FOETAL DEVELOPMENT OF SERUM LEVELS OF IGG AND IGM

The serum concentrations of the immunoglobulins G and M were studied in non‐viable foetuses with gestational ages of 13–26 weeks, and also in premature, mature and postmature infants. Among the prematurely born infants there was an overrepresentation of infants with very low gestational ages. The serum IgG concentrations in the mothers at the time of abortion or delivery were also studied. In full‐term infants there was a systematic difference between simultaneously taken capillary and umbilical cord samples, with higher serum concentrations of IgG in the former. For this reason umbilical cord sera were used throughout in this study. The maternal serum concentration of IgG was found to be of some importance for the foetal IgG level. The foetal: maternal IgG ratio increased, as also did the foetal IgG concentration, exponentially during pregnancy, with the exception of its last weeks when the development took place relatively more slowly. IgM in serum was observed (>1 mg/100 ml) in two foetuses with gestational ages as short as 14 and 16 weeks. From the 24th week of pregnancy onwards, IgM was found in the serum in practically all cases. From about the 29th‐30th week of pregnancy, no significant increase in the serum IgM with increasing gestational age was observed in the infants studied. Copyright © 1969, Wiley Blackwell. All rights reserved