Perinatal changes in size of the fetal great arteries

Background and Objectives: At birth, the fetal circulation must immediately adapt to extrauterine life. Our goal was to evaluate perinatal changes in the size of the aorta (Ao) and pulmonary artery (PA), and to investigate factors influencing these changes. Subjects and Methods: Aortic and PA diameters were measured by echocardiography in 50 healthy term babies one day before and 4 to 5 days after birth. Results: Compared with prenatal measurements, the Ao increased (from 7.4±0.6 mm to 8.4±0.6 mm, p<0.01) and the PA decreased (from 9.5 ±0.8 mm to 8.7±0.8 mm, p<0.01) in size after birth. The Ao/PA ratio increased from 0.78±0.07 before birth to 0.97±0.08 after birth (p<0.01), but there was no significant difference in the sum of the diameters of the great arteries between pre- and postnatal measurements. Postnatal increases in aortic size correlated negatively with prenatal aortic diameter (r=-0.37, p<0.05), but was not related to body weight. According to multiple regression analysis, significant variables for predicting perinatal changes in size of the Ao and PA were the prenatal Ao/PA ratio and the prenatal PA diameter, respectively. Conclusion: Despite a difference existing in prenatal diameters between Ao and PA, circulatory changes at birth make the great artery sizes equal, and do so regardless of body weight.