Aim: To evaluate whether initiation of anti-hypertensive treatment with methyldopa affects fetal hemodynamics in women with pregestational diabetes. Methods: Prospective study of unselected singleton pregnant women with diabetes (seven type 1 and two type 2 diabetes), normal blood pressure and kidney function at pregnancy booking. Methyldopa treatment was initiated at blood pressure >135/85 mmHg and/or urinary albumin excretion (UAE) >300 mg/g creatinine. Pulsatility indices (PI) of the uterine, umbilical, middle cerebral arteries before and 1 week after initiation of methyldopa treatment (250 mg three times daily) was performed and the cerebro-placental ratio (CPR) was calculated. Results: Methyldopa treatment was initiated at median 249 (range 192–260) gestational days, mainly due to gestational hypertension (n = 7). Blood pressure declined from 142 (112–156)/92 (76–103) mmHg before to 129 (108–144)/82 (75–90) mmHg after initiation of methyldopa treatment (p = 0.11 and 0.04 for systolic and diastolic blood pressure, respectively). There were no significant changes in the umbilical artery PI (0.82 (0.72–1.40) versus 0.87 (0.64–0.95),p = 0.62) or CPR (1.94 (0.96–2.33) versus 1.78 (1.44–2.76), (p = 0.73). Gestational age was 265 (240–270) d. Apgar scores were normal. Conclusions: Stable Doppler flow velocity waveforms were documented after initiation of methyldopa treatment for pregnancy-induced hypertensive disorders in this cohort of pregnant women with pregestational diabetes. [ABSTRACT FROM PUBLISHER]