Pre-Eclampsia and Maternal Cardiovascular Function: Insights Into Pathophysiology and Care (Scientific Impact Paper No. 79).

Pre-eclampsia is a pregnancy complication that involves the development of high blood pressure in a pregnant woman and other features such as protein in the woman's urine, kidney or liver problems, or poorer growth for the baby. It can also have long-term health impacts for the mother after pregnancy. Pre-eclampsia typically occurs after 20 completed weeks of pregnancy (either mid-pregnancy known as 'early onset pre-eclampsia' or, more commonly, later in pregnancy, at or after 34 weeks, known as 'late onset' pre-eclampsia). Different blood pressure medications can be used to treat this condition, but not all women respond in the same way to the same medication. This is probably due to variables in the function of the maternal heart and blood vessels. Over the past 20 years, technological developments have meant it is now possible to measure important individual aspects of maternal cardiovascular function, using simple non-invasive tests. These tests can establish whether the mother's heart and circulatory system have any unusual features that may place her at higher risk of complications. They can also be used to monitor whether the mother's health and circulatory system is adapting in the right way to the pregnancy. For example, it is now possible to measure cardiac output (volume of blood pumped out by the heart) and vascular resistance (the physical resistance to the flow of blood), as well as the mother's blood pressure. It is also possible to monitor if and how changes in the above follow the patterns of change that are usually seen during pregnancy. Testing, and repeat testing as necessary, can identify individual measurements, or patterns of measurements, of concern and can identify whether the mother's heart and blood flow are adapting to the pregnancy in the typical and expected way. Studies in these areas have shown two distinct patterns of abnormal measurements of blood circulation and heart health in the pregnant woman that can occur with pre-eclampsia. Some changes and abnormalities can be detected before the symptoms of pre-eclampsia become obvious. Some features associated with pre-eclampsia can also be detected early in pregnancy or even before pregnancy. For example, we understand that some pregnant women who have a lower volume of blood being pumped out of their hearts per minute (low cardiac output), are more at risk of being affected by pre-eclampsia earlier in pregnancy, and more likely to have a baby with a low birth weight. Women that develop pre-eclampsia later in pregnancy typically have more circulating blood and babies of normal or larger size. The distinct measurable features of maternal heart health and blood flow can be used to identify those women at risk of developing pre-eclampsia at an early stage. Recognising the features of maternal heart health and the patterns of blood flow associated with pre-eclampsia provides an opportunity to individualise treatment plans for pregnant women, such as a personalised plan of monitoring and review, and using the most appropriate drugs that are tailored to address specific difficulties and likely to be most effective in restoring balance to the circulatory system of that individual. Early recognition, before the onset of symptoms, also allows timely reviews, and appropriate treatment to be started sooner. This, in turn, can lower the incidence of serious manifestations of pre-eclampsia for the mother, such as the development of seizures or a stroke. There is clear evidence that the management of pre-eclampsia can be improved by more detailed cardiovascular evaluation and tailored monitoring. The drugs that lower blood pressure work in different ways and the opportunity exists to target therapy to the underlying problem, however at the time of writing, many of the non-invasive tests and assessments able to identify women at risk of pre-eclampsia are typically only being used in a research setting. Routine clinical use of the available tests, and the establishment of clear care pathways and defined parameters for risk assessment based on those maternal heart and circulation test results, would allow targeted treatment and assist in preventing avoidable harm.