Because hypertension is one of the major complications linked to maternal death, there is a clear need for continued investigation. van Veen et al must be commended for their appropriate statistical analysis of the data on the subject. The transformations of the cerebral blood flow velocity are consistent with reliable standard methods. It was also relevant to measure the bilateral cerebral blood flow velocity to control for variation between the left and right hemispheres.

Although the statistical analysis methods of the authors are appropriate for the tests, the issues with the study are due to data collection. To access the effects of pregnancy on chronic conditions accurately, several measurements spanning the maximal allowable proportion of the pregnancy should have been taken. The patients underwent testing only for a single 7-minute period. The importance of taking into account the temporal factor is only further validated by the number of patients with gestational hypertension and chronic hypertension that developed the more severe preeclampsia during the course of the study. This limitation is noted briefly in the discussion but could have been addressed easily by increasing the number of data collection points as permitted by the duration of the pregnancy.

The second major methodologic shortcoming is that the researchers give little attention to a variety of additional confounders that complicate comparisons between groups. The hypertensive groups contained more patients with underlying diabetes mellitus than did the control group. This is problematic because type II diabetes mellitus has been shown to affect cerebral autoregulation even early in the disease, although there have been no comprehensive studies on the effects of gestational diabetes mellitus. The difference in the number of twin pregnancies between the groups further complicates analysis because differences in circulating angiogenic factors have been found between single and multiple fetus pregnancies. Little is known about how these factors affect the mother’s cerebral vasculature. Because the pathophysiologic condition of impaired cerebral autoregulation is largely undetermined, it is important that researchers implement stringent controls in studies that access its relationship to other conditions. These issues could have been avoided with stricter enrollment criteria that would have come at no additional cost to the researchers.

Although clinical studies that lack substantial funding are often subject to limitations, it is important to address these shortcomings. The authors should consider addressing these issues more completely in any future investigational studies on the topic.