Naumburg E, et al. - In this population-based registry study involving 128 cases and 768 controls, researchers evaluated the risk of pulmonary hypertension (PAH) following exposure to premature birth and other factors in the decades when modern neonatal care was introduced and survival rates increased. From population-based governmental and national quality registers, information on PAH and perinatal factors were retrieved. Cases were adults and children over the age of five with PAH born from 1973 to 2010 and matched by birth year and delivery hospital individually to six controls. Investigators found that preterm birth was over three times more common among cases than among controls. Maternal hypertension, several neonatal risk factors and female gender were associated with PAH independently when considering potential confounders. Preterm birth, together with other factors, contributes significantly to PAH. Over the last few decades, PAH after a premature birth has increased. The research shows that new, yet unknown variables may play a part in the risk of preterm-born infants developing PAH later in life.