A population-based cohort study from the Nordic countries has found that women who take SSRIs during the second half of pregnancy are more than twice as likely to give birth to children with persistent pulmonary hypertension of the newborn (PPHN). However, the absolute risk remains very low. Data were obtained from national registers of births, deaths and dispensed prescriptions. Exclusion criteria were multiple births and a gestational age of less than 33 weeks. More than 1.6 million infants, born between 1996 and 2007, were included in the study.