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Pregnant women diagnosed with chronic hypertension and diabetes appeared to avoid poorer outcomes if they maintained a blood pressure below some current guidelines, a researcher reported.

In a secondary analysis of the study, a blood pressure below 130/80 mm Hg was associated with a relative 57% lower risk of a composite of adverse clinical events, with a 22.6% rate compared with 51.6% when blood pressure fell between 130/80 mm Hg and the guideline-indicated threshold of 140/90 mm Hg (P<0.01).

Individual components of the primary endpoint all favored maintaining a lower blood pressure as well, reported Lorie Harper, MD, MSCI, of the University of Texas at Austin Dell Medical School, in a presentation at the Society for Maternal-Fetal Medicine meeting.

Comparing the lower and higher blood pressure groups:

• Preeclampsia with severe features occurred in 19.4% vs 43.8% (P<0.01)
• Indicated preterm birth before 35 weeks of gestation occurred in 8.3% vs 23% (P<0.01)
• Placental abruption occurred in two vs six cases (less than 1% vs 2.8%, P=0.50)

And that decreased risk of adverse outcomes came without increasing the risk of small for gestational age, Harper said. "Treating to this lower goal during pregnancy should be considered."

Jamie Lo, MD, of Oregon Health Sciences University in Portland, told MedPage Today that "in general, we try to get our pregnant patients' blood pressure to be less than 140/80, as per American College of Obstetricians and Gynecologists recommendations."

"I think that Dr. Harper's study suggests we should consider a different blood pressure range for our diabetic pregnant individuals," said Lo, who was not involved in the study. "Larger randomized control trials would be needed to better assess this."

CHAP was originally designed to confirm the safety and benefit in pregnancy of the otherwise standard recommendation for reducing blood pressure to under 140/90 mm Hg compared to withholding blood pressure medication until women reached severe hypertension (>160/105 mm Hg). It changed the field by showing that lower was better, without harming babies or mothers.

Harper said that the fear was lowering blood pressure too much could restrict blood flow to the fetus and cause developmental problems.

Since below 140/90 became the standard of care with report of the CHAP findings in April 2022, the researchers wanted to see if an even lower threshold would be even better, in line with recommendations of the American College of Cardiology and the American Diabetes Association.

From that original study, researchers scrutinized a subset of patients who also were diagnosed with diabetes. Out of the original 2,325 subjects in CHAP, 434 met requirements for the current substudy.

CHAP enrolled women with mild chronic hypertension who were less than 23 weeks into their pregnancy. Only single pregnancies were eligible for the study.

The secondary analysis cohort averaged 33 years old, with the majority being Black or Hispanic women. About 25% of the group were white. About 60% of the participants had Medicaid insurance. About 31% were high school graduates; another 24% were college graduates. About half the participants were married. BMI averaged around 41 at enrollment.

Of the secondary analysis participants, 217 women had achieved a blood pressure below 130/80 mm Hg and another 217 had achieved blood pressures in the 130-139/80-89 mm Hg range. At baseline, their blood pressures averaged 135.9/80.6 and 139.8/86.5 mm Hg, respectively. During pregnancy, blood pressure averaged 127.1/75 and 135/84.1 mm Hg, respectively.

Among the secondary endpoints, admission to neonatal intensive care unit was required by 84 children born to women in the lower blood pressure group compared with 53% of the children whose mothers fell in the higher blood pressure range (P=0.003).

Days spent in the neonatal intensive care unit were lower for the babies of the mothers with lower blood pressure, at 14.7 versus 26.1 days (P=0.02).

Cesarean delivery was similarly common between groups, as was fetal or neonatal mortality, which occurred in two cases among the women in the lower blood pressure group compared with seven among those with higher blood pressure (P=0.17).

The average weight of newborns among women in the lower blood pressure cohort was 3.2 kg, compared with 2.8 kg among the women with higher blood pressure (P<0.01).

Limitations included the retrospective analysis, potential for confounding by indication, and a slight predominance of newly diagnosed diabetes in the lower blood pressure group.

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