Open Access
Feature Article

Chronic hypertension and pregnancy – emphasising longitudinal care to improve maternal and fetal health

Open Access
Feature Article

Chronic hypertension and pregnancy – emphasising longitudinal care to improve maternal and fetal health

CATHERINE BRUMBY, LAWRENCE P. MCMAHON

Figures

© katarzynabialasiewicz/ istockphoto.com models used for illustrative purposes only
© katarzynabialasiewicz/ istockphoto.com models used for illustrative purposes only
Dr Brumby is a Nephrologist at Eastern Health, Melbourne; and Adjunct Senior Lecturer, Eastern Health Clinical School, Monash University, Melbourne. Professor McMahon is a Nephrologist and Obstetric Medicine Physician at Eastern Health; and Professor at Eastern Health Clinical School, Monash University, Melbourne, Vic.

Abstract

Pregnant women with chronic hypertension are at high risk of adverse outcomes, many of which are potentially preventable. GPs play a crucial role in ensuring women with chronic hypertension are appropriately managed before, during and after pregnancy to minimise complications to mother and baby.

Key Points

  • Common risk factors for chronic hypertension in young women include obesity, family history, kidney disease and a past history of hypertension in pregnancy or pre-eclampsia.
  • Chronic hypertension affects around 0.6 to 3% of pregnancies in Australia; a quarter of these women will experience superimposed pre-eclampsia.
  • Chronic maternal hypertension is defined as either a previous documented history of or treatment for hypertension outside pregnancy or, alternatively, a blood pressure of 140/90mmHg or higher on at least two occasions before 20 weeks’ gestation.
  • Screening for secondary causes of hypertension is indicated in women of childbearing age with chronic hypertension. In pregnancy, screening can usually be deferred until postpartum.
  • Blood pressure targets in pregnancy are now similar to those in the general population, and home blood pressure monitoring can be a valuable tool to enhance control and improve patient engagement.
  • Methyldopa and labetalol continue to be the cornerstones of safe and effective blood pressure management in pregnancy.

Chronic maternal hypertension affects about 0.6 to 3% of pregnancies in Australia, although this is likely an underestimate.1,2 Globally, the incidence of chronic hypertension in pregnant women is rising, with increasing maternal age at delivery and obesity rates likely contributing factors. Chronic maternal hypertension is a risk factor for significant maternal and perinatal morbidity, including preterm birth, pre-eclampsia, caesarean section, low birthweight and perinatal death. The incidence of superimposed pre-eclampsia in particular is 25.9% compared with significantly lower rates (3 to 5%) in normotensive women.3

For some women, the diagnosis of chronic hypertension is made preconception. This allows for timely pre-pregnancy counselling and planning to improve antenatal care and optimise outcomes. However, many women are initially identified as hypertensive in the first half of pregnancy (before 20 weeks’ gestation), highlighting the importance of blood pressure screening in early pregnancy consultations. Essential hypertension remains the most common cause of hypertension in younger women. By definition, essential hypertension requires investigation and exclusion of secondary causes that may be done preconception but, in most cases, can be safely delayed until postpartum. Secondary causes are disproportionately represented in women of childbearing age and are estimated to account for more than 15% of cases.4 

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Most preconception, first-trimester and postpartum healthcare interactions in women with chronic hypertension who are pregnant or planning pregnancy are with their GP. Thus, GPs play a crucial role in longitudinal care and ensuring that opportunities for improving pregnancy outcomes and long-term health in young mothers are not missed. This review highlights important issues and provides guidance for GPs on optimal management of this important group of patients.   

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Chronic maternal hypertension and adverse pregnancy outcomes

Pregnancies affected by chronic maternal hypertension have increased rates of maternal and fetal morbidity. Although much of the morbidity such as preterm birth is attributable to high rates of superimposed pre-eclampsia, other adverse outcomes, such as placental abruption or low birthweight, appear to be independently linked to chronic maternal hypertension.5 Chronic hypertension often also coexists with other common comorbid conditions or lifestyle risk factors in the pregnant population including diabetes, obesity, kidney disease and smoking. These additional factors may further increase risk of pregnancy complications. Importantly, many of these factors are potentially modifiable, and so pregnancy-related complications can be minimised with good preconception management of chronic disease, together with optimisation of lifestyle factors. 

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