Abstract:Objective To investigate the clinical value of 24-hour ambulatory blood pressure monitoring (ABPM) during mid pregnancy for early warning of preeclampsia (PE) and adverse pregnancy outcomes. Method A total of 81 singleton pregnant women who were first found to have critical blood pressure during mid-term prenatal checkups were randomly selected, and 24-hour ABPM was performed to track their pregnancy outcomes. According to whether concurrent PE occurred, the subjects were divided into a normal group (49 cases) and a PE group (32 cases) to compare the general condition of the pregnant women and 24-hour ABPM parameters between the two groups, and logistic regression was used to analyze early warning factors for the occurrence of PE; at the same time, based on blood pressure patterns, the subjects were divided into three groups: dipper group (28 cases), non-dipper group (32 cases), and reverse-dipper group (21 cases), to analyze the correlation between circadian blood pressure fluctuations and maternal and fetal outcomes. Result When the PE group was first found to have borderline blood pressure, both diastolic pressure and the prevalence of random urine protein positivity were higher than those in the normal group (P< 0.01), and the gestational week at the first discovery of critical blood pressure was significantly earlier than in the normal group (P=0.001). The PE group had significantly higher 24-hour, daytime, and nighttime average systolic and diastolic blood pressure compared to the normal group (P<0.01). The incidence of PE in reverse-dipper group, non- dipper group, and dipper blood pressure group was 53.1%, 12.5%, and 34.4%, respectively, with statistically significant differences among three groups (χ²=22.899, P<0.01), and the incidence of PE in reverse-dipper blood pressure group was higher than that in non-dipper group and dipper group (P<0.017). Multivariate logistic regression analysis showed that early gestational week at first detection of borderline blood pressure, high diastolic blood pressure on the outpatient day, high morning peak blood pressure, and non-dipper/reverse-dipper blood pressure were independent warning factors for PE (P<0.05). There were statistically significant differences among the three groups in gestational week at delivery, cesarean section rate, and incidence of fetal growth restriction (FGR) (P<0.05) ; the reverse-dipper group had lower gestational week at delivery (P<0.017) but higher cesarean section and FGR rates compared to the dipper group (P<0.017) ; trend χ² test indicated that as the nocturnal decline in blood pressure decreased (dipper → non-dipper→ reverse-dipper), the rates of preterm birth showed a significant increasing trend (linear χ²=5.245, P=0.022). Conclusion Among pregnant women with borderline blood pressure in mid-pregnancy, the ABPM parameters are significantly elevated with disrupted blood pressure circadian rhythm. The gestational week at the first detection of borderline blood pressure, diastolic blood pressure on the outpatient day, morning peak blood pressure, and blood pressure pattern are important early warning factors for PE. Moreover, abnormal blood pressure circadian rhythm is closely associated with adverse maternal and fetal outcomes such as cesarean section rate and FGR. 24-hour ABPM in mid-pregnancy can provide early warning of PE and indicate adverse pregnancy outcomes.