Introduction
Pulmonary hypertension is a complex and progressive disorder characterized by elevated pulmonary arterial pressure, leading to high maternal morbidity and mortality during pregnancy. Clinically, pulmonary hypertension is defined by a mean pulmonary artery pressure of 25 mm Hg or greater at rest, as measured during right heart catheterization.1 Pulmonary hypertension severity is typically categorized as mild (pulmonary artery systolic pressure [PASP] 35–50 mm Hg), moderate (PASP 50–70 mm Hg), or severe (PASP >70 mm Hg). Based on etiology, the most common pulmonary hypertension subgroup is idiopathic pulmonary arterial hypertension, accounting for more than 50% of cases.2
The intersection of pulmonary hypertension and pregnancy presents significant clinical challenges due to the increased cardiovascular demands of the physiologic changes of pregnancy. In patients with pulmonary hypertension, these adaptations can lead to acute right ventricular failure, circulatory collapse, and increased mortality rates. Previous studies have reported maternal mortality rates ranging from 9 to 56% among pregnant women with pulmonary hypertension, underscoring the severity of the condition.3–8 Given these substantial risks, current clinical guidelines and the World Health Organization (WHO) recommend avoidance of pregnancy or early termination for patients with severe pulmonary hypertension to prevent maternal mortality.7,9–11
Prediction of maternal outcomes in pregnant patients with pulmonary hypertension has been challenging due to the rarity of the disease and limited patient populations available to study.3,4,7,12–15 While pulmonary hypertension severity, assessed by pulmonary artery pressure, has been linked to adverse outcomes,3–7,9–11,13,15,16 comprehensive evaluations of additional clinical predictors remain limited. Furthermore, it is unknown whether the presence of clinical comorbidities, other than pulmonary hypertension itself, contribute significantly to worse maternal outcomes. Recently, the obstetric comorbidity index (OB-CMI) was introduced to describe the comorbidity burden of pregnant patients.17,18 This tool is based on the weighted sum of the presence of high-risk conditions. Based on this scoring system, conditions such as severe preeclampsia, pulmonary arterial hypertension, and congenital heart disease confer the highest maternal risk. While the OB-CMI predicts the risk of extended stay for delivery and intensive care unit (ICU) admission in the general pregnancy population,19,20 its predictive power in pregnant patients with pulmonary hypertension, who already have elevated risk, has not been investigated.
In our retrospective study, we aimed to analyze the maternal and neonatal outcomes in patients with pulmonary arterial hypertension treated at two large healthcare systems in Boston over the past 26 years. Specifically, we investigated factors associated with prolonged hospitalization and the need for ICU admission, focusing on whether additional comorbidities, as measured by higher OB-CMI scores beyond those assigned for pulmonary hypertension, contributed to worse maternal outcomes. We hypothesized that pregnant patients with pulmonary hypertension who have additional comorbid conditions (resulting in higher OB-CMI scores beyond the baseline score for pulmonary hypertension) would experience increased rates of ICU admission and prolonged hospitalization. Clarifying these relationships could inform risk stratification, enhance clinical decision-making, and improve management strategies for this high-risk obstetric population.
Methods
Study Design
The study was a retrospective multi-center cohort study investigating the clinical outcomes of labor and delivery amongst obstetric patients with pulmonary hypertension within the Massachusetts General Brigham (MGB) and Tufts Medical Center (TMC) between 1996 – July 2025. Institutional review board approval was obtained from the MGB and TMC Institutional Review Board, protocol # 2020P002859 and IRB ID STUDY00003513, respectively, with a waiver of patient consent. Cases were initially identified using the International Classification of Disease-9/10 code I27, indicating “other pulmonary heart disease.” A chart review was completed by S.A., D.V., and V.K. at MGB and E.L. and D.D. at TMC to confirm the diagnosis during the peripartum period. There was no standardized peripartum management protocol across both institutions during the study period. Instead, care involved a multidisciplinary approach tailored to each individual, incorporating obstetric anesthesia, maternal-fetal medicine, cardiology, critical care, and neonatology specialists. All patients received individualized counseling regarding maternal and fetal risks.
Inclusion and Exclusion Criteria
Diagnosis of pulmonary hypertension in the electronic health record (EHR) was confirmed based on a documented pulmonary artery systolic pressure (PASP) >37 mm Hg via echocardiography or a pulmonary artery mean pressure ≥25 mm Hg via right heart catheterization.1,21,22 We used an echocardiographic PASP cutoff > 37 mm Hg because of high specificity and sensitivity in identifying patients with pulmonary hypertension.22 Whenever possible, cardiac catheterization results were referenced. In the absence of right ventricular outflow tract obstruction, the right ventricular systolic pressure (RVSP) was assumed to equal the PASP. The etiology of pulmonary arterial hypertension was categorized according to the WHO clinical classifications.22 The WHO classification categorizes pulmonary hypertension into five groups: Group 1, pulmonary arterial hypertension; Group 2, pulmonary hypertension due to left-heart disease; Group 3, pulmonary hypertension due to chronic lung disease or hypoxia; Group 4, chronic thromboembolic pulmonary hypertension; and Group 5, pulmonary hypertension due to unclear or multifactorial mechanisms. Exclusion criteria included a PASP of less than 37 mmHg at the time of pregnancy, despite a history of clinical diagnosis of pulmonary arterial hypertension or incomplete EHR information.
