# The Incidence of Pulmonary Hypertension and the Association with Bronchopulmonary Dysplasia in Preterm Infants of Extremely Low Gestational Age: Single Centre Study at the Maternity Hospital of University Medical Centre Ljubljana, Slovenia

## TL;DR

This study found that pulmonary hypertension in extremely preterm infants may not be detectable by early echocardiography and can develop later, even after NICU discharge.

## Contribution

The study highlights the limitations of current screening timelines for pulmonary hypertension in preterm infants with bronchopulmonary dysplasia.

## Key findings

- Echocardiographic screening at day 7 and at NICU discharge failed to detect pulmonary hypertension in most cases.
- Most cases of pulmonary hypertension were identified clinically or via echocardiography before day 7.
- One case of pulmonary hypertension was detected at 38 weeks postmenstrual age, suggesting later screening may be necessary.

## Abstract

What are the main findings?
•In the first few days of life, preterm infants with a high clinical probability of pulmonary hypertension (PH) may not yet show echocardiographic signs of PH.•In preterm infants with bronchopulmonary dysplasia (BPD), late screening prior to NICU discharge (≤36 weeks PMA) may still be too early to detect PH that develops later in the course of BPD.

In the first few days of life, preterm infants with a high clinical probability of pulmonary hypertension (PH) may not yet show echocardiographic signs of PH.

In preterm infants with bronchopulmonary dysplasia (BPD), late screening prior to NICU discharge (≤36 weeks PMA) may still be too early to detect PH that develops later in the course of BPD.

What is the implication of the main finding?
•When there is a clear clinical indication, the absence of echocardiographic signs of PH should not be a contraindication to starting inhaled nitric oxide (iNO) or a reason to delay treatment.•Echocardiographic screening for PH should be considered beyond the neonatal period and after NICU discharge.

When there is a clear clinical indication, the absence of echocardiographic signs of PH should not be a contraindication to starting inhaled nitric oxide (iNO) or a reason to delay treatment.

Echocardiographic screening for PH should be considered beyond the neonatal period and after NICU discharge.

Background: Pulmonary hypertension (PH) occurs in ~25% of infants with moderate-to-severe bronchopulmonary dysplasia (BPD) and is associated with substantial morbidity and mortality. The American Heart Association and American Thoracic Society recommend routine echocardiographic screening for PH in preterm infants with BPD at 36 weeks’ postmenstrual age (PMA), yet the true incidence remains unclear owing to non-uniform diagnostic criteria. Emerging evidence suggests a potential role for earlier screening. Objectives: (i) to determine the incidence of pulmonary hypertension (PH) and bronchopulmonary dysplasia (BPD) in preterm infants of extremely low gestational age; (ii) to determine the incidence of PH among infants diagnosed with BPD (BPD-PH); and (iii) to evaluate the utility of early screening at 7 days of life and late screening at discharge in relation to subsequent BPD. Methods: We conducted a prospective cohort study of all infants born at 22 + 0 to 28 + 6 weeks’ gestation and admitted to our tertiary NICU between 1 September 2022 and 31 December 2024. Clinical and echocardiographic assessments for PH and BPD were performed by neonatologists trained in neonatal echocardiography. Results: Seventy-eight infants born at 22 + 0–28 + 6 weeks’ gestation were enrolled; 71 underwent early screening and 57 underwent late screening. Early echocardiography at day 7 and late screening at discharge identified no cases of PH. PH was diagnosed clinically and/or echocardiographically in 10 infants before day 7 and in one infant at 38 weeks’ PMA. BPD developed in 42 of 57 infants (73.7%). Conclusions: In this cohort of extremely low-gestational-age infants, echocardiographic screening performed by neonatologists detected no PH at day 7 and only one case at late screening (at 38 weeks’ PMA/before discharge). Most PH was identified prior to day 7 on clinical and/or echocardiographic grounds.