Impaired glucose tolerance during pregnancy is associated with increased fetal mortality in preceding sibs

To analyze whether women with a diagnosis of gestational diabetes in the current pregnancy had an increased rate of stillbirths or of large for gestational age infants in previous pregnancies without an overtly present/diagnosed gestational diabetes.

A case-control analysis with two controls for each case, matched for year of delivery, maternal age (5 year class), and parity.

All women with a diagnosis of gestational diabetes and delivered between 1987 and 1992 were identified from the Swedish Medical Birth Registry. For each woman, the first delivery with that diagnosis was used as proband case (n = 3,958). To each case and control, all previous sibs since 1973 were identified. Comparisons were made between cases and controls but also between sibs of cases and sibs of controls.

No significant difference was found in stillbirth rate between cases and controls (OR 1.33, CL 0.64;2.77). The rate of intrauterine deaths was significantly increased among previous sibs of the cases compared with the sibs of the controls: after stratification for year of birth, maternal age and parity an odds ratio of 1.56 (95% CL 1.12;2.19) was found. Infants born of women with gestational diabetes were heavier (mean 145 g, 95% CL 123;168 g). Similar differences were seen between immediately previous sibs of cases and controls (mean 155 g, 95% CL 127;183 g).

The figures indicate that in pregnancies before a delivery with gestational diabetes the perinatal prognosis was significantly poorer than expected which could be due to the presence of undiagnosed and untreated gestational diabetes. The results argue for an improved screening for gestational diabetes during pregnancy.