Neonatology

Measuring Progress: How BPD is Diagnosed and Graded

At a Glance

Bronchopulmonary Dysplasia (BPD) is formally diagnosed and graded when a premature baby reaches 36 weeks postmenstrual age. Doctors use the Jensen criteria to grade BPD severity from 1 to 3 based purely on the type of breathing support the baby requires at that milestone.

As your baby approaches their original due date, the medical team uses specific milestones to assess how their lungs are healing and growing. The most important milestone is 36 weeks postmenstrual age (PMA)—the point at which your baby would have been 36 weeks along in the pregnancy ^[1]^[2].

The 36-Week Milestone

At 36 weeks PMA, your baby’s lungs have had time to adapt to life outside the womb. This is the standard time doctors use to formally diagnose and “grade” the severity of Bronchopulmonary Dysplasia (BPD) ^[3]^[4]. While this milestone is a “snapshot” in time, it helps the team predict what kind of support your baby might need as they grow ^[3]^[5].

Grading BPD: The Jensen 2019 Criteria

In the past, BPD was graded simply by how much oxygen a baby needed. However, modern medicine increasingly uses the Jensen 2019 criteria (also known as the BPD Collaborative classification). To reduce confusion and subjectivity, this system categorizes severity based purely on the type of breathing machine or support your baby requires at 36 weeks, rather than the exact oxygen percentage ^[3]^[6].

Severity Grade	Type of Support at 36 Weeks PMA
Grade 1	Nasal cannula with a flow rate of $\le$ 2 liters per minute (L/min) ^[3].
Grade 2	Nasal cannula with a flow rate > 2 L/min, OR non-invasive positive pressure support (like CPAP, NIPPV, or BiPAP) ^[3].
Grade 3	Invasive mechanical ventilation (a breathing tube) ^[3].

Knowing your baby’s grade is helpful because it guides the medical team in anticipating future needs, such as home oxygen or specialized follow-up care ^[3]^[7].

The Oxygen Reduction Test

Sometimes, a baby may be receiving a small amount of extra oxygen “just in case,” but their body might be ready to breathe room air. To confirm if a baby truly has BPD, doctors may perform an oxygen reduction test (also called a room air challenge) ^[8]^[9].

During this test, the medical team slowly lowers the baby’s supplemental oxygen while closely monitoring their oxygen saturation (SpO2)—the amount of oxygen in their blood ^[8]^[9]. If the baby can maintain an SpO2 of 90% or higher while breathing normal room air (21% oxygen), they “pass” the test ^[2]^[8]. If their levels drop, it confirms they still need help and meet the “physiologic definition” of BPD ^[2].

What is Happening Inside the Lungs?

BPD isn’t just about “weak” breathing; it’s about a change in the lung’s architecture. There are two main biological hurdles in BPD:

Reduced Gas Exchange Surface Area: Because lung development was interrupted, the lungs have fewer alveoli (air sacs). Instead of many tiny sacs, there are fewer, larger ones. This means there is less total surface area for oxygen to move from the air into the blood ^[10]^[11].
Impaired Vascular Development: The tiny blood vessels (capillaries) that wrap around the air sacs also stop growing properly. This is called impaired angiogenesis ^[12]^[13]. When these blood vessels are sparse or simplified, it is harder for the heart to pump blood through the lungs, which can sometimes lead to high blood pressure in the lung’s arteries (pulmonary hypertension) ^[14]^[15].

Understanding these grades and biological changes can help you have more detailed conversations with your baby’s care team about their progress and path forward.

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Common questions in this guide

When is a baby officially diagnosed with BPD?

Doctors formally diagnose and grade the severity of Bronchopulmonary Dysplasia when a premature baby reaches 36 weeks postmenstrual age. This milestone allows the lungs time to adapt to life outside the womb and helps predict future respiratory support needs.

What are the Jensen criteria for grading BPD?

The Jensen criteria categorize BPD severity into three grades based on the type of breathing support a baby needs at 36 weeks. Grade 1 requires a low-flow nasal cannula, Grade 2 requires a high-flow cannula or non-invasive pressure like CPAP, and Grade 3 requires a breathing tube.

What is an oxygen reduction test for premature babies?

An oxygen reduction test, or room air challenge, involves slowly lowering a baby's supplemental oxygen to see if they can breathe normal room air. If their blood oxygen levels stay at 90% or higher, they pass, but if levels drop, it confirms they still need respiratory support.

How does BPD change the development of a baby's lungs?

BPD interrupts normal lung development, resulting in fewer, larger air sacs instead of many tiny ones, which reduces the surface area for getting oxygen into the blood. It also impairs the growth of tiny blood vessels, which can lead to high blood pressure in the lungs.

Curated prompts to bring to your next appointment.