Data Collection
Patient demographic information included maternal age at birth, self-reported race and ethnicity, and OB-CMI score. The latter was calculated exactly as described by Easter et al,17 assigning pulmonary hypertension itself a score of 4 and using data from the progress note immediately preceding the delivery note in the medical record. Pregnancy-related characteristics included gravidity, parity, mode of delivery, mode of induction (if used), and anesthesia type.
Maternal outcomes included maternal mortality and its cause, duration of hospital and ICU stay, readmission within six months postpartum, and significant medical interventions during hospitalization (e.g., extracorporeal membrane oxygenation (ECMO) support, advanced respiratory or cardiovascular therapies, emergency procedures). Neonatal outcomes included gestational age at delivery, birth weight, Apgar scores, and neonatal mortality. Admission notes were reviewed to confirm active clinical diagnoses that may not have been explicitly documented elsewhere.
Statistical Analysis
The primary outcomes were length of hospital stay (continuous variable, in days) and ICU admission (binary: yes/no). Categorical variables were summarized as frequencies (%), and numerical variables were presented as mean ± standard deviation or median (25–75% interquartile range), depending on the distribution. For ICU admission, we used univariate logistic regression; for length of hospital stay, we fitted a log-linear regression after natural-log transformation of length of stay to correct right skew. Regression coefficients were exponentiated and are therefore interpreted as multiplicative effects on length of stay (exp β). Statistical analyses were performed using Python (version 3.10), with statistical significance defined by two-tailed P values <0.05.
Results
A total of 65 pregnancies among 61 patients were included in the final cohort after reviewing 117 pregnancies; 49 of those were excluded due to incomplete data or inability to confirm the pulmonary hypertension diagnosis; 3 patients developed the condition postpartum (Supplementary Fig. S1). We observed an increasing number of pregnancies complicated by pulmonary hypertension in recent years, especially after 2015 (Supplementary Fig. S2). All patients were admitted to a tertiary care hospital between 1996 and 2025 for delivery. Patient demographic data are presented in Table 1. The majority of patients self-identified as belonging to a racial or ethnic minority.
Table 1.
Characteristics of pregnant patients with pulmonary hypertension.
| Combined (n = 65) | Mass General Brigham (n = 55) | Tufts Medical Center (n = 10) | |
|---|---|---|---|
| Age (years) | 32.9 (28.9–36.6) | 32.9 (28.7–36.6) | 33.0 (30.9–34.6) |
| BMI (kg/m2) | 30.4 (26.1–34.8) | 31.0 (26.6–35.1) | 27.7 (23.2–32.8) |
| Self-reported race (n) | |||
| White | 24 (36.9%) | 22 (40.0%) | 2 (20.0%) |
| Black | 20 (30.8%) | 15 (27.3%) | 5 (50.0%) |
| Asian | 3 (4.6%) | 2 (3.6%) | 1 (10.0%) |
| Other | 9 (13.8%) | 8 (14.5%) | 1 (10.0%) |
| Unavailable | 9 (13.8%) | 8 (14.5%) | 1 (10.0%) |
| Self-reported ethnicity (n) | |||
| Not Hispanic | 39 (60.0%) | 31 (56.4%) | 8 (80.0%) |
| Hispanic | 16 (24.6%) | 15 (27.3%) | 1 (10.0%) |
| Unavailable | 10 (15.4%) | 9 (16.4%) | 1 (10.0%) |
| Parity (n) | |||
| Nulliparous | 15 (23.1%) | 14 (25.4%) | 1 (10.0%) |
| Multiparous | 50 (76.9%) | 41 (74.5%) | 9 (90.0%) |
Data are presented as median (25–75% interquartile range) or n (%).
Clinical characteristics related to pulmonary hypertension severity, delivery mode, and management are presented in Table 2. Pulmonary arterial hypertension (WHO Group 1) was the most common subtype (n=30; 46.15%). The median OB-CMI score at delivery was 9 (range: 4–24). Detailed descriptions of the OB-CMI scoring components and their respective patient counts are provided in Supplementary Table S1. Twenty-six (40.0%) had vaginal deliveries (spontaneous n=18, forceps-assisted n=6, vacuum-assisted n=2). Thirty-seven (56.9%) had cesarean deliveries, of which 27 were scheduled and 10 were urgent/emergent. Lastly, one patient had an intrauterine fetal demise at 24 weeks, and one patient had a dilation and evacuation at 23.6 weeks due to maternal health deterioration.
