Total IgG and tetanus antibodies were evaluated in 2 series of mother-child pairs: 50 in Paris and 134 in Africa. All pregnancies had been normal and birth weights greater than 3 kg. Cord blood mothers tetanus antibodies ratios were 1.5 in Paris and 0.98 in Libreville (p less than 0.01) respectively. Some African children were not protected, either due to the lack of response of their mothers to immunization (2.2%) or to an insufficient antibodies transplacental transport (2.9%), or to the lack of immunization of mothers (5.9%). On the contrary, all European children were protected, in spite of low maternal antibody levels. Likewise, in Paris cord blood IgG level was 12.24 g/l vs 9.42 in mothers (cord blood/mother ratio: 1.34) and in Africa 18.4 g/l in cord blood and 22.3 g/l in mothers (cord blood/mother ratio: 0.88; p less than 0.01). The correlations between maternal IgG levels and placental transfer rates indicate that the transplacental active transfer is limited by common high IgG levels in Africa, thus contributing to a decrease in protection of neonates, especially against tetanus in which humoral responses predominate.