Moodley J, Neilson J, et al. Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial. Lancet 2002;359(9321):1877-90.
5. Health NCCfWsaCs. Hypertension in pregnancy: the management of hypertensive disorders during pregnancy. Royal College of Obstetricians and Gynaecologists, 2010.
6. NICE. Hypertension in adults: diagnosis and management. nice.org.uk/guidance/cg127 (accessed 19 February 2016).
7. Lifestyles Statistics Team. Statistics on Obesity, Physical Activity and Diet: England 2015. Health and Social Care Information Centre, 2015.
8. Modder J, Fitzsimons KJ on behalf of the Centre for Maternal and Child Enquiries and the Royal College of Obstetricians, Gynaecologists. CMACE/RCOG Joint Guideline: Management of Women with Obesity in Pregnancy Centre for Maternal and Child Enquiries. Royal College of Obstetricians and Gynaecologists, 2010.
9. Bramham K, Parnell B, Nelson-Piercy C, Seed PT, Poston L, Chappell LC. Chronic hypertension and pregnancy outcomes: systematic review and meta-analysis. British Medical Journal 2014;348:g2301.
10. NICE. Antenatal care for uncomplicated pregnancies. nice.org.uk/guidance/cg62 (accessed 19 February 2016).
11. Tranquilli AL, Dekker G, Magee L, Roberts J, Sibai BM, Steyn W, et al. The classification, diagnosis and management of the hypertensive disorders of pregnancy: A revised statement from the ISSHP. DOI: org/10.1016/j.preghy.2014.02.001 (accessed 26 February 2016).