Table 2.
Pulmonary hypertension status and delivery management.
| Combined (n = 65) | Mass General Brigham (n = 55) | Tufts Medical Center (n = 10) | |
|---|---|---|---|
| OB-CMI Score at Deliverya | |||
| 4 | 3 (4.6%) | 2 (3.6%) | 1 (10.0%) |
| 5 – 9 | 34 (52.3%) | 28 (50.9%) | 6 (60.0%) |
| 10+ | 28 (43.1%) | 25 (45.4%) | 3 (30.0%) |
| Pulmonary Hypertension Severity | |||
| Mild | 31 (47.7%) | 26 (47.3%) | 5 (50.0%) |
| Moderate | 20 (30.8%) | 16 (29.1%) | 4 (40.0%) |
| Severe | 12 (18.5%) | 12 (21.8%) | 0 (0.0%) |
| Pulmonary Hypertension WHO Categoryb | |||
| Group 1 | 30 (46.1%) | 25 (45.4%) | 5 (50.0%) |
| Group 2 | 20 (30.8%) | 16 (29.1%) | 4 (40.0%) |
| Group 3 | 13 (20.0%) | 13 (23.6%) | 0 (0.0%) |
| Group 4 | 1 (1.5%) | 0 (0.0%) | 1 (10.0%) |
| Group 5 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Mode of Delivery | |||
| Spontaneous vaginal delivery | 18 (27.7%) | 14 (25.4%) | 4 (40.0%) |
| Forceps-assisted vaginal delivery | 6 (9.2%) | 5 (9.1%) | 1 (10.0%) |
| Vacuum-assisted delivery | 2 (3.1%) | 2 (3.6%) | 0 (0.0%) |
| Scheduled cesarean delivery | 27 (41.5%) | 22 (40.0%) | 5 (50.0%) |
| Urgent cesarean delivery | 10 (15.4%) | 10 (18.2%) | 0 (0.0%) |
| D&E/TAB | 2 (3.1%) | 2 (3.6%) | 0 (0.0%) |
| Anesthesia/analgesia mode | |||
| Epidural | 45 (69.2%) | 38 (69.1%) | 7 (70.0%) |
| Spinal | 6 (9.2%) | 5 (9.1%) | 1 (10.0%) |
| Combined spinal epidural | 7 (10.8%) | 7 (12.7%) | 0 (0.0%) |
| General | 4 (6.1%) | 3 (5.4%) | 1 (10.0%) |
| Labor Management | |||
| Labor Induced | 29 (44.6%) | 25 (45.4%) | 4 (40.0%) |
Abbreviations OB-CMI, Obstetric Comorbidity Index; WHO, World Health Organization; D&E, dilation and evacuation; TAB, therapeutic abortion.
Data are presented as n (%).
The OB-CMI score categories (4, 5–9, ≥10) are based on previously established risk stratification methods that correlate higher scores with increased maternal morbidity risk (Easter et al. 2019).17
WHO pulmonary hypertension groups: Group 1, pulmonary arterial hypertension; Group 2, pulmonary hypertension due to left-heart disease; Group 3, pulmonary hypertension due to chronic lung disease or hypoxia; Group 4, chronic thromboembolic pulmonary hypertension; Group 5, pulmonary hypertension due to unclear or multifactorial mechanisms.
The median hospital length of stay was 6 days (IQR 4–10), with 20 patients (30.8%) requiring ICU admission (Table 3). The median ICU stay was 5 (IQR 1.3 – 9.3) days. Among patients admitted to the ICU (n=20), 5 (25.0%) required advanced cardiovascular support with vasopressors or inotropes, and 3 (15.0%) received mechanical ventilatory support during their ICU stay. Four patients underwent prophylactic percutaneous ECMO cannulation during cesarean delivery; however, none ultimately required ECMO support. Notably, all prophylactic ECMO placements occurred exclusively among patients with severe pulmonary hypertension (PASP ≥70 mm Hg). Hospital readmission within six months postpartum occurred in 17 patients (26.1%), primarily due to heart failure associated with right ventricular dysfunction or fluid overload; other reasons included preeclampsia, wound infections, and mental health crises.
Table 3.
