Hypertensive disorders of pregnancy - Q & A with Dr Amanda Henry
Dr Amanda Henry, Senior Research Fellow at The George Institute for Global Health's Women's Health Program answers questions about the long term health implications of hypertensive disorders of pregnancy.
What are hypertensive disorders of pregnancy (HDP)?
There are several pregnancy conditions where the major clinical feature is high blood pressure (hypertension), and these are together known as hypertensive disorders of pregnancy (HDP for short).
The three main HDP are: firstly, preeclampsia, which is a multi-system disorder unique to pregnancy whose effects can include kidney injury, liver injury and clotting problems for the mother, and/or growth problems for the baby. Secondly, gestational hypertension, which is high blood pressure only, without the multisystem features of preeclampsia, and thirdly, chronic hypertension in pregnancy, where women come into pregnancy already having high blood pressure (they may also get preeclampsia in addition to their chronic hypertension).
HDP occurs globally in 5-10% of pregnancies, so in Australia alone that’s about 30,000 women a year. It’s in the top 5 causes of maternal death and severe disability worldwide, and also a major cause of preterm birth and stillbirth.
Who is most at risk?
Any pregnant woman can get HDP, however the following women are more likely to get HDP:
- Older mothers, first time mothers, those with high BMI (i.e. overweight or obese at the start of pregnancy), those with multiple pregnancy (twins or more), those who have a history of HDP in a previous pregnancy, and those with a family history.
- Women are also more likely to get preeclampsia specifically if they have chronic high blood pressure (about 1 in 4 will get preeclampsia in addition to their chronic hypertension), or have a predisposing medical condition such as diabetes, pre-existing kidney disease, or connective tissue disease (20-50% of these women will develop preeclampsia). Preeclampsia also seems to be more common in certain ethnicities - Caucasian, African American, and First Peoples, with lower rates in women of Asian background.
Why is it important to raise awareness of this condition and the cardiovascular health of women after they’ve had this condition? Don’t the effects of HDP end after the pregnancy?
Although most women’s blood pressure will return to normal within a few months after an HDP-affected pregnancy, and signs of any organ damage (e.g. kidney injury from preeclampsia) will also resolve, unfortunately there are long-term increased health risks after having HDP. It has been well known for many years that chronic hypertension is a risk factor for cardiovascular disease, however it is now also very clear from population studies that the risk of cardiovascular disease (CVD) is also increased after both preeclampsia and gestational hypertension, not just for women with chronic hypertension.
The risk of heart attack, stroke, and cardiovascular death, are all approximately doubled after HDP. Women are also at increased risk of Type 2 diabetes (even if they didn’t have diabetes during pregnancy), and long-term kidney disease. These risks appear to be present within the first 5-10 years after an HDP-affected pregnancy, and to continue for lifetime. HDP also appears to be an independent risk factor for CVD, as whenever studies have been able to adjust for other CVD risk factors (e.g. smoking, overweight/obesity) the effect of having HDP persists.
Given that cardiovascular disease is the leading cause of death for women globally, a doubling of a woman’s future risk of CVD is of major public health importance.
How can women with this risk manage this condition/reduce the risk? What are your top 3 tips?
Unfortunately we don’t yet have much evidence focussed on women after HDP when it comes to reducing cardiovascular disease and diabetes risk. Our group has just published a review of intervention studies in the first 10 years after an HDP-affected pregnancy, which suggests lifestyle behaviour change measures show promise, but the data is not definitive yet. We are currently running the BP2 (Blood Pressure Postpartum) randomised trial in five Sydney hospitals, studying three different methods of follow-up, risk factor assessment and lifestyle behaviour change in the first 12 months after HDP. In collaboration with our partners at Shenzhen Maternity and Child Hospital, a similar study will also shortly commence in China.
Until we have these results, the advice that I would give (in line with international guidelines) is;
- Follow-up with your GP after an HDP affected pregnancy to ensure your blood pressure has returned to normal (and if not, to have appropriate tests/assessment by a specialist).
- Have your heart disease risk factors assessed within the first year after pregnancy, (then at least every 5 years after that), and manage any that are found.
- Maintain a healthy lifestyle: regular physical activity, healthy diet, don’t smoke, and maintain a healthy weight.
What does your most recent publication aim to find out about HDP?
We believe part of the issue with identifying and managing long-term health after HDP is that neither women nor their healthcare providers have a high level of understanding of risks after HDP. Our publication reviews the international evidence around women’s knowledge of health after HDP (and what are nominated as barriers and enablers to both their knowledge and acting on that knowledge), and also the knowledge of healthcare providers.
Most reviewed studies found that women had low levels of knowledge about CVD risk after HDP, and where they did have knowledge they had often sourced it themselves (e.g. the internet) rather than being informed by their healthcare provider. Several studies also found limited knowledge among healthcare providers. Obstetricians as a group seemed to have a reasonable level of knowledge, but often didn’t communicate it to either other healthcare provider colleagues such as GPs, or to the women themselves.
We have recently completed our own Australian survey of healthcare providers and women about health after HDP, and with the review findings and our own survey data are now moving to design appropriate education and support packages for women after HDP, and for primary healthcare providers.
