Higher pulmonary arterial pressure is problem for pregnant women
Longer hospital stays found for pregnant PH patients in long-term study
For pregnant women with pulmonary hypertension (PH), higher pulmonary arterial pressure — blood pressure levels in the blood vessels that supply the lungs — is associated with longer hospital stays and a greater chance of being admitted to the intensive care unit (ICU).
That’s according to a new study by a team of U.S. researchers, which found that “ICU admission and prolonged hospitalization were common and associated with pulmonary arterial pressure” in pregnant PH patients.
The researchers noted that the Obstetric Comorbidity Index (OB-CMI) score, used to assess maternal risk based on the presence of high-risk conditions such as pulmonary arterial hypertension and congenital heart disease, was linked to ICU admission but not hospitalization length.
“Our findings suggest that existing general obstetric risk scores may not adequately capture the risk profile of pregnant women with pulmonary hypertension, highlighting the need for alternative risk assessment tools specific to this patient population,” the researchers wrote.
The study, “The Obstetric Comorbidity Index (OB-CMI) and its association with ICU admission and length of hospital stay in pregnant patients with pulmonary hypertension: A retrospective cohort study (1996-2025),” was published in the International Journal of Obstetric Anesthesia.
In PH, the increased blood pressure in the pulmonary arteries means the right side of the heart must work harder to pump blood, which can ultimately lead to right heart failure.
Having PH during pregnancy — which has been associated with adverse pregnancy outcomes — presents significant challenges due to the increased cardiovascular demands of carrying a child.
According to the researchers, however, predicting maternal outcomes in pregnancy has been difficult among the PH population, and the impact of having additional conditions besides PH itself remains unknown.
Pulmonary arterial pressure significantly associated with longer hospitalization
To learn more, a team led by researchers from Harvard Medical School in Boston conducted a retrospective analysis of pregnant women with PH followed up at Mass General Brigham and Tufts Medical Center between 1996 and 2025.
Their study evaluated 65 pregnancies in 61 women, who had a median age of 32.9 years. A higher proportion of the women — nearly half, or 47.7% — had mild PH. Moderate PH was seen among 30.8% of the women, while 18.5% had severe disease. The most common PH types were pulmonary arterial hypertension (46.1%) and PH due to left heart disease, also known as pulmonary venous hypertension (30.8%). Slightly more than half of the babies (56.9%) were born by cesarean section.
At delivery, the mother’s OB-CMI score was most commonly within the 5-9 range, although 43.1% of the patients had higher scores, indicating increased maternal risk.
More than half of the babies (56.9%) were born at term, while 43.1% were born preterm, or earlier than 37 weeks gestation. There were two stillbirths.
Among 53 babies whose birthweight was available, 21.5% had low weight (lower than 2.5 kg, or 5.5 pounds), and 6.1% were born with a weight greater than 4 kg (about 8.8 pounds).
Overall, the women stayed in the hospital for a median of six days after delivery, and almost a third required ICU care for a median of five days, the data showed. One-quarter of those requiring intensive care needed advanced cardiovascular support, while 15% received mechanical breathing support.
A total of 17 women were readmitted to the hospital within the first six months after delivery, mainly due to right heart failure or fluid accumulation.
Our study identified maternal pulmonary arterial pressure as the only predictor significantly associated with both the duration of hospitalization and the risk of ICU admission.
Two women (3%) died due to severe PH associated with heart failure, both before the year 2000. According to the researchers, this “was notably lower compared to prior studies,” which put maternal mortality at about 12%.
Maternal pulmonary arterial pressure was significantly associated with longer hospital stays, with a 15% increase in hospitalization time seen for each 1 mmHg pressure increase. Having a higher pulmonary pressure, a higher OB-CMI score, or a shorter pregnancy all were associated with a higher risk of ICU admission.
“Our study identified maternal pulmonary arterial pressure as the only predictor significantly associated with both the duration of hospitalization and the risk of ICU admission,” the researchers wrote.
The team noted as a limitation that the study was carried out at a single center in the northeastern U.S., which warrants caution in generalizing the findings to other healthcare settings or geographic regions.
“Future studies may investigate whether adjusting the weighting of pulmonary hypertension severity within the OB-CMI could improve its ability to predict severe maternal morbidity,” the researchers wrote.
The researchers suggested “refining the CMI scoring system to account for varying severities of pulmonary hypertension,” which they noted “could further improve its utility.”
In conclusion, the team said their findings “demonstrate that elevated pulmonary artery pressure … is significantly associated with ICU admission and prolonged hospitalization in pregnant patients with pulmonary hypertension.”
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