ABSTRACT Objective There is growing evidence that pregnant women with gestational hypertension are more likely to develop cardiovascular disease in the future, including arrhythmias. The objective of this study was to analyze changes in electrocardiogram (ECG) parameters in pregnant women with gestational hypertension and identify independent risk factors for preeclampsia. Materials and Methods We collected the ECG data of 185 pregnant women and classified them into three groups: the first group was 68 healthy pregnant women in the third trimester, the second group was 61 pregnant women with gestational hypertension (without preeclampsia), and the third group was 56 pregnant women with preeclampsia. P‐wave amplitude, P‐wave dispersion (PWD), P‐wave area (PWA), ventricular activation time (VAT), T‐wave peak‐to‐end interval (Tp‐e interval), maximum QTc interval (QTc max), and QTc dispersion (QTc‐d) were measured. Results Ordered logistic regression revealed significant differences in PWD, QTc max, Tp‐e interval, and QTc‐d values among the three groups. However, only PWD and QTc‐d values were significantly higher in the preeclampsia group than in the non‐preeclampsia group by binary logistic regression. Using a cut‐off of ≥ 35.5 ms for the PWD achieved an accuracy of 74.8% in diagnosing preeclampsia (sensitivity 92.86%, specificity 56.59%). Using a cut‐off of ≥ 43.5 ms for the QTc‐d achieved an accuracy of 91.8% (sensitivity 85.71%, specificity 84.50%). Conclusions PWD and QTc‐d were identified as independent ECG risk factors for preeclampsia. Monitoring these parameters may help screen high‐risk pregnant women and improve the management of those with a history of gestational hypertension or preeclampsia.