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Rationale: Few studies have identified risk sets for perinatal factors and airflow obstruction into middle adulthood.

Objectives: To investigate associations between gestational age (GA), GA-adjusted birthweight, and mode of delivery and persistent airflow obstruction among patients 7-49 years old with obstructive lung diseases.

Methods: The study population encompassed 44,778 individuals with asthma or chronic obstructive pulmonary disease (COPD) and one or more registration of post-bronchodilator values of forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) recorded in the Swedish National Airway Register in 2014-2022 and with both GA and birthweight data in the Medical Birth Register between 1973-2015. Persistent airflow obstruction was defined as a FEV1/FVC z-score below the lower limit of normal. Analyses were done separately for children, young adults, and middle-aged adults.

Results: Subjects who were extremely, very, moderate, and late preterm-born all had increased odds ratios (ORs) of persistent airflow obstruction up to age 49 years compared with those term-born. Middle-aged adults born small for GA had increased OR of persistent airflow obstruction compared with those appropriate for GA (OR, 1.49; 95% confidence interval, 1.23-1.81). In the risk sets, GA was the most significant covariate for persistent airflow obstruction. GA-adjusted birthweight was an additional covariate for those born late preterm, term, or postterm. Mode of delivery did not contribute.

Conclusions: GA was an independent covariate of persistent airflow obstruction and, in the risk sets, proved to be the most important covariate in patients of all ages with either asthma or COPD. GA-adjusted birthweight further improved the prediction.