Maternal Outcomes in Patients with Pulmonary Hypertension.
| Combined (n = 65) | Mass General Brigham (n = 55) | Tufts Medical Center (n = 10) | |
|---|---|---|---|
| Maternal mortality (n) | 2 (3.1%) | 2 (3.6%) | 0 (0.0%) |
| ICU admission (n) | 20 (30.8%) | 16 (29.1%) | 4 (40.0%) |
| Duration of hospitalization for delivery (days) | 6 (4–10) | 6 (4 −11) | 4 (3–9) |
| Number of patients with readmission within 6 months after delivery (n) | 17 (26.1%) | 15 (27.3%) | 2 (20.0%) |
Abbreviations: ICU, intensive care unit; ED, emergency department
Data are presented as median (25–75% interquartile range) and n (%).
Overall maternal mortality was 3% (2 of 65), with both maternal deaths occurring before the year 2000. Both fatalities were associated with severe pulmonary hypertension (PASP ≥70 mm Hg) complicated by postpartum cardiac decompensation and heart failure despite aggressive treatment. The OB-CMI scores for these patients were 5 and 12, respectively.
For anesthesia and analgesia management, epidural anesthesia was the most utilized technique (n=45; 69.2%), followed by combined spinal-epidural anesthesia (n=7; 10.8%) and spinal anesthesia (n=6; 9.2%). General anesthesia was used in 4 cases (6.1%) due to either contraindications to neuraxial anesthesia (e.g., anticoagulation, patient refusal) (n=3) or intraoperative events necessitating conversion from neuraxial to general anesthesia, such as neuraxial anesthesia failure (n=1).
Neonatal outcomes are summarized in Table 4. Apart from two stillbirths, there were no additional neonatal deaths. Of the 65 deliveries, 28 (43.1%) were born preterm (<37 weeks) and 37 (56.9%) at term (≥37 weeks). Birthweight information was available for 53 neonates, of whom 14 (21.5%) had low birth weight (<2.5 kg), and four neonates (6.1%) had macrosomia (>4.0 kg).
Table 4.
Neonatal Outcomes in Patients with Pulmonary Hypertension.
| Combined (n = 65) | Mass General Brigham (n = 55) | Tufts Medical Center (n = 10) | |
|---|---|---|---|
| Gestational age at delivery | |||
| Preterm (<37 weeks) | 28 (43.1%) | 24 (43.6%) | 4 (40.0%) |
| Term (>=37 weeks) | 37 (56.9%) | 31 (56.4%) | 6 (60.0%) |
| Weight | |||
| Low birth weight (<2.5 kg) | 14 (21.5%) | 11 (20.0%) | 3 (30.0%) |
| Normal birth weight (2.5–4.0 kg) | 35 (53.8%) | 30 (54.5%) | 5 (50.0%) |
| Macrosomia (>4.0 kg) | 4 (6.1%) | 3 (5.4%) | 1 (10.0%) |
| Apgar at 1 min | |||
| Severely or moderately depressed (<7) | 14 (21.5%) | 6 (21.8%) | 2 (20.0%) |
| Excellent condition (7–10) | 49 (75.4%) | 41 (74.5%) | 8 (80.0%) |
| Apgar at 5 min | |||
| Severely or moderately depressed (<7) | 6 (9.2%) | 5 (9.1%) | 1 (10.0%) |
| Excellent condition (7–10) | 57 (87.7%) | 48 (87.3%) | 9 (90.0%) |
Data are presented as n (%).
Pulmonary artery pressure was significantly associated with prolonged hospital stay (exp β = 1.15; 95% CI 1.05–1.27; P =0.004), indicating a 15% increase in hospital stay per 1-mm Hg increase. Pulmonary artery pressure (OR 1.03, 95% CI 1.00–1.07; P =0.027) and OB-CMI score (OR 1.14, 95% CI 1.00–1.29; P =0.046) demonstrated borderline statistically significant associations with ICU admission; OB-CMI score was not associated with hospital stay duration (exp β = 1.13, 95% CI 0.73–1.73; P =0.580). Other findings included a statistically significant association between lower neonatal gestational age and higher odds of ICU admission (OR 0.83, 95% CI 0.71–0.96; P =0.013), and a borderline association of parity with ICU admission (OR 1.63, 95% CI 1.00–2.65; P =0.048) (Tables 5 and 6).
Table 5.
Univariate regression of length of hospital stay in pregnant patients with pulmonary hypertension.
