Recurrent hypoglycaemia associated with first and second trimester insulin sensitivity in a patient with insulin-dependent diabetes.

A 35-year-old insulin-dependent diabetic woman presented at 8 weeks gestation with multiple severe hypoglycaemic episodes occurring during the day and night without warning. Her pre-pregnancy insulin dosage of 45 units daily was progressively reduced by 73% to 12 units daily by week 17 because of multiple hypoglycaemic episodes. Investigation showed no pathological cause for the hypoglycaemia. Insulin dosage increased to 16 units daily by week 19 and then increased sharply to 60 units daily at 23 weeks and finally to 72 units at week 37. Following delivery her insulin dosage returned to pre-pregnancy values. Insulin-dependent diabetic women may rarely develop exaggerated insulin sensitivity in the first trimester of pregnancy resulting in severe hypoglycaemia, but spontaneous improvement occurs with increasing insulin resistance in the second and third trimesters.