Perform bedside echocardiography on neonates (term and preterm infants) who were admitted to our neonatal department within 24 hours of birth, and establish a geometric reference range of neonatal cardiac ultrasound and explore the hemodynamic changes of early newborns.

Bedside echocardiography were performed to measure the diameter of each heart cavity and large vessels, velocity of each valve and aorta, wall thickness, left ventricular systolic function, right heart Tei index, Tricuspid Annular Plane Systolic Excursion(TPASE) of term and preterm infants respectively on 0 day, 3d, 7d of life and postmenstrual age of 30 weeks, 32 weeks, 34 weeks and 36 weeks.

Inclusion Criteria:

• 1. Infants with normal hearts (infants with small patent fora-men oval or small patent ductus arteriosus were not excluded).

  2.Healthy preterm infant with no evidence of sepsis, renal failure. 3. Absence of other major congenital anomalies or syndromes 4. Prior written consent was obtained from the parents.

Exclusion Criteria:

• Infants with severe congenital malformations, either cardiac or non-cardiac.

Babies born in the obstetrics department of Peking University Third Hospital and admitted to the neonatal ward.