Hypertensive Disorders in Pregnancy - 1
Earlier this week, I was asked to speak at a meeting that focused on the high fetal and infant mortality rates in one of our state perinatal regions. The goal was to identify risk factors and propose interventions that might begin to lower those rates which happen to be among the worst in the U.S. The postnatal factors that were most frequently associated with deaths of infants after delivery were found to be ‘sudden infant death syndrome (SIDS)’ and ‘unsafe sleeping practices.’ The tragedy is that many of these deaths are preventable and I will address those issues in a future post. The prenatal factors that were most strongly correlated with poor outcomes are pregnancy-induced hypertensive disorders and these were the subject of my discussion. Since summer seems to bring out the worst of these problems in the southeast, I thought it would be a good time to present a series to our readers on this topic.
Hypertensive disorders in pregnancy complicate 12-22% of all pregnancies. They are the second leading cause of maternal mortality, accounting for 17.6% of pregnancy-related deaths in the U.S. Worldwide, it is estimated that 75,000 maternal deaths are related to these conditions. They are also a leading factor contributing to premature deliveries and, in the U.S.; this translates to an average cost of about $50,000 per infant! About 70% of hypertensive complications in pregnancy are classified as ‘pregnancy-induced hypertensive’ disorders, sometimes referred to as ‘gestational hypertension’, but better categorized as a spectrum of conditions we lump under preeclampsia. About 30% of the complications are related to chronic hypertension with or without superimposed preeclampsia.
The definition we use for hypertension is a diastolic blood pressure greater than or equal 90mmHg or a systolic pressure greater than or equal 140mmHg and we generally do not label someone as ‘hypertensive’ unless the blood pressure (BP) is elevated on at least two occasions 6 or more hours apart. Of course, there are times when the BP is so abnormal that we break this rule! Chronic hypertension during pregnancy is usually defined as persistent hypertension from any cause that is present before 20 weeks gestation. Pregnancy-induced hypertension (PIH) is defined as the onset of hypertension after 20 weeks in a woman with previously normal BP. Occasionally, hypertension is truly PIH and found before 20 weeks and when this occurs it is often the result of abnormal placental tissues associated with either a ‘molar’ pregnancy, a chromosomally abnormal baby, severe isoimmunization, or congenital infection. And, when a woman shows up for her initial prenatal care for the first time after 20 weeks and is hypertensive, it can sometimes be difficult (at first) to decide whether this is PIH or simply chronic hypertension. Okay, now that we are clear on all that, in the next post, I will begin to address the diagnosis of preeclampsia during pregnancy…