The role of maternal serum fructosamine estimation in the management of gestational diabetes was assessed in 78 consecutive patients over a 3-year period. Fructosamine results correlated significantly with mean plasma glucose levels over a 1- to 3-week interval, with the closest association being in the preceding week. Eighty-five percent of women with gestational diabetes had peak serum fructosamine levels above the normal range. If maternal levels exceeded 3.2 mmol/L, there was an 88% chance of abnormal glucose tolerance post partum. Our aim of management was a serum fructosamine level less than 2.5 mmol/L; patients who achieved this goal by 35 to 37 weeks' gestation had fewer obese babies with lower cord insulin and C-peptide levels as compared with neonates of mothers with elevated fructosamine concentrations.