Higher BP in First Trimester May Increase Preeclampsia Risk

Jennifer Garcia

February 10, 2014

Elevations in blood pressure in the first trimester of pregnancy, even those below the cutoff for overt hypertension, may increase the risk for preeclampsia among women receiving aspirin prophylaxis, according to a new study published in the March issue of Obstetrics & Gynecology.

Dana M. Block-Abraham, DO, from the University of Maryland School of Medicine, Baltimore, and colleagues enrolled 614 women between 2007 and 2010 in the study. The women were 9 to 14 weeks pregnant and receiving aspirin prophylaxis (81 mg/day) because they were at high risk for preeclampsia.

The researchers found that 9.6% (59) of women receiving aspirin prophylaxis developed preeclampsia and that these women had a higher median BP during their first trimester compared with women who did not develop preeclampsia (127/75 mm Hg vs 117/68 mm Hg, respectively).

The researchers measured BP at the time of enrollment and classified it according to Joint National Committee on Hypertension 7 guidelines as follows:

  • normal: systolic BP is less than 120 mm Hg, diastolic BP is less than 80 mm Hg;

  • prehypertension: systolic BP is 120 to 129 mm Hg, diastolic BP is 80 to 89 mm Hg;

  • hypertension (stage 1): systolic BP is 140 to 159 mm Hg, diastolic BP is 90 to 99 mm Hg, or both; and

  • hypertension (stage 2): systolic BP is 160 mm Hg or higher, diastolic BP is 100 mm Hg or higher, or both.

Women who developed elevations in BP during their first trimester and who were classified as having either prehypertension or hypertension according to the Joint National Committee on Hypertension 7 guidelines had a 2-fold increase in their risk for preeclampsia. Normal BP during the first trimester of pregnancy, in contrast, was associated with a 56% reduction in the risk for preeclampsia.

The authors used these findings to create receiver operating characteristic curves to determine cutoff values for systolic and diastolic BP with greater sensitivity and specificity for the development of preeclampsia. They found that a systolic BP of more than 122 mm Hg was 66% sensitive and 70% specific for the development of preeclampsia, and a diastolic BP of more than 72 mm Hg was 64% sensitive and 71% specific.

The researchers also found that the presence of diabetes and a prior history of preeclampsia were independent contributors to the development of preeclampsia during the studied pregnancy. The women who developed preeclampsia were also more likely to have a body mass index in the obese range (30 kg/m2 or higher).

The researchers acknowledge study limitations such as the fact that adherence to aspirin therapy was not verified and timing of administration was not standardized. The majority of patients were black, and results may not be applicable to all patient populations.

Further research will be needed to better understand the relationship between first trimester BP, preeclampsia, and aspirin prophylaxis, the authors note. "The fact that normal first-trimester BP (less than 120/80 mm Hg) was associated with a decreased preeclampsia risk in women on aspirin prophylaxis highlights the importance of BP in preeclampsia development," write Dr. Block-Abraham and colleagues. "Extrapolating from the internal medicine literature, and supported by our study findings, further research is warranted to clarify the role of first-trimester antihypertensive therapy at lower BP thresholds."

Funding for this study was provided by a grant from Diagnostic Technologies Limited. The authors have disclosed no relevant financial relationships.

Obstet Gynecol. 2014;123:611-617.

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