GRAPEVINE, TEX. – Blood pressure categories created by the American College of Cardiology (ACC) and American Heart Association (AHA) in 2017 identify patients with increased risk of preeclampsia, preterm birth, and perinatal death when applied to the first 20 weeks of pregnancy, according to a retrospective study presented at the meeting sponsored by the Society for Maternal-Fetal Medicine.
Dr. Martha Tesfalul
The absolute risk increases are small, and it is unknown whether treating these patients differently would be beneficial, said study author Martha Tesfalul, MD, maternal-fetal medicine clinical fellow at University of California, San Francisco. Nevertheless, , Dr. Tesfalul said.
Cutoffs with unclear implications
The ACC/AHA in November 2017 reclassified blood pressure in nonpregnant adults, but “implications of these categories in pregnancy are still unclear,” Dr. Tesfalul and colleagues said. Under the guidelines, normal blood pressure is systolic blood pressure less than 120 mm Hg and diastolic blood pressure less than 80 mm Hg. Elevated blood pressure is defined as systolic blood pressure between 120 and 129 mm Hg and diastolic blood pressure less than 80 mm Hg. Stage 1 hypertension is systolic blood pressure between 130 and 139 mm Hg or diastolic blood pressure between 80 and 89 mm Hg. And stage 2 hypertension is systolic blood pressure of at least 140 mm Hg or diastolic blood pressure of at least 90 mm Hg.
For the present analysis, the researchers retrospectively compared obstetric and perinatal outcomes for approximately 6,000 pregnancies at an academic center for which they had at least one blood pressure measurement prior to 20 weeks. The highest measurement was used to identify women with normal blood pressure, elevated blood pressure, or stage 1 hypertension according to the 2017 thresholds.
The researchers included singleton pregnancies with delivery between January 2014 and October 2017. They excluded patients with a prior diagnosis of chronic hypertension, autoimmune or chronic renal disease, or fetal anomalies. They examined rates of gestational hypertension, preeclampsia, preterm birth, neonatal intensive care admission, and perinatal death.
Adjusted relative risks
Dr. Tesfalul and colleagues identified about 3,500 pregnancies with normal blood pressure, more than 1,300 pregnancies with elevated blood pressure, and nearly 1,100 pregnancies with stage 1 hypertension.
After adjusting for relevant covariates – maternal age, nulliparity, race, body mass index, in vitro fertilization, tobacco use, pregestational diabetes, and aspirin use – elevated blood pressure and stage 1 hypertension were associated with a higher risk of preeclampsia and severe preeclampsia, relative to normal blood pressure. The proportion of patients with preeclampsia was 5.7% in the normal blood pressure group, 11.7% in the elevated blood pressure group (adjusted relative risk, 1.8), and 15% in the stage 1 hypertension group (adjusted RR, 2.1). The proportion with preeclampsia with severe features was 3.1% in the normal blood pressure group, 5.7% in the elevated blood pressure group (adjusted RR, 1.6), and 6.8% in the stage 1 hypertension group (adjusted RR, 1.8).
In addition, stage 1 hypertension, compared with normal blood pressure, was associated with increased odds of preterm birth at less than 37 weeks (7.9% vs. 5.1%; adjusted RR, 1.4) and perinatal death (0.7% vs. 0.4%; adjusted RR, 2.8).
“Patients with elevated blood pressure and stage 1 hypertension prior to 20 weeks are at increased risk of adverse outcomes,” the authors concluded. “Further research [is] needed to determine optimal care of patients with elevated blood pressure and stage 1 hypertension in pregnancy.”
Dr. Tesfalul receives support from the Foundation for SMFM.
SOURCE: Tesfalul M et al. Am J Obstet Gynecol. 2020 Jan;222(1):S92-3, Abstract 119.