Background. The aim of this study was to prospectively evaluate plasma kisspeptin levels in 129 singleton pregnancies with diabetes [pregestational insulin-dependent diabetes mellitus (type 1) and gestational diabetes (GD)] and hypertensive disease [chronic hypertension (CH), gestational hypertension, and preeclampsia (PE)] as a potential marker of placental dysfunction and adverse perinatal outcome. Study design. Kisspeptin levels were evaluated in the first, second, and third trimesters in patients with type 1 diabetes (16 patients), H (22), and healthy control (25) and in the second and third trimesters in patients with GD (20), gestational hypertension (18), and PE (28). Maternal kisspeptin levels were correlated with pregnancy outcome, parameters of fetoplacental circulation, ultrasound-detected abnormalities of placental morphology, and placental weight at delivery. Results. In pregnancies with type 1 diabetes and H, mean kisspeptin levels were significantly lower compared with the control group (p < 0.001 in the first and second trimesters and p < 0.05 in the third trimester). Decreased plasma kisspeptin levels in the second and third trimesters were found in patients with GD (p < 0.001 in the second and third trimesters) and PE (p < 0.001 in the second trimester and p < 0.05 in the third trimester). In patients with PE and placental dysfunction, low kisspeptin levels in the third trimester were associated with adverse perinatal outcome. Conclusions. Our study demonstrates reduced kisspeptin levels in pregnancies with diabetes, H, PE, and placental dysfunction. In patients with PE and placental dysfunction, decreased kisspeptin levels were associated with adverse perinatal outcome. Larger studies are needed to investigate the role of kisspeptin as a potential marker of placental dysfunction and adverse perinatal outcome.