1.According to the Jensen criteria, what Grade is my baby's BPD, and what does that mean for their long-term recovery?
2.Why is 36 weeks PMA the standard time for this diagnosis, and will we re-evaluate their lungs again at 40 weeks?
3.Is my baby a candidate for an oxygen reduction test or 'room air challenge' right now?
4.Based on my baby's current support needs, how much 'gas exchange surface area' do you estimate their lungs currently have?
5.How is the development of the blood vessels in my baby's lungs being monitored to check for things like pulmonary hypertension?

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References (15)

1
The Diagnosis of Bronchopulmonary Dysplasia in Very Preterm Infants. An Evidence-based Approach.
Jensen EA, Dysart K, Gantz MG, et al.
American journal of respiratory and critical care medicine 2019; (200(6)):751-759 doi:10.1164/rccm.201812-2348OC.
PMID: 30995069
2
Simplified bedside assessment of pulmonary gas exchange in very preterm infants at 36 weeks' postmenstrual age.
Stoecklin B, Choi YJ, Rakshasbhuvankar A, et al.
Thorax 2021; (76(7)):689-695 doi:10.1136/thoraxjnl-2020-214659.
PMID: 33574124
3
Severity of Bronchopulmonary Dysplasia Among Very Preterm Infants in the United States.
Jensen EA, Edwards EM, Greenberg LT, et al.
Pediatrics 2021; (148(1)) doi:10.1542/peds.2020-030007.
PMID: 34078747
4
Scoping review shows wide variation in the definitions of bronchopulmonary dysplasia in preterm infants and calls for a consensus.
Hines D, Modi N, Lee SK, et al.
Acta paediatrica (Oslo, Norway : 1992) 2017; (106(3)):366-374 doi:10.1111/apa.13672.
PMID: 27862302
5
Pulmonary function and bronchopulmonary dysplasia classification: insights from the Spanish Registry.
Ramos-Navarro C, Sánchez-Luna M, Pérez-Tarazona S, et al.
European journal of pediatrics 2024; (183(9)):3757-3766 doi:10.1007/s00431-024-05629-w.
PMID: 38858227
6
Newer bronchopulmonary dysplasia definitions and prediction of health economics impacts in very preterm infants.
Kurihara C, Zhang L, Mikhael M
Pediatric pulmonology 2021; (56(2)):409-417 doi:10.1002/ppul.25172.
PMID: 33200543
7
Long-term lung function follow-up of preterm infants less than 32 weeks of gestational age.
Merino-Hernández A, Muñoz-Cutillas A, Ramos-Navarro C, et al.
Pediatric pulmonology 2024; (59(11)):2922-2931 doi:10.1002/ppul.27158.
PMID: 38958223
8
Room air challenge predicts duration of supplemental respiratory support for infants with bronchopulmonary dysplasia.
Arora P, Dahlgren A, Dawson S, et al.
Journal of perinatology : official journal of the California Perinatal Association 2021; (41(4)):772-778 doi:10.1038/s41372-021-00958-2.
PMID: 33589726
9
Weaning oxygen in infants with bronchopulmonary dysplasia.
Everitt LH, Awoseyila A, Bhatt JM, et al.
Paediatric respiratory reviews 2021; (39()):82-89 doi:10.1016/j.prrv.2020.10.005.
PMID: 33309219
10
Bronchopulmonary dysplasia.
Thébaud B, Goss KN, Laughon M, et al.
Nature reviews. Disease primers 2019; (5(1)):78 doi:10.1038/s41572-019-0127-7.
PMID: 31727986
11
Short- and Long-Term Complications of Bronchopulmonary Dysplasia.
Homan TD, Nayak RP
Respiratory care 2021; (66(10)):1618-1629 doi:10.4187/respcare.08401.
PMID: 34552015
12
Research progress of microvascular development in bronchopulmonary dysplasia.
Zhang J, Du W, Zhang Z, et al.
Pediatric investigation 2024; (8(4)):299-312 doi:10.1002/ped4.12441.
PMID: 39720284
13
Involvement of Hdac3-mediated inhibition of microRNA cluster 17-92 in bronchopulmonary dysplasia development.
Wang D, Hong H, Li XX, et al.
Molecular medicine (Cambridge, Mass.) 2020; (26(1)):99 doi:10.1186/s10020-020-00237-4.
PMID: 33143661
14
Signaling Pathways Involved in the Development of Bronchopulmonary Dysplasia and Pulmonary Hypertension.
Mathew R
Children (Basel, Switzerland) 2020; (7(8)) doi:10.3390/children7080100.
PMID: 32824651
15
Role of left atrial hypertension in pulmonary hypertension associated with bronchopulmonary dysplasia.
Sullivan RT, Tandel MD, Bhombal S, et al.
Frontiers in pediatrics 2022; (10()):1012136 doi:10.3389/fped.2022.1012136.
PMID: 36313896

This page explains how Bronchopulmonary Dysplasia (BPD) is diagnosed and graded for educational purposes. Always consult your neonatologist or pediatrician regarding your baby's specific diagnosis and respiratory needs.

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