Chronic hypertension in women with pregestational diabetes

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Women with both pregestational diabetes and chronic hypertension pose a significantly increased risk for adverse perinatal outcomes, which appear to be additive to either condition alone, according to a study presented virtually at the Society for Maternal-Fetal Medicine’s (SMFM’s) 41st Annual Pregnancy Meeting.

The population-based retrospective study also concluded that the fetal growth pattern observed in these patients could represent the combined effect of hyperglycemia and placental insufficiency, “thus contributing to the increased rates of fetal death in this population,” said primary author Benjamin Muller, MD, a first-year maternal fetal medicine fellow at the Medical University of South Carolina in Charleston.

Muller and the other authors practice at a large academic referral center that provides care to a large population of women with multiple underlying medical comorbidities. “While it is clear preexisting diabetes and chronic hypertension adversely affect pregnancy outcomes, less is known about the increasingly common combined risk of these two conditions,” Muller told Contemporary OB/GYN.

The study used U.S. live birth and fetal death certificate data from 2018 to identify all singleton births occurring at more than 20 weeks’ gestation.

Of the 3,695,049 women included in the analysis, 0.8% had pregestational diabetes, 1.9% had chronic hypertension and 0.2% had both.

Women with both conditions were five times more likely to incur early fetal death up to 27 weeks’ 6 days gestation and seven times more likely to sustain late fetal death >28 weeks’ gestation.

Large and small for gestational age birthweights were also significantly more common in women with only pregestational diabetes or chronic hypertension

However, compared to pregestational diabetes alone, women with both conditions had reduced rates of large for gestational age birthweight (25.9% vs 30.2%), but increased rates of small for gestational age birthweight: 8.9% vs 6.3%.

“While initially these findings may seem like an improvement, it bears the question as to whether there is a masking effect of abnormal growth parameters from the combined effect of placental insufficiency and hyperglycemia,” Muller said. “In other words, are we missing fetuses at risk of still birth that could benefit from increased antenatal surveillance?”

As to why women with both pregestational diabetes and chronic hypertension have an increased risk for adverse perinatal outcomes, “there is still much left to speculation,” Muller said. “But it probably comes down to the unique pathophysiology of the disease processes themselves and their harmful effects on fetal growth, the placenta and maternal-fetal vasculature.”

However, due to reliance on birth and death certificate data, the investigators were unable to evaluate important differences between type 1 and type 2 diabetes, as well as severity of disease, for glycemic control and need for antihypertensives. “It is likely that some aspect of the increased risks identified in our study is a result of greater disease severity if a woman has both diabetes and chronic hypertension rather than an entirely additive affect,” Muller said.

Significant racial differences also existed in the study population, with non-Hispanic Black women having the highest proportion of both comorbidities in pregnancy. “This group may benefit from future interventions aimed at reducing healthcare disparities,” Muller said.

The investigators stressed the importance of preconception counseling in the study population, including trying to prevent adverse outcomes with optimization of underlying comorbidities prior to conception. “Clinicians should thoroughly counsel patients on their pregnancy-related risks and employ close antenatal fetal surveillance,” Muller said.

Given the fetal growth pattern seen in the study’s data, it is possible that umbilical artery Doppler may be of benefit beyond standard fetal weight thresholds routinely used to initiate such surveillance.

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Muller reports no relevant financial disclosures.