| Predictor | Exp β* (95 % CI) | P |
|---|---|---|
| Self-reported race/ethnicity | ||
| Self-reported race, White (vs non-White) | 1.32 (0.03–57.92) | 0.884 |
| Self-reported race, Black (vs non-Black) | 0.88 (0.02–45.71) | 0.947 |
| Self-reported race, Other (vs all others) | 0.03 (0.0–6.09) | 0.196 |
| Self-reported ethnicity, Hispanic (vs non-Hispanic) | 0.32 (0.0–21.71) | 0.589 |
| Maternal age (per year) | 0.87 (0.65–1.18) | 0.376 |
| Anesthesia/analgesia mode | ||
| Epidural | 0.07 (0.0–3.63) | 0.186 |
| Combined spinal epidural | 19.5 (0.06–6717.62) | 0.313 |
| General | 14.47 (0.01–27991.19) | 0.483 |
| Spinal | 4.38 (0.01–2377.74) | 0.641 |
| Obstetric factors | ||
| Gravidity | 0.74 (0.3–1.84) | 0.510 |
| Parity | 0.6 (0.12–3.0) | 0.531 |
| Newborn gestational age (per week) | 0.66 (0.41–1.05) | 0.076 |
| Macrosomia | 1.01 (0.0–2009.33) | 0.998 |
| Clinical parameters | ||
| Pulmonary artery pressure (per mm Hg) | 1.15 (1.05–1.27) | 0.004 |
| OB-CMI score | 1.13 (0.73–1.73) | 0.579 |
Linear regression on ln(length of stay). Exp β represents the multiplicative change in length of stay for a 1-unit increase (continuous predictors) or for the presence vs absence of a category (binary predictors). Abbreviations: OB-CMI, Obstetric Comorbidity Index.
Table 6.
Univariate regression of ICU admission in pregnant patients with pulmonary hypertension.
| Predictor | Odds ratio (95% CI) | P |
|---|---|---|
| Sociodemographic factors | ||
| Self-reported race, White | 0.64 (0.21–1.98) | 0.442 |
| Self-reported race, Black | 0.67 (0.2–2.18) | 0.503 |
| Self-reported race, Other | 2.0 (0.48–8.42) | 0.344 |
| Self-reported ethnicity, Hispanic | 2.15 (0.67–6.97) | 0.200 |
| Maternal age | 1.03 (0.94–1.13) | 0.483 |
| Anesthesia/analgesia mode | ||
| Epidural | 2.21 (0.63–7.74) | 0.216 |
| Combined spinal epidural | 0.89 (0.16–5.02) | 0.894 |
| Obstetric factors | ||
| Gravidity | 1.3 (0.98–1.73) | 0.066 |
| Parity | 1.63 (1.0–2.65) | 0.048 |
| Newborn gestational age, weeks | 0.83 (0.71–0.96) | 0.013 |
| Clinical parameters | ||
| Pulmonary artery pressure | 1.03 (1.0–1.07) | 0.027 |
| OB-CMI score | 1.14 (1.0–1.29) | 0.046 |
Data are presented as odds ratio with 95% confidence intervals (CI) and P values. Abbreviations: OB-CMI, Obstetric Comorbidity Index.
Discussion
This retrospective multicenter cohort study confirmed that increased pulmonary artery pressure, a well-established indicator of pulmonary hypertension severity, was significantly associated with both ICU admission and prolonged hospitalization. While there is limited data in the existing literature regarding the length of hospital stay specifically, our findings on ICU admission align closely with a recent meta-analysis, which demonstrated significantly lower ICU admission rates in patients with mild pulmonary hypertension compared to those with moderate or severe disease (RR 0.37; 4 studies, n=269).23 However, contrary to our initial hypothesis, the OB-CMI, previously validated as a predictor of adverse outcomes in the general obstetric population,17,19 was not significantly associated with these outcomes in our cohort. 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 maternal mortality of 3% observed in our cohort was notably lower compared to prior studies, including a recent systematic review estimating maternal mortality at approximately 12% from global data collected between 2008 and 2018.3–8 Similarly, perinatal mortality of 1% in our cohort was lower than the previously reported global average of 4%.3 Both maternal deaths in our study occurred early in the observation period (prior to the year 2000), and the absence of mortality in subsequent years likely reflects improvements in clinical management, patient counseling, and earlier disease diagnosis. Such improvements may be attributable to greater awareness of pulmonary hypertension risks in pregnancy, advances in multidisciplinary care at tertiary academic institutions in the USA, and overall enhanced patient management. However, published findings have varied significantly, with Meng et al.5 reporting maternal mortality of 23% in a recent cohort from four tertiary-care academic centers in the USA. International maternal mortality rates reported by systematic reviews have decreased from 38% in 1978–1996 to 12% in 2008–2018, suggesting that improved practice may have contributed to better outcomes.3,5 Additionally, our slightly more favorable outcomes might be partially explained by patient selection bias; in line with existing guidelines, many patients diagnosed with pulmonary hypertension likely received strong counseling to avoid or terminate pregnancy, resulting in fewer pregnancies and deliveries among women with pulmonary hypertension.
