ACC/AHA guidelines for identifying gestational hypertension

A blood pressure of 130/ ≥ 80 mm Hg for identifying hypertension in adults was recommended by the American College of Cardiology (ACC) and American Heart Association (AHA) in 2017-but that applies only to those who are not pregnant. A new study looks at whether that yardstick also could be used to detect gestational hypertension. 

A statement from the American College of Obstetricians and Gynecologists (ACOG), issued in 2013, defines hypertension as a systolic blood pressure (SBP) ≥ 140 mm Hg or a diastolic blood pressure (DPB) ≥ 90 mm Hg.

Published in the Journal of the American Heart Association, the new analysis was done by Chinese researchers using a birth cohort of 16,345 women with up to 22 blood pressure measurements during pregnancy. It was conducted at Wuhan Children’s Hospital in China between September 2012 and October 2016. The average age of the participants was 28.3±3.6 years at delivery. Before pregnancy, 3,446 (21.1%) women were underweight (body mass index [BMI] < 18.5 kg/m²), 1,360 were overweight (BMI between 24.0 and 27.9 kg/m²), and only 224 (1.4%) were obese (BMI ≥ 28.0 kg/m²). 

Based on ACOG recommendations, the investigators diagnosed chronic hypertension based on a first blood pressure measurement taken at or before 20 weeks’ gestation while gestational hypertension was identified with the last blood pressure measurement taken with 1 month before delivery. Information on birth outcomes, including birth weight and gestational age at delivery, was retrieved from medical records. 

Using the 2017 ACC/AHA guidelines, the researchers were able to identify 2258 (13.8%) women with elevated blood pressure, 3422 (20.9%) women with hypertension stage 1, and 678 (4.2%) women with hypertension stage 2. When categorizing blood pressure using the yardstick in the ACOG statement, 5680 (34.8%) women were identified as having prehypertension and 678 (4.2%) were identified as having hypertension. Gestational hypertension was significantly associated with altered indicators of liver, renal, and coagulation functions during pregnancy for mothers and increased risk of adverse birth outcomes for newborns. 

When multivariable logistic regression models were applied, the odds ratio (OR) and 95% CI of hypertension stage 1 were 1.16 (95% CI, 0.83-1.61) for preterm delivery (PTD), 1.25 (95% CI 1.12-1.39) for early-term delivery (ETD) and 1.11 (95% CI 0.97-1.26) for small for gestational age (SGA). For hypertension stage 2, the ORs were 2.23 (95% CI, 1.18-4.24) for PTD, 2.05 (95% CI 1.67-2.53) for ETD and 1.43 (95% CI 0.97-1.26) for SGA. However, no significant associations were observed between elevated blood pressure and risk of adverse birth outcomes. 

The authors believe their findings indicate that adopting the 2017 ACC/AHA guideline would result in a substantial increase in prevalence of gestational hypertension. By expanding the definition of gestational hypertension, more women who may be at risk would receive the necessary care they might not have received using the yardstick recommended by ACOG.