Findings show that women with gestational diabetes are at risk of frequent episodes of asymptomatic hypoglycaemia. Eighty-two women with gestational diabetes were studied using continuous glucose monitoring for 72 hours (the system provided more than 750 blood glucose measurements during this period). 30 of these women were treated with insulin, 25 with gliburide and 27 remained on diet only. As many as 63% of the insulin-treated and 28% of the gliburide-treated women experienced asymptomatic periods lasting more than 30 minutes in which blood glucose levels fell below 50 mg %. Insulin-treated patients had an average of 4.2 such periods per day, most of them at bedtime. Patients treated with gliburide had an average of 2.1 such episodes with the same frequency during the day and night. Thus, it seems that the occurrence of such episodes is related to the method of treatment rather than to the disease itself. The question remains as to what are the clinical implications of such brief hypoglycaemic episodes for both maternal and foetal well-being in a diabetic pregnancy.