Risk factors and outcomes of preterm birth. A study of the associations of preterm birth with cerebral palsy and atopic diseases

Background: Children born preterm are at increased risk for a number of chronic diseases, including cerebral palsy and asthma. Asthma is usually categorised among the atopic diseases, but whether preterm birth also affects the risk for other atopic diseases, is less explored. Furthermore, it is known that women with asthma are at increased risk of too early delivery, but the knowledge on risk of preterm birth for mothers with atopic dermatitis or allergic rhinoconjunctivitis is limited. Preterm birth may be caused by interactions between disorders of pregnancy and conditions related to mother and fetus. Whether these pathologic conditions influence the risk of later chronic diseases for preterm children, is still largely unknown. Objectives: We wanted to assess how preterm birth and pregnancy disorders relate to risk of cerebral palsy and severe asthma and atopic dermatitis. In addition, we aimed to explore the risk of preterm birth with maternal atopic diseases. Methods: Prospective national cohort studies were performed by linking data from the Medical Birth Registry of Norway to other compulsory national registries. Results: Preterm birth and several pregnancy disorders were strongly associated with cerebral palsy. Preterm birth was associated with increased risk of severe asthma and decreased risk of severe atopic dermatitis. The two diseases were differently related to pregnancy disorders and other risk factors. Maternal asthma was associated with increased risk of preterm birth, but maternal atopic dermatitis and allergic rhinoconjunctivitis were associated with decreased risk. Conclusions: Risk of cerebral palsy with or without a recorded pregnancy disorder varied within categories of gestational age. Our findings suggest a protective effect of preterm birth on atopic dermatitis and a reduced risk of preterm delivery for mothers with other atopic diseases than asthma. This may shed light on mechanisms of preterm birth, but further studies are needed to confirm and explore these findings