Blood levels of the monosialoganglioside GM1 (nomenclature according to Svennerholm) were tested at birth in the umbilical cord of 37 neonates and their mothers. Comparisons were made based on gestational age and modality of delivery. GM1 blood levels at birth were significantly higher in mothers than in newborns (373.66 +/- 56.83 ng/ml vs 217.95 +/- 21.24 ng/ml; P < 0.01). Newborns delivered by cesarean section showed levels of GM1 significantly higher than those delivered vaginally (298.97 +/- 38.55 ng/ml vs 169.62 +/- 12.62 ng/ml; P < 0.01), and preterm newborns had significantly higher levels of GM1 than full-term newborns (253.50 +/- 40.83 ng/ml vs 193.71 +/- 21.74 ng/ml; P < 0.01). No differences in blood levels of GM1 were observed in the mothers in relation to length of pregnancy or modality of delivery. The higher levels of GM1 observed in preterm newborns indicate an increased turnover and/or enhanced bioavailability of the monosialoganglioside GM1 for the developing central nervous system. Further data are required to evaluate the significance of the increased cord levels of GM1 in neonates after cesarean section.