Objective: We investigated whether blood pressure profile early in pregnancy was associated with the development of pre-eclampsia in patientswith gestational diabetesmellitus(GDM).Methods: A retrospective longitudinal database study of 1664 GDM subjects was performed. Systolic and diastolic blood pressure measurements were taken bi-weekly during the first and second trimesters. GDM patients who developed pre-eclampsia were compared to GDM patients who did not. Subjects were further stratified by maternal age, parity, race, prepregnancy body mass index (BMI) and weight gain during pregnancy. Logistic regression was performed to identify the net effect of each factor on the development of pre-eclampsia.Results: Overall, 167/1664 (10%) GDM patientsdeveloped pre-eclampsia.GDM patients who developed pre-eclampsia were more obese, gained more weight during pregnancy and had more severe GDM in comparison to GDM patients who did not. Although all mean blood pressure measurements were within the normal range, significantly higher systolic and diastolic valueswere recorded in the GDM patientswho developed pre-eclampsia throughout the first and the second trimesters of pregnancy. Logistic regression revealed that higher parity (p=0.04), maternal age (p=0.03) and pre-pregnancy BMI (p=0.03) were all contributing factors to pre-eclampsia. In contrast, weight gain during pregnancy and race were not related.Conclusion: In GDM patients, higher blood pressure readings early in pregnancy, even prior to GDM diagnosis, were associated with the subsequent development of pre-eclampsia.