Predictive value of serum uric acid levels for adverse maternal and perinatal outcomes in pregnant women with high blood pressure. A systematic review and meta-analysis

Serum Uric Acid Levels as a Risk Stratification Tool in Hypertensive Disorders of Pregnancy: A Retrospective Study

BACKGROUND

Worldwide, hypertensive disorders of pregnancy (HDP) are among the leading causes of maternal and fetal morbidity and mortality. Serum uric acid is a test that can evaluate the severity of HDP and the associated maternal and fetal morbidity and mortality.

AIM

To examine the relationship between maternal serum uric acid levels and the severity of HDP and overall pregnancy outcomes.

MATERIAL AND METHODS

A retrospective study was conducted on women with a gestational age > 20 weeks and BP >140/90 mmHg over three years. A total of 134 patients were included in the study. Patients with chronic hypertension, hyperuricemia without hypertension, and other major illnesses were excluded. Data were collected from medical records, including age, gravida, parity, weight, height, gestational age, blood pressure at admission, urine albumin, and serum uric acid levels.

RESULTS

Of the 134 enrolled women with HDP, 76 had gestational hypertension, 41 had preeclampsia, and 17 had eclampsia. Mean uric acid levels in mg/dL were 6.06±1.651, 6.20±0.824, and 7.38±1.26 in gestational hypertension, preeclampsia, and eclampsia, respectively, which was a significant association (p=0.002). Mean uric acid in mg/dL was 5.86±1.27 in intensive care unit (ICU) patients compared to 6.45±1.39 in ward patients (p=0.015). There was a significantly increased risk of ICU admission and preterm delivery (r=-0.401, p<0.001) in patients with elevated uric acid levels. There was a significantly increased risk of low-birth-weight babies with elevated uric acid levels (r=-0.278, p=0.001). However, there was no statistically significant increased risk of newborn intensive care unit admissions (p=0.264) with elevated uric acid levels.

CONCLUSION

Serum uric acid levels vary significantly in HDP and were found to be elevated in severe preeclampsia and eclampsia. It can be considered for risk stratification in HDP based on disease severity; however, its role in determining outcomes is debatable. Using serum uric acid levels in predictive models along with known biomarkers may determine its possible additional value in disease prediction and severity.

Is salivary uric acid, a putative biomarker of pre-eclampsia, of maternal, placental, or fetal origin?

OBJECTIVES

Increased salivary uric acid (sUA) represents a potential biomarker predictive of pre-eclampsia (PE), but its origin is unclear. The study explores whether sUA levels reflect maternal or feto-placental physiological stress and whether sUA levels in these cases correlate with amniotic fluid (fetal origin), maternal blood (maternal origin), or cord blood (fetal vs placental origin).

STUDY DESIGN

Pregnant women (n = 39) undergoing amniotomy or caesarean section after 34 gestational weeks were designated into three groups of either maternal, feto-placental, or no signs of physiological stress: women (n = 15) in the established first phase of active labour and without any signs of fetal growth restriction (FGR) or PE were assigned to the maternal stress group, women (n = 6) with an ultrasound-based diagnosis of FGR, with or without PE, were assigned to the feto-placental stress group, and women (n = 18) not yet in active labour and without any signs of FGR or PE, were assigned to the control group. Uric acid levels in corresponding samples of amniotic fluid, saliva, maternal blood, and cord blood were compared between groups and between body compartments within each group.

RESULTS

The feto-placental stress group showed increased UA levels in saliva (median, interquartile range [IQR]: 0.47 [0.38] mmol/L, P = 0.023) and maternal blood (0.42 [0.13] mmol/L, P = 0.032), but no differences in amniotic fluid or cord blood compared with the other groups. Within the control and maternal stress group, sUA levels were lower compared with maternal blood (0.20 [0.08] vs 0.25 [0.08] mmol/L, Pcontrol = 0.018; 0.20 [0.06] vs 0.26 [0.08] mmol/L, Pmaternal = 0.001) and highest in amniotic fluid (control group (0.49 [0.18] mmol/L): Pmaternal,blood = 0.001, Pumbilical,artery = <0.001, Pumbilical,vein = <0.001, Psaliva = <0.001) (maternal stress group (0.56 [0.23] mmol/L): Pmaternal,blood = 0.021, Pumbilical,artery = 0.006, Pumbilical,vein = 0.004, Psaliva = 0.003). Levels did not differ between compartments in the feto-placental stress group.

