Functional closure of the ductus arteriosus occurs within 10 to 15 hours after birth by constriction of the medial smooth muscle in the ductus. Anatomic closure is completed by 2 to 3 weeks of age by permanent changes in the endothelium and subintimal layers of the ductus.
Oxygen, prostaglandin E2 (PGE2) levels, and maturity of the newborn are important factors in closure of the ductus. Acetylcholine and bradykinin also constrict the ductus.