Is there a genetic basis for gestational diabetes?

Rh E-PGM1 (phosphoglucomutase locus 1) joint genotype frequencies (chromosome 1) have been determined in 90 women with gestational diabetes mellitus (GDM) and in 140 pregnant women with preexisting insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). The pattern of Rh E-PGM1 association differs among types of diabetes. The distortion of the pattern tends to assume opposite values in GDM and NIDDM and this is particularly evident in PGM12,2 subjects. The proportion of PGM12,2 subjects homozygous for the Rh e allele is higher in GDM than in IDDM and NIDDM. IDDM women show an intermediate proportion and NIDDM women show the lowest proportion of this genotype. The opposite pattern is observed among PGM1*2,2 subjects carrying the Rh E allele. Genotype frequencies of the hypervariable region flanking the insulin gene (chromosome 11) have been determined in 77 women with GDM, in 52 pregnant women with preexisting diabetes (IDDM and NIDDM), and in 62 normal adults. In GDM and NIDDM subjects the frequencies are similar. In IDDM women the frequency of homozygotes for the class 1 allele is higher than the frequency found in GDM and NIDDM women. The data suggest a possible genetic basis for the differentiation of a subclass of GDM from both IDDM and NIDDM.