Impact of Diurnal Variation on Umbilical Artery Doppler Measurements in Pregnancies Complicated by Hypertensive Disorders

Objective: The study aims to determine whether the time of day influences these parameters compared to normotensive pregnancies. Materials and Methods: This prospective, single-center study included 60 pregnant women diagnosed with hypertensive disorders (gestational hypertension, chronic hypertension, or preeclampsia) and 60 normotensive controls, all between 30 and 37 weeks of gestation. Umbilical artery Doppler measurements were performed twice daily, between 08:00-10:00 and 20:00-22:00, by the same experienced operator. Measurements were taken at both the fetal and placental ends of the umbilical artery, recording systolic/diastolic ratios, pulsatility index, and resistance index values. Results: In Doppler measurements, the morning and evening evaluations revealed that S/D, PI, and RI values near the fetus and placenta were significantly higher in the study group compared to the control group. Notably, in the preeclampsia subgroup, the morning S/D values (3.3±1.1 vs. 2.3±0.5, p