[Mother-child transmission of immunoglobulins G].

The placental transfer of immunoglobulins is made by active transport and only IgG class of immunoglobulins is transferred. In a full-term gestation IgG concentration is usually higher in the cord serum than in the mother serum. It has been shown that the ratio of cord/maternal IgG is higher when maternal IgG values are low. A series of 44 mother-child pairs from the north of Portugal were studied. Quantitative determination of IgG in all sera was made by single radial immunodiffusion and results were expressed in milligrams/deciliter (mg/dl). In the first 48 hours after delivery, mothers were interviewed and clinical, social and demographic data were collected. In 35 pairs, cord IgG exceeded the corresponding maternal concentration. The ratio of cord/maternal IgG ranged from 0.75 to 2.86 (mean 1.27). From all studied variables only maternal IgG concentration and age were correlated with that ratio. Transplacental concentration (ratio of cord/maternal IgG) was higher for lower levels of maternal IgG. Significant contribution of maternal age did not stand when a woman with extreme values of IgG and age was withdrawn from the analysis. Values found for this series of Portuguese mother-child pairs were similar to those found for other caucasian populations and are in agreement with current proposed models for placental transfer of IgG.