Impact of stage 1 hypertension in the first and second trimesters on adverse pregnancy outcomes: The Japan Environment and Children's study (JECS)

Abstract

Objectives: To investigate the association between stage 1 hypertension, defined as systolic blood pressure (BP) of 130-139 mmHg or diastolic BP of 80-89 mmHg, in the first and second trimesters and the risk of adverse pregnancy outcomes.

Study design: We analyzed 79,249 singleton pregnancies from a nationwide birth cohort study. BP in the first and second trimesters was classified into normal, elevated, stage1 hypertension, and stage 2 hypertension. We examined the risk of adverse pregnancy outcomes in each group using multivariable logistic regression analysis. We also investigated the influence of BP changes between the first and second trimesters on adverse pregnancy outcomes.

Main outcome measures: Overall preterm birth (PTB < 37 weeks), early PTB (<34 weeks), and small for gestational age (SGA).

Results: Stage 1 hypertension in the first trimester was associated with increased risks of overall PTB (aOR, 1.23; 95 %CI, 1.08-1.39), early PTB (aOR, 1.38; 95 %CI, 1.07-1.79), and SGA (aOR, 1.19; 95 %CI, 1.04-1.36) compared to normal BP. These risks were more evident in the second trimester; overall PTB (aOR, 1.87; 95 %CI, 1.64-2.14), early PTB (aOR, 2.21; 95 %CI, 1.69-2.87), and SGA (aOR, 1.38; 95 %CI, 1.18-1.62). The risk of PTB was higher among women with an upward BP trajectory between the first and second trimesters.

Conclusions: Stage 1 hypertension in the first and second trimesters was associated with increased risks of overall PTB, early PTB, and SGA. Monitoring the BP trajectory for stage 1 hypertension may be useful for identifying high-risk groups.

Keywords: Blood pressure trajectory; Early preterm birth; Hypertensive disorders of pregnancy; Preterm birth; Small for gestational age; Stage 1 hypertension.