The average insulin level in the amniotic fluid rises between the 27th and 40th week of pregnancy from 8 muU/ml to 17 muU/ml (n equal to 62). In diabetic pregnancy, the insulin level in the amniotic fluid is in the average elevated to 488%. This indicates oversupply of glucose to the fetus. In the healthy fetus the intercellular apparatus reacts by overproduction of insulin. Part of this insulin reaches the amniotic fluid via the urine. The fetus is in the paradoxical situation of showing simultaneously elevated glucose and insulin levels. The resulting surfeit of insulin is the cause of diabetogenic fetal morbidity. Amniotic fluid insulin levels can be used both to evaluate diabetogenic fetal morbidity, and in order to allow metabolic compensation with insulin to be carried out in accordance with fetal parameters in pregnancy. Examination of the amniotic fluid at bi-weekly intervals from week 27 on thus provides a means of adjusting the metabolic compensation with insulin in the diabetic mother in such a way that diabetogenic fetal morbidity is prevented.