Tighter BP control improves pregnancy outcomes in women with DM, chronic hypertension

Jairia Dela Cruz
23 Feb 2023
CHAP backs BP control during pregnancy, even for mild hypertension

Further lowering blood pressure (BP) helps cut the risk of adverse perinatal events for pregnant women with pregestational diabetes mellitus (DM) and mild chronic hypertension, according to the secondary analysis of the Chronic Hypertension and Adverse Pregnancy (CHAP) study presented at SMFM 2023.

Compared with an average BP of 130–139/80–89 mm Hg, BP levels below 130/80 mm Hg was associated with a lower frequency of the primary composite outcome of adverse perinatal events (22.6 percent vs 51.6 percent; adjusted relative risk [aRR], 0.43, 95 percent confidence interval [CI], 0.33–0.57; p<0.01). [SMFM 2023, abstract 18]

Likewise, individual components of the primary outcome occurred with significantly lower frequency when BP was maintained below 130/80 mm Hg. These included pre-eclampsia with severe features (19.4 percent vs 43.8 percent; aRR, 0.44, 95 percent CI, 0.32–0.60; p<0.01) and indicated preterm birth <35 weeks (8.3 percent vs 23.0 percent; aRR, 0.36, 95 percent CI, 0.22–0.60; p<0.01) with the exception of placental abruption (p=0.50).

Another notable finding is that tighter BP control helped reduce the risk of adverse perinatal outcomes without increasing the risk of small for gestational age (birth weight <10th percentile: 9.2 percent vs 5.1 percent; aRR, 0.53, 95 percent CI, 0.26–1.10; p=0.10) or foetal or neonatal death (<1 percent vs 3.2 percent; aRR, 0.26, 95 percent CI, 0.05–1.22; p=0.17), reported lead study author Dr Lorie Harper, an associate professor at the University of Texas Dell Medical School, Austin, Texas, US.

In light of the findings, Harper said: “Treating to this lower goal during pregnancy should be considered.”

Before reducing BP to levels below 140/90 mm Hg became the standard of care in line with the recommendations of the American College of Cardiology, chronic hypertension during pregnancy was managed by reserving BP treatment for severe hypertension (>160/105 mm Hg), Harper noted.

Furthermore, there is the fear that lowering BP too much could restrict the flow of blood to the foetus and cause growth problems, she added.

Already, the primary findings of CHAP demonstrated that lowering the BP target to below 140/90 mm Hg during pregnancy is beneficial, being associated with better pregnancy outcomes with no increase in the risk of small-for-gestational-age birth weight as compared with a strategy of withholding treatment until severe hypertension. [N Engl J Med 2022;386:1781-1792]

Data from the secondary analysis of CHAP suggest that an even lower BP target threshold would be even better in mild chronic hypertension in pregnant patients with pregestational diabetes.

The secondary analysis included 434 participants (average age 33.5 years), of which 217 had an average BP of <130/80 mm Hg and 217 had an average BP of 130–139/80–89 mm Hg. Baseline characteristics were largely similar in the two groups.

The study was limited by its retrospective nature, the potential for confounding by indication, and a slightly higher number of newly diagnosed diabetes in the lower BP group.

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