The arterial duct is located between the beginning of the descending aorta and the opening of the left pulmonary artery, and is a physiological channel for guiding pulmonary artery blood flow into the descending aorta in the fetal circulation. During fetal life, all alveoli are atrophied, there is no respiratory activity, pulmonary vascular resistance is high, the right ventricle discharges blood, most of which flows into the descending aorta via the arterial duct to supply the lower half of the fetus, and some of the blood reaches the placenta via the umbilical artery, where it is metabolically exchanged with maternal blood in the embryonic placenta and then incorporated into the umbilical vein to return to the fetal blood circulation. After birth, the oxygen saturation rises, the smooth muscle of the middle layer of the ductus arteriosus contracts and closes functionally within 10 to 15 hours, but there are cases of late closure. The ductus arteriosus gradually closes anatomically around 3 months after birth to become the arterial ligament; if it does not close, it is called an unclosed ductus arteriosus. The fetal ductus arteriosus develops from the dorsal aspect of the sixth aortic gill arch, and its morphology varies from person to person in terms of length, straightness or tortuosity, as long as the blood flow can pass smoothly into the descending aorta, it is not a pathological condition and should not be induced as a malformation. All 15 fetuses with tortuous arterial ducts were born successfully and had no adverse records of physical health after birth. Health care measures: 1. No special treatment and health care is needed during the fetal period; 2. Normal delivery can be awaited without special delivery measures; 3. Cardiac ultrasonography is performed after birth. Treatment: No treatment is required. Long-term prognosis: Fully normal life, study and work.