The document states, in other words, that to establish preeclampsia, equal weight should be given to any of these so-called severe features – even in the absence of proteinuria – when they occur along with new-onset hypertension at 20 weeks’ gestation or beyond. (The blood pressure criteria stipulate hypertension as a systolic blood pressure of 140 mm Hg or higher and a diastolic of 90 mm Hg or higher, taken on at least two occasions 4 hours apart.)
This new approach to diagnosing preeclampsia is a major change. It reflects what the ACOG document rightly calls a "minimal relationship" between the quantity of urinary protein and maternal and fetal outcomes in preeclampsia, as well as the fact that preeclampsia may quickly evolve. We need these broader criteria and lower thresholds so that we will not miss patients who might present atypically, with proteinuria not yet a significant finding, but with disease quickly developing.
Another helpful change is the removal of significant fetal growth restriction (less than the fifth percentile) as a diagnostic feature for traditionally coined "severe preeclampsia." Fetal growth restriction is not included in ACOG’s recommended list of severe features of preeclampsia. This is a helpful clarification that should prevent potentially unnecessary deliveries. The problems of fetal growth restriction (FGR) and preeclampsia should be considered and managed separately, with the option of expectant management considered with respect to each entity alone, as opposed to the finding of FGR driving a diagnosis of severe preeclampsia and thus delivery within 48 hours.
Where evidence is strongest
ACOG’s report contains 60 distinct recommendations covering hypertensive disorders in pregnancy, but only 6 of these recommendations are graded as both "strong" and based on "high-quality" evidence. (A "strong" recommendation is one that the task force considered so well supported by the literature that it is applicable to "virtually all patients.")
The remaining recommendations are either graded as "qualified" or are based on evidence that is rated as "very low," "low," or "moderate," or some combination of the "qualified" grade and a quality-of-evidence ranking below "high."
The task force utilized a strategy developed by the Grading of Recommendations Assessment, Development and Evaluation Working Group that rates the quality of evidence based largely on what’s called "confidence in estimates of effect." Under this approach, randomized, controlled trials are important but may still be considered flawed and observational studies are usually but not necessarily classified as low quality.
The small number of strong, high-quality recommendations in the ACOG report reflects the fact that, despite advances in our understanding of preeclampsia, there are many areas in which we lack good evidence from randomized, controlled trials. Importantly, the task force emphasizes that it offers recommendations and not prescriptions, and that sound clinical judgment remains a key part of patient management.
The six strong recommendations in the report that are based on high-quality evidence are as follows:
• The administration of vitamin C or vitamin E to prevent preeclampsia is not recommended.
• Women with severe preeclampsia who are being expectantly managed at 34 weeks’ or less of gestation should receive corticosteroids for the benefit of accelerating fetal lung maturation.
• Women who have chronic hypertension with superimposed preeclampsia and are being expectantly managed at 34 weeks’ or less of gestation also should have corticosteroids administered for the purpose of accelerating fetal lung maturation.
• For women with eclampsia, the administration of parenteral magnesium sulfate is recommended.
• For women with severe preeclampsia, the administration of intrapartum-postpartum magnesium sulfate to prevent eclampsia is recommended.
• For women with HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome who are before the gestational age of fetal viability, delivery should be undertaken shortly after initial maternal stabilization.
My take
Contrary to former recommendations, the task force’s new recommendations suggest that use of magnesium sulfate for preeclampsia without severe features (formerly called "mild preeclampsia") may not be needed. Although magnesium sulfate may not be warranted in every case, patients can progress so rapidly from having no severe symptoms to developing severe symptoms that it is difficult if not impossible to parse out who would or would not benefit from treatment. If we try to do so, we run the great risk of not providing the necessary medication to our patients, thereby increasing the chances of maternal morbidity and mortality.
In our institution, we continue to use magnesium sulfate intrapartum and post partum for every patient with a diagnosis of preeclampsia, whether or not she has severe features. Without high-quality evidence to the contrary, I do not believe that we should alter the former recommendation that magnesium sulfate be used in all cases of preeclampsia. We administer the agent for 24 hours post partum because studies looking at a 48-hour window have shown that most patients who have an eclamptic seizure within 48 hours after delivery will actually experience it within the first 24 hours.