Surfactant protein D levels in umbilical cord blood and capillary blood of premature infants. The influence of perinatal factors.

Surfactant protein D (SP-D) is a collectin that plays an important role in the innate immune system and takes part in the surfactant homeostasis by regulating the surfactant pool size. The aims of this study were to investigate the values of SP-D in umbilical cord blood and capillary blood of premature infants and to relate the levels to perinatal conditions. A total of 254 premature infants were enrolled in the present study. Umbilical cord blood was drawn at the time of birth and capillary blood at regular intervals throughout the admission. The concentration of SP-D in umbilical cord blood and capillary blood was measured using ELISA technique. The median concentration of SP-D in umbilical cord blood was twice as high as in mature infants, 769 ng/mL (range 140-2,551), with lowest values in infants with intrauterine growth retardation (IUGR) and rupture of membranes (ROM). The median concentration of SP-D in capillary blood day 1 was 1,466 ng/mL (range 410-5,051 ng/mL), with lowest values in infants born with ROM and delivered vaginally. High SP-D levels in umbilical cord blood and capillary blood on day 1 were found to be more likely in infants in need for respiratory support or surfactant treatment and susceptibility to infections. We conclude that SP-D concentrations in umbilical cord blood and capillary blood in premature infants are twice as high as in mature infants and depend on several perinatal conditions. High SP-D levels in umbilical cord blood and capillary blood on day 1 were found to be related to increased risk of RDS and infections.