Despite the evolution of clinical practices for managing pregnant patients with pulmonary hypertension, maternal morbidity in our cohort remained substantial, as evidenced by prolonged hospitalizations and frequent ICU admissions, consistent with recent literature.4,5,8 Our findings thus raise the question of whether pulmonary hypertension should continue to be universally regarded as an absolute contraindication to pregnancy, particularly among carefully selected patients receiving comprehensive multidisciplinary care. Although guidelines from 2015 strongly recommended against pregnancy or early termination due to the high maternal risk,6,7 newer guidelines emphasize shared decision-making for patients with well-controlled pulmonary hypertension and lower-risk profiles.8,9,23 Our findings, along with recent data from specialized centers,8,9 suggest a need for continued refinement of clinical guidelines to reflect these evolving outcomes and practice patterns and recognition of patient autonomy in pregnancy decision-making.
While our cohort had lower than expected maternal mortality, the morbidity associated with these pregnancies was still prominent, especially compared to outcomes in the general population.16 For example, more patients in our cohort required ICU admission than the national average8 (30.8% vs. 0.18%). Moreover, over 9% of infants in our cohort had an abnormal Apgar score (0 to 6) at 5 minutes, whereas this figure was suggested to be only 1% nationally by a large 2022 study.12 Interestingly, multiparity and preterm delivery were associated with an increased risk of ICU admission; however, given our small sample size and the fact that the majority (77%) of our patients were multiparous, these findings should be interpreted cautiously. Further investigation in larger cohorts is needed to clarify its clinical significance.
The evidence to guide the management of patients with pulmonary hypertension is lacking.6 While some guidelines provide recommendations (i.e., the Pulmonary Vascular Research Institute recommends cesarean section to serve as the preferred mode of delivery),9 they are only based on expert opinion and do not have a consistent evidentiary basis. The high rates of adverse outcomes experienced by our cohort shed light on the significant morbidity experienced by pregnant patients with pulmonary hypertension and emphasize the need for further research to better inform guidelines for improved patient care.
Lastly, our findings suggest no significant association between the OB-CMI and maternal morbidity in pregnant patients with pulmonary hypertension. While the OB-CMI has been validated for use in the general obstetric population and represents a significant advancement in risk assessment, its applicability to patients with pulmonary hypertension may be limited. In the OB-CMI, pulmonary hypertension is weighted similarly to placenta previa, despite global maternal mortality being significantly higher among patients with pulmonary hypertension (12%) compared to those with placenta previa (4–8%).2,3,13 Furthermore, while the OB-CMI may be useful in determining the overall complexity of a patient at the time of delivery, it does not distinguish between different severities of pulmonary hypertension, which may make it less reliable in determining outcomes.
OB-CMI is one of several obstetric comorbidity indices currently in use. While previous research indicates that the OB-CMI demonstrates moderate predictive performance and may outperform other indices, its general applicability has been questioned, especially across diverse clinical contexts and datasets.24 Our results confirm the limited predictive utility of OB-CMI specifically among pregnant patients with pulmonary hypertension, thereby directly addressing previous recommendations to investigate its feasibility and reliability in specialized clinical populations.24
Additionally, other prediction models specifically developed for acute obstetric settings, such as the Modified Early Obstetric Warning Score (MEOWS) and the Collaborative Integrated Pregnancy High-dependency Estimate of Risk (CIPHER), might offer better predictive utility in acute high-risk clinical scenarios.25 Future research could focus on evaluating these acute-care-oriented models within the context of pulmonary hypertension in pregnancy, potentially improving risk stratification and management strategies in this high-risk obstetric population.
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. 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 and related clinical outcomes, such as ICU admission and prolonged hospitalization. Additionally, refining the OB-CMI scoring system to account for varying severities of pulmonary hypertension could further improve its utility. Specifically, integrating the established classifications of pulmonary hypertension based on PASP (i.e., mild (35–50 mm Hg), moderate (50–70 mm Hg), and severe (>70 mm Hg)) may enhance the index’s ability to stratify risk.14 These modifications could significantly improve the OB-CMI’s effectiveness in identifying patients at increased risk for severe maternal morbidity.
Study Limitations
Our study has several limitations. First, despite encompassing patients from the past 26 years, the cohort size remained relatively small. Second, incomplete or limited data availability from earlier medical records restricted our ability to perform more extensive statistical analyses. Third, despite extensive chart review, variability in provider documentation could have resulted in underestimation of some OB-CMI scores. However, significant missing data are unlikely, as most OB-CMI components (e.g., autoimmune disease, diabetes, asthma) are important medical considerations in pregnancy with associated treatments and are unlikely to be excluded from patients’ notes and care plans. Fourth, although the cohort included patients from multiple community-level hospitals, those with severe disease were either initially managed or transferred to tertiary care facilities. Additionally, this study was conducted at academic medical centers in the Northeastern USA, which may limit the generalizability of the findings to other healthcare settings or geographic regions. Finally, we relied solely on pulmonary artery pressure as an indicator of pulmonary hypertension severity. Other important severity measures, such as pulmonary vascular resistance, right ventricular function, and functional status (e.g., NYHA classification or cardiopulmonary exercise testing), were not consistently available due to the retrospective design and extensive study duration. Future prospective studies should incorporate these parameters to enhance risk stratification and clinical management.
