The study of 230 diabetic mothers along with their newborn babies has shown that foetal macrosomia is associated with two specific genomic sites: phosphoglucomutase locus 1 (PGM1)-Rhesus blood group (Rh) linkage group (chromosome 1) and HindIII restriction fragment length polymorphism (RFLP) linked to insulin-like growth factor 1 (IGF1) (chromosome 12). In PGM(1)2-1 mothers carrying the E allele, there is a proportion of 8.7% of macrosomic newborns as compared with 39.6% in mothers with other genotypes. The relationship between the maternal PGM1-RhE genotype and neonatal macrosomia does not depend on the type of diabetes. The proportion of macrosomic infants is much lower among newborns carrying the IGF1HS allele of the HindIII RFLP linked to IGF1 (20%) than among IGF1F/IGF1HF newborns (55%).