[The fibronectin deficiency in normal newborn infants corrects itself very quickly]

Fibronectin (FN) is a protein which acts as an opsonin and participates in anti-infective mechanisms. We measured FN in cord blood from 39 normal newborns by Laurell's electroimmunoassay. The mean value of FN was 13.5 +/- 6.8 mg/dl, lesser then mean value of 26 normal children 1 mo. to 7 y. old, 27.3 +/- 8.7 mg/dl (p less than 0.001). FN continued being low, 14.1 +/- 8.1 mg/dl al 48 h. of age. Nevertheless it was normal at 15 days of age (24.6 +/- 9.7 mg/dl). FN levels were lower at 15 days of age in 19 newborns who received vitamin K (12.2 +/- 6.1 mg/dl) than in the group which was not treated (18.1 +/- 9.9 mg/dl) but the difference was not significant (p greater than 0.05). There was a close correlation between cord blood levels and levels at 48 h. (p = 0.001) and levels at 15 d. (p = 0.003). There was no relationship either with the gestational age and birth weight, no prothrombin and protein C levels. The FN decrease in the newborn can be one of the causes of the opsonization deficiency, nevertheless normalization occurred very soon, before the second week.