To study the birth rate, mortality, complications, related factors of preterm infants at Beijing Haidian Maternity and Children's Hospital in 2007, so as to establish the foundations for a more systematic and effective program for clinical treatments. Data of all the neonates born at Beijing Haidian Maternity and Children's Hospital during the period from January 1, 2007 to December 31, 2007 were recorded for statistical analysis. All near-term infants of 35 - 37 weeks of gestational age were taken into observation group. Within 24 hours after birth, blood routine examination, urine and stool routine examination, blood gas analysis and electrolytes, blood glucose monitoring (at 1st, 3rd, 6th, 12th, and 24th hours), chest radiography examination, skull and heart color Doppler ultrasonographic examination were conducted. Full-term infants who were born on the first day of every month were randomly selected as a comparison group (totally 350 cases) for statistical analysis. Complications of the two groups were recorded in detail. Factors such as the ages of parturients, maternal infections, pregnancy-induced hypertension, diabetes, anaemia, premature rupture of membranes, abnormal aminotic fluid, abnormal umbilical cord, abnormal placenta, and twin were analyzed and compared. Of the 12,286 infants born during the study period, 333 were late-preterm infants; the birth rate of late-preterm infants was 2.71%. Among the complications in late-preterm infants, the hyperbilirubinemia topped at 33.6%, followed by respiratory distress (16.8%), hypoglycemia (9.0%), intracranial hemorrhage (8.1%), anemia or erythrocytosis (5.7%), and digestive system disease (5.4%). Late-preterm infants have higher rate of the hyperbilirubinemia, respiratory distress, hypoglycemia, anemia or erythrocytosis and digestive system disease (P < 0.05). The length of hospital stay of late-preterm infants, which is 5.1 d +/- 3.90 d, was significantly longer than those of full-term infants which was 3.2 d +/- 1.61 d (P < 0.05). The proportion of late-preterm infants was 2.71% of all live born infants at Beijing Haidian Maternity and Children's Hospital from January 1, 2007 to December 31, 2007. The occurrence rate of complications and mortality rate were higher than those of full-term infants. Late-preterm infants also have longer hospital stay. Hyperbilirubinemia is a common complication for late-preterm infants. Pregnancy-induced hypertension, anemia, premature rupture of membranes and twins are the major causes of higher morbidity and mortality of late-preterm infants. Pediatricians should pay much more attention to late-preterm infants, and should accept them for further observation and treatments.