In an otherwise healthy newborn, the cause of PPHN is often unknown. However, the following are believed to be possible causes of PPHN.

1. Stress while the baby is in the uterus (associated with certain pregnancy complications, such as maternal diabetes, high blood pressure or anemia, or delivery after 40 weeks) may increase the risk.

2. Meconium aspiration syndrome, anemia, severe pneumonia, infection, hypoglycemia (low blood sugar), and birth asphyxia (when the baby is deprived of oxygen during a complicated delivery) have all been associated with PPHN.

3. SSRIs or selective serotonin reuptake inhibitors antidepressants such as citalopram, fluoxetine, paroxetine and sertraline sold under 19 brand names, including Celexa, Prozac, Paxil and Zoloft. Normally, the lung disorder is rare, with one to two per 1,000 births. But when pregnant women took the drugs in question after the 20th week of pregnancy, the incidence rose to six to 12 per 1,000 births. See Full Report

These conditions or antidepressants may cause the pressure in the blood vessels leading to the lungs to increase to the point where the baby's blood continues to bypass the lungs after birth, resulting in PPHN. These conditions are often temporary and reversible, with intensive care and time for the lungs and body to heal.

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