Take a history and assess if investigation for secondary causes is required

• CKS has based these recommendations on accepted clinical practice.

Dipstick urine for proteinuria

• Proteinuria in women with chronic hypertension may be:
• Due to underlying renal disease.
• Due to the development of pre-eclampsia if it is new and occurs after 20 weeks' gestation.
• The National Institute for Health and Clinical Excellence (NICE) recommends the use of automated dipstick testing in secondary care. Evidence from a meta analysis of six trials and a prospective study showed that visual dipstick analysis of urine with a 1+ threshold is not accurate at detecting clinically significant proteinuria. Its use in clinical decision making is therefore limited. Accuracy is improved by using an automated dipstick device. Primary care clinicians should use automated dipsticks if they have access to them.

Assessing for symptoms of pre-eclampsia

• This recommendation is based on expert advice [National Collaborating Centre for Women's and Children's Health, 2010] and three narrative reviews [Sadovsky, 2002; Duley et al, 2006; Young et al, 2010]. Women with chronic hypertension are at increased risk of pre-eclampsia [National Collaborating Centre for Women's and Children's Health, 2010].

Low salt diet

• On the basis of expert opinion, the National Institute for Health and Clinical Excellence (NICE) recommends that pregnant women with chronic hypertension should follow the same general advice in relation to dietary salt intake as women with hypertension who are not pregnant [National Collaborating Centre for Women's and Children's Health, 2010]. This is because the pathogenesis is the same and reducing the intake of salt can lower blood pressure.

Bed rest

• NICE reviewed the literature on the benefits of bed rest during pregnancy in women with chronic hypertension [National Collaborating Centre for Women's and Children's Health, 2010]. NICE reviewed a randomized controlled trial (RCT) done in 218 women in Zimbabwe. This study examined the effectiveness of hospital bed rest compared with normal activities at home on the risk of developing severe hypertension in women with chronic hypertension or gestational hypertension [National Collaborating Centre for Women's and Children's Health, 2010]. Thirty-three women in the chronic hypertension group were randomized to normal activities at home (18 women) or hospital bed rest (15 women). There was no statistically significant difference between the two groups with regard to the development of severe hypertension, proteinuria, or severe proteinuria. NICE concluded that there is no evidence that bed rest is beneficial. There is also concern that prolonged bed rest may increase the risk of venous thromboembolism.

Frequency of monitoring of blood pressure

• There is no evidence on which to base recommendations regarding frequency of antenatal contacts for women with chronic hypertension. The view of NICE, however, is that the routine schedule for antenatal care monitoring of blood pressure is inadequate for pregnant women with chronic hypertension [National Collaborating Centre for Women's and Children's Health, 2010].

Target blood pressure

• NICE reviewed the literature and found that [National Collaborating Centre for Women's and Children's Health, 2010]:
• There is evidence from two good-quality studies that there is less risk of severe hypertension with 'tight' blood pressure control but no other differences in maternal or perinatal outcomes, including fetal growth.
• A meta-regression of RCTs found that the more blood pressure is reduced in pregnant women with hypertension, the more the birthweight of their infants is reduced. This meta-regression included women taking methyldopa, acebutolol, atenolol, labetalol, metoprolol, oxprenolol, pindolol, propranolol, bendroflumethiazide, chlorothiazide, hydrochlorothiazide, ketanserin, hydralazine, isradipine, nicardipine, nifedipine, verapamil, and clonidine.
• On the basis of these studies, NICE recommends that:
• Treatment should aim to lower blood pressure from the moderate or severe range, but excessive reduction of blood pressure should be avoided as this may affect fetal growth.
• Women with target-organ damage would need a lower blood pressure target than women without target-organ damage.

Advising about symptoms of pre-eclampsia

• This recommendation is based on expert advice from NICE and three narrative reviews [Sadovsky, 2002; Duley et al, 2006; Young et al, 2010]. Women with chronic hypertension are at increased risk of pre-eclampsia [National Collaborating Centre for Women's and Children's Health, 2010].
• A key recommendation from the 1998 Confidential Enquiry into Maternal Deaths that is accepted good clinical practice is that all women should receive antenatal education so that they are aware of the symptoms associated with pre-eclampsia (such as headache or epigastric pain), its importance, and the need to obtain medical advice [DH, 1998].

Aspirin to prevent pre-eclampsia

• NICE concluded that there is evidence from a meta-analysis that aspirin is effective in reducing the risk of pre-eclampsia, including in women who have chronic hypertension [National Collaborating Centre for Women's and Children's Health, 2010].
• Some CKS expert reviewers warned against prescribing aspirin to women with uncontrolled blood pressure. CKS recommends that in such women, it is best to seek specialist advice about whether or not to prescribe aspirin.

Stopping angiotensin-converting enzyme (ACE) inhibitors or angiotensin-II receptor antagonists (AIIRA)

• There is limited evidence regarding the use of ACE inhibitors or AIIRAs during pregnancy. Studies suggest that ACE inhibitors are associated with congenital malformations, intrauterine growth retardation, and premature delivery, and that AIIRAs are associated with congenital malformations.
• NICE states that there is sufficient concern, despite the relatively poor quality of the studies, to recommend avoiding ACE inhibitors and AIIRAs during pregnancy [National Collaborating Centre for Women's and Children's Health, 2010].

Chlorothiazide is also possibly teratogenic but is not prescribable in the UK

• NICE noted a possible association with congenital abnormalities, neonatal thrombocytopenia, neonatal hypoglycaemia and hypovolaemia, and possible maternal electrolyte imbalance [National Collaborating Centre for Women's and Children's Health, 2010].

Other antihypertensive drugs during pregnancy

• NICE reviewed studies of other antihypertensive drugs and found:
• No obvious association with congenital abnormalities for the following drugs: methyldopa, labetalol, atenolol, metoprolol, oxprenolol, pindolol, prazosin, nifedipine, verapamil, bendroflumethiazide, furosemide, and hydralazine. No or very little information about other antihypertensive drugs is available.
• Antihypertensives reduce the risk of severe hypertension but not of proteinuria.
• From the limited available evidence, it is not possible to determine the best antihypertensive treatment for pregnant women with chronic hypertension.

Referral to a specialist

• NICE states that the evidence from trials on the treatment of blood pressure does not make it possible to determine the best antihypertensive treatment for a pregnant woman [National Collaborating Centre for Women's and Children's Health, 2010]. CKS recommends seeking specialist advice before starting treatment. If the woman's blood pressure is normal, then it should be checked regularly.