Hauspurg A, Parry S, Mercer BM, et al. Blood pressure trajectory and category and risk of hypertensive disorders of pregnancy in nulliparous women. Am J Obstet Gynecol. 2019. pii: S0002-9378(19)30807-5. doi: 10.1016/j.ajog.2019.06.031.
Hauspurg and colleagues set out to determine whether redefined BP category (normal, < 120/80 mm Hg) and trajectory (a difference of ≥ 5 mm Hg systolic, diastolic, or mean arterial pressure between the first and second prenatal visit) helps to identify women at increased risk for developing hypertensive disorders of pregnancy or preeclampsia.
With respect to the former variable, such an association was demonstrated in the first National Institutes of Health–funded preeclampsia prevention trial published in 1993, which used low-dose aspirin.1 In that trial, low-dose aspirin was not found to be effective in preventing preeclampsia in young, healthy nulliparous women. Interestingly, the 2 factors most associated with developing preeclampsia were an initial systolic BP of 120 to 134 mm Hg and an initial weight of >60 kg. For most clinicians, these findings would not be helpful in trying to better identify a high-risk group.
Details of the study
The idea of BP “trajectory” is interesting in the Hauspurg and colleagues’ study. The authors analyzed data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b), a prospective cohort study, and included a very large population of almost 9,000 women in the analysis. Participants were classified according to their BP measurement at the first study visit, with BP categories based on updated American College of Cardiology/American Heart Association guidelines. The primary outcome was the risk of hypertensive disorders of pregnancy, including gestational hypertension and preeclampsia.
The data analysis found that elevated BP was associated with an adjusted risk ratio (aRR) of 1.54 (95% confidence interval [CI], 1.18–2.02). Stage 1 hypertension was associated with an aRR of 2.16 (95% CI, 1.31–3.57). Compared with women whose BP had a downward systolic trajectory, women with normal BP and an upward systolic trajectory had a 41% increased risk of any hypertensive disorder of pregnancy (aRR, 1.41; 95% CI, 1.20–1.65).
Study strengths and limitations
While the large study population is a strength of this study, there are a number of limitations, such as the use of BP measurements during pregnancy only, without having pre-pregnancy measurements available. Further, a single BP measurement during each visit is also a drawback, although the standardized measurement by study staff is a strength.
Anticlimactic conclusions. The conclusions of the study, however, are either not surprising, not clinically meaningful, or of little value to clinicians at present, at least with respect to patient management.
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