56 out of the 200 pregnant diabetic women admitted to our clinic between July 1981 and June 1983 had followed a pre-pregnancy metabolic intensive treatment programme. Most of these patients achieved near-normoglycemia: 87% or more of all their blood glucose readings before conception and in the early weeks of gestation were normoglycemic. The 56 patients were delivered of 57 babies, one of them suffering from fatal heart malformation. The 144 pregnant diabetics who were admitted to hospital only after eight weeks of pregnancy and had not had any special preconceptional metabolic control gave birth to 145 children, 9 of which presented congenital malformations: 3 of these were fatal another 3 were severe, and 3 were minor. These data are in line with our previously reported results on the years 1977-81. They stress the importance of a reasonably strict metabolic control, started well before conception, to prevent excess rates of congenital malformation.