Studies suggest that maternal diabetes can cause both placental insufficiency and exaggerated foetal growth. Pregnant mothers with diabetes have suffered high risk of losing their child. Data from the Medical Birth Registry of Norway show a decrease in the still birth rate from 16th week of gestation from 115.7 per 1,000 in 1967-75 to 12.8 in 1986-92 in the diabetes groups. The relative risks were 7.8 and 1.4 respectively for the two time periods. The early neonatal mortality rate decreased correspondingly. The proportion of Caesarean sections in mothers with diabetes, and the proportion of children with low birth weight or born prematurely also increased in the diabetes group. However, children in the diabetes group were on average still as big at gestational age in the most recent period as in the first period. Our data suggest that the improved metabolic control of maternal diabetes has reduced the occurrence and degree of placental insufficiency, with inherent decreases in mortality and risk of complications, but without reducing the foetal growth-stimulating effect of maternal diabetes.