Blood glucose and insulin relationships in the human mother and fetus before onset of labour.

The effects of a maternal intravenous glucose load on the fetal plasma levels of glucose and insulin have been studied in 11 patients before the onset of labour. Within five minutes the fetal plasma glucose concentration rose significantly, indicating a rapid transfer of glucose across the placenta. Following this, the rate of fall in fetal plasma glucose closely reflected that in the mother.Serial fetal insulin estimations carried out in 8 of the 11 subjects following maternal glucose showed an early rise in fetal insulin in four and a delayed rise in one; in the remaining three there was no definite change.It is concluded that the blood glucose level of the fetus is controlled by that of the mother, but that the fetal pancreas at term may respond to hyperglycaemia by the secretion of insulin.