Relationship between serum uric acid, nocturnal hypertension and risk for preeclampsia in high-risk pregnancies.

To analyze the possible association between serum uric acid (SUA) and nocturnal hypertension and to evaluate the ability of these variables (alone or in combination) to predict preeclampsia (PE) we conducted a historical cohort study in 532 high-risk pregnancies. Women were divided according to SUA values and nocturnal blood pressure (BP) into four groups: 1- normal SUA and nocturnal normotension; 2- high SUA and nocturnal normotension; 3- normal SUA and nocturnal hypertension and 4- high SUA and nocturnal hypertension. High SUA was defined by the top quartile values and nocturnal hypertension as BP ≥ 120/70 mmHg, using ambulatory blood pressure monitoring (ABPM), during nocturnal rest. Risks for PE were compared using logistic regression. SUA had a weak but significant correlation with daytime systolic ABPM (r = 0.11, p = 0.014), daytime diastolic ABPM (r = 0.13, p = 0.004), nighttime systolic ABPM (r = 0.16, p < 0.001) and nighttime diastolic ABPM (r = 0.18, p < 0.001). Also, all ABPM values were higher in women with high SUA. The absolute risk of PE increased through groups: 6.5%, 13.1%, 31.2%, and 47.9% for groups 1, 2, 3, and 4, respectively, p < 0.001. Compared with Group 1, Group 3 (OR 6.29 95%CI 3.41-11.60), but not Group 2 (OR 2.15 95%CI 0.88-5.24), had statistically significant higher risk for PE. Group 4 (women with both, high SUA and nocturnal hypertension) had the highest risk (OR 13.11 95%CI 6.69-25.70). Risks remained statistically significant after the adjustment for relevant variables. In conclusion, the combination of SUA > 4 mg/dL and nocturnal BP > 120/70 mmHg implies a very high risk to developed PE.