The hypertensive complications of pregnancy are divided into four distinct classifications: Preeclampsia/eclampsia, Chronic hypertension, preeclampsia superimposed on chronic hypertension, and gestational hypertension. Many people are perplexed by the term "superimposed preeclampsia" which is preeclampsia complicating hypertension of another cause, most commonly chronic or "essential" hypertension. However women with hypertension associated with diabetes, pre-existing autoimmune disorders like lupus erythematous, and chronic kidney disease also have an increased chance of developing superimposed preeclampsia.
Women may know when entering pregnancy that they are chronic hypertensives. But chronic hypertension can also be unmasked when a woman develops high pressures (either of 140/90 mm Hg) before 20 weeks gestation, even if she had normal blood pressure before pregnancy. Whatever are the aberrations in the placenta that cause preeclampsia, women with chronic hypertension, of any cause, are more susceptible and more likely to develop preeclampsia.
All pregnant women have what is called an enhanced inflammatory state and some researchers suggest that further exaggeration of this state leads to preeclampsia. In a sense, some women enter pregnancy with the inflammatory glass half-full of water, and then pregnancy adds to it. At some point, the cup will overflow. Autoimmune conditions, like some forms of diabetes and kidney disease, are also associated with increased inflammation, and this may be why they are more prone to preeclampsia.
Diagnosing chronic hypertensives with preeclampsia can be tricky, as the normal markers of preeclampsia (blood pressure elevations of 140/90) are likely already present. Also some chronic hypertensives have early kidney changes and may spill some extra protein later in pregnancy when all pregnant women excrete more protein. Doctors are also extra cautious with chronic hypertensives because superimposed preeclampsia can be severe or "fulminating", which means that it gets bad, rapidly. Women with superimposed preeclampsia are delivered earlier in pregnancy. They are more likely to need Caesarean section deliveries because their condition develops too quickly to allow for induction, and their infants are more likely to need NICU time.
If you have a history of chronic conditions, if you developed hypertension before 20 weeks gestation, or it took longer than 6-8 weeks to resolve after delivery, your later pregnancies are at higher risk for superimposed preeclampsia. A consult with a maternal-fetal medicine specialist before conception will allow you to make a plan for how any subsequent pregnancies might be managed. Consider asking these questions:
- Do I need to change medications?
- Should I undertake a weight-loss program?
- When should I call about a change in symptoms?
- At what point in symptom progression would I be admitted for observation?
Among the varying searches for a way to prevent preeclampsia are recent research efforts focusing on ways to lower inflammation, but no effective therapies have been identified yet. The Preeclampsia Foundation funds research investigating potential mechanisms and therapies each year, with Vision Grants awarded at the Saving Grace Gala.