Conclusion
This retrospective cohort study indicates a reduction in overall mortality among obstetric patients with pulmonary hypertension compared to previously reported data. Although the mean hospital length of stay was approximately two times longer than that observed following an uncomplicated cesarean delivery, overall mortality in our cohort was 3%. We demonstrate that elevated pulmonary artery pressure, but not OB-CMI score, is significantly associated with ICU admission and prolonged hospitalization in pregnant patients with pulmonary hypertension. These findings suggest that current general obstetric scoring tools may be inadequate for risk stratification in this specialized population. Given the rarity of this condition, further studies with larger patient cohorts are necessary to refine risk stratification and generate recommendations about management in this high-risk patient group.
Supplementary Material
HIGHLIGHTS.
Question:
This study examined whether the outcomes of pregnant patients with pulmonary hypertension are influenced by clinical covariates.
Finding:
Only pulmonary hypertension severity, not comorbidity scores, was associated with longer stays and more ICU admissions.
Meaning:
Current risk scores may not fully reflect the risks for pregnant patients with pulmonary hypertension.
Funding Statement
KJG reports funding from NIH/NHLBI grants K08 HL146963, K08 HL146963-02S1, and R03 HL162756. VPK reports funding from the NIH/NHLBI grants K08HL161326-01A1, Anesthesia Patient Safety Foundation (APSF), and BWH IGNITE Award.
Glossary of Abbreviations
- WHO
World Health Organization
- OB-CMI
Obstetric Comorbidity Index
- ICU
Intensive Care Unit
- MGB
Massachusetts General Brigham
- TMC
Tufts Medical Center
- PASP
Pulmonary artery systolic pressure
- ECMO
Extracorporeal Membrane Oxygenation
Footnotes
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Presentation at Meetings
Presented in part at the 2024 Annual Meeting of the Society for Obstetric Anesthesia and Perinatology
Declaration of Interest
KJG has served as a consultant to Aetion, Roche, BillionToOne, and Janssen Global outside the scope of the submitted work. VPK reports consulting fees from Avania CRO unrelated to the current work. VPK reports patent #WO2021119593A1 for the control of a therapeutic delivery system assigned to Mass General Brigham. All other authors: none.
References
- 1.Hoeper MM, Bogaard HJ, Condliffe R, et al. Definitions and diagnosis of pulmonary hypertension. J Am Coll Cardiol. Dec 24 2013;62(25 Suppl):D42–50. doi: 10.1016/j.jacc.2013.10.032 [DOI] [PubMed] [Google Scholar]
- 2.Association PH. Types of Pulmonary Hypertension. 2020;
- 3.Dai LL, Jiang TC, Li PF, et al. Predictors of Maternal Death Among Women With Pulmonary Hypertension in China From 2012 to 2020: A Retrospective Single-Center Study. Front Cardiovasc Med. 2022;9:814557. doi: 10.3389/fcvm.2022.814557 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Low TT, Guron N, Ducas R, et al. Pulmonary arterial hypertension in pregnancy-a systematic review of outcomes in the modern era. Pulm Circ. Apr-Jun 2021;11(2):20458940211013671. doi: 10.1177/20458940211013671 [DOI] [Google Scholar]
- 5.Meng ML, Landau R, Viktorsdottir O, et al. Pulmonary Hypertension in Pregnancy: A Report of 49 Cases at Four Tertiary North American Sites. Obstet Gynecol. Mar 2017;129(3):511–520. doi: 10.1097/aog.0000000000001896 [DOI] [PubMed] [Google Scholar]
- 6.Weiss BM, Zemp L, Seifert B, Hess OM. Outcome of pulmonary vascular disease in pregnancy: a systematic overview from 1978 through 1996. J Am Coll Cardiol. Jun 1998;31(7):1650–7. doi: 10.1016/s0735-1097(98)00162-4 [DOI] [PubMed] [Google Scholar]
- 7.Thomas E, Yang J, Xu J, Lima FV, Stergiopoulos K. Pulmonary Hypertension and Pregnancy Outcomes: Insights From the National Inpatient Sample. J Am Heart Assoc. Oct 24 2017;6(10)doi: 10.1161/jaha.117.006144 [DOI] [Google Scholar]
- 8.Horon I Characteristics of Mothers Admitted to Intensive Care Units During Hospitalization for Delivery of a Live-born Infant: United States, 2020–2022. NCHS Data Brief. Dec 2023;(485):1–7. [Google Scholar]
