[Serum level of digoxin-like immunoreactive substances in newborn infants in the first two weeks of life, in umbilical cord blood and in pregnant patients at the time of labor].

A digoxin-like immunoreactivity (DLIS) was measured by two routinely used clinical digoxin-immunoassays (radio- and enzymeimmunoassay) in cord blood of 255 newborns, in sera of their mothers at birth and in sera of 211 newborns during the first two postpartal weeks. The highest DLIS levels were found in serum of neonates at the first day of life (median: 0.23 ng/ml, 25% and 75% percentile: 0.19 and 0.28 ng/ml) and in cord blood (median: 0.21 ng/ml, 25% and 75% percentile: 0.19 and 0.24 ng/ml); maternal serum was shown to have three times less DLIS (median: 0.08 ng/ml, 25% and 75% percentile: 0.05 and 0.10 ng/ml). There was no significant correlation between DLIS concentrations in serum of newborns, cord blood or pregnants. The DLIS serum levels of preterms with birthweight less than 2500 g and gestational age less than 37 weeks were significantly lower than those of normal neonates at term (p less than 0.01); concomitantly the lowest DLIS levels were found in maternal serum of preterms (p less than 0.01). These observations strongly suggest rather a DLIS origin in the newborn than in the mother. During the first two postpartal weeks the DLIS concentration of a vast majority of the 211 newborns (91%) decreased continuously to one half of the starting value. Within the second postpartal week preterms were found to have a significantly delayed decrease in the DLIS serum levels (p less than 0.01). Small for date newborns showed no difference in their postpartal DLIS time course compared to normal neonates.(ABSTRACT TRUNCATED AT 250 WORDS)