- 9.Hemnes AR, Kiely DG, Cockrill BA, et al. Statement on pregnancy in pulmonary hypertension from the Pulmonary Vascular Research Institute. Pulm Circ. Sep 2015;5(3):435–65. doi: 10.1086/682230 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Olsson KM, Channick R. Pregnancy in pulmonary arterial hypertension. Eur Respir Rev. Dec 2016;25(142):431–437. doi: 10.1183/16000617.0079-2016 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Krishnan S, Fricke E, Córdoba Muñoz M, Chalifoux L, Girgis R. Pulmonary Hypertension Complicating Pregnancy. Current Pulmonology Reports. April/21 2021;10 doi: 10.1007/s13665-021-00275-1 [DOI] [Google Scholar]
- 12.Sliwa K, van Hagen IM, Budts W, et al. Pulmonary hypertension and pregnancy outcomes: data from the Registry Of Pregnancy and Cardiac Disease (ROPAC) of the European Society of Cardiology. Eur J Heart Fail. Sep 2016;18(9):1119–28. doi: 10.1002/ejhf.594 [DOI] [PubMed] [Google Scholar]
- 13.Sun X, Feng J, Shi J. Pregnancy and pulmonary hypertension: An exploratory analysis of risk factors and outcomes. Medicine (Baltimore). Nov 2018;97(44):e13035. doi: 10.1097/md.0000000000013035 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Jha N, Jha AK, Mishra SK, Sagili H. Pulmonary hypertension and pregnancy outcomes: Systematic Review and Meta-analysis. Eur J Obstet Gynecol Reprod Biol. Oct 2020;253:108–116. doi: 10.1016/j.ejogrb.2020.08.028 [DOI] [PubMed] [Google Scholar]
- 15.Yang JZ, Fernandes TM, Kim NH, et al. Pregnancy and pulmonary arterial hypertension: a case series and literature review. Am J Obstet Gynecol MFM. Jul 2021;3(4):100358. doi: 10.1016/j.ajogmf.2021.100358 [DOI] [PubMed] [Google Scholar]
- 16.Kang M, Hart CM, Kempker JA, Veeraraghavan S, Trammell AW. Pulmonary hypertension mortality trends in United States 1999–2019. Ann Epidemiol. Nov 2022;75:47–52. doi: 10.1016/j.annepidem.2022.09.001 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Easter SR, Bateman BT, Sweeney VH, et al. A comorbidity-based screening tool to predict severe maternal morbidity at the time of delivery. Am J Obstet Gynecol. Sep 2019;221(3):271.e1–271.e10. doi: 10.1016/j.ajog.2019.06.025 [DOI] [Google Scholar]
- 18.Bateman BT, Mhyre JM, Hernandez-Diaz S, et al. Development of a comorbidity index for use in obstetric patients. Obstet Gynecol. Nov 2013;122(5):957–965. doi: 10.1097/AOG.0b013e3182a603bb [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Metcalfe A, Lix LM, Johnson JA, et al. Validation of an obstetric comorbidity index in an external population. Bjog. Dec 2015;122(13):1748–55. doi: 10.1111/1471-0528.13254 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Kern-Goldberger AR, Srinivas SK, Harhay MO, Levine LD. External Validation of the Clinical Obstetric Comorbidity Index across a Diverse Health System. Am J Perinatol. May 6 2025;doi: 10.1055/a-2572-1727 [DOI] [Google Scholar]
- 21.Lafitte S, Pillois X, Reant P, et al. Estimation of pulmonary pressures and diagnosis of pulmonary hypertension by Doppler echocardiography: a retrospective comparison of routine echocardiography and invasive hemodynamics. J Am Soc Echocardiogr. May 2013;26(5):457–63. doi: 10.1016/j.echo.2013.02.002 [DOI] [PubMed] [Google Scholar]
- 22.Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Respir J. Jan 2023;61(1)doi: 10.1183/13993003.00879-2022 [DOI] [Google Scholar]
- 23.Ma R, Gao H, Cui J, et al. Pregnancy feasibility in women with mild pulmonary arterial hypertension: a systematic review and meta-analysis. BMC Pregnancy Childbirth. Jun 8 2023;23(1):427. doi: 10.1186/s12884-023-05752-w [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Aoyama K, D’Souza R, Inada E, Lapinsky SE, Fowler RA. Measurement properties of comorbidity indices in maternal health research: a systematic review. BMC Pregnancy Childbirth. Nov 13 2017;17(1):372. doi: 10.1186/s12884-017-1558-3 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Aoyama K, D’Souza R, Pinto R, et al. Risk prediction models for maternal mortality: A systematic review and meta-analysis. PLoS One. 2018;13(12):e0208563. doi: 10.1371/journal.pone.0208563 [DOI] [PMC free article] [PubMed] [Google Scholar]
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