CONCLUSIONS

Salivary and maternal blood UA levels were increased in the feto-placental stress group with salivary levels increasing more than blood levels compared with the maternal stress and control groups, whilst UA in amniotic fluid were not different between the groups, suggesting a placental origin and potential use of sUA as a biomarker of placental dysfunction, including FGR and severe PE.

The association of maternal serum uric acid with the risk of small for gestational age newborn: a retrospective cohort study

PROBLEM

Prior results on the association between serum uric acid (UA) levels in the early trimester and the risk of small for gestational age (SGA) remain unclear. This study evaluated the association of maternal first-, second-, and third-trimester UA levels with the risk of SGA infants.

METHOD OF STUDY

A total of 23, 194 singleton mothers from the International Peace Maternity and Child Health Hospital between January 2014 and January 2017 were included. Maternal UA levels were measured at 12.1 ± 1.08th (UA1) and 32.2 ± 1.03th (UA2) gestational weeks. △UA was calculated as the difference between UA2 and UA1. Logistic regression and restricted cubic spline (RCS) were performed to evaluate the association between maternal UA and △UA during pregnancy and SGA. Receiver operating characteristic (ROC) analysis was employed to assess the serum uric acid prediction value.

RESULTS

Women in the higher quartiles of UA1 had a significantly higher risk of SGA. A clear increased risk for SGA was observed with higher quartiles for UA2 (p for trend <0.05). An approximately "J-shaped" relationship was observed between UA2 and △UA, and the risk of SGA was observed. When compared with those with a lower level of UA in the first trimester, those with a higher level of UA1, the more increase in the later UA levels were associated with a higher risk of SGA [adjusted odds ratio (aOR) = 1.67, 95% CI:1.37-2.05]. The ROC curve areas were 0.525 for UA1, 0.582 for UA2 and 0.576 for △UA.

CONCLUSIONS

The findings suggested that non-preeclamptic and non-hypertensive women who experienced early pregnancy with high UA levels had an elevated risk of SGA. Moreover, a high maternal UA level in the earlier trimester may be an early predictor of SGA.

Impact of Angiogenic and Cardiovascular Biomarkers for Prediction of Placental Dysfunction in the First Trimester of Pregnancy

Algorithms for first-trimester prediction of pre-eclampsia usually include maternal risk factors, blood pressure, placental growth factor (PlGF), and uterine artery Doppler pulsatility index. However, these models lack sensitivity for the prediction of late-onset pre-eclampsia and other placental complications of pregnancy, such as small for gestational age infants or preterm birth. The aim of this study was to assess the screening performance of PlGF, soluble fms-like tyrosine kinase-1 (sFlt-1), N-terminal pro-brain natriuretic peptide (NT-proBNP), uric acid, and high-sensitivity cardiac troponin T (hs-TnT) in the prediction of adverse obstetric outcomes related to placental insufficiency. This retrospective case-control study was based on a cohort of 1390 pregnant women, among which 210 presented pre-eclampsia, small for gestational age infants, or preterm birth. Two hundred and eight women with healthy pregnancies were selected as controls. Serum samples were collected between weeks 9 and 13 of gestation, and maternal serum concentrations of PlGF, sFlt-1, NT-proBNP, uric acid, and hs-TnT were measured. Multivariate regression analysis was used to generate predictive models combining maternal factors with the above-mentioned biomarkers. Women with placental dysfunction had lower median concentrations of PlGF (25.77 vs. 32.00 pg/mL; p < 0.001), sFlt-1 (1212.0 vs. 1363.5 pg/mL; p = 0.001), and NT-proBNP (51.22 vs. 68.71 ng/L; p < 0.001) and higher levels of uric acid (193.66 µmol/L vs. 177.40 µmol/L; p = 0.001). There was no significant difference between groups regarding the sFlt-1/PlGF ratio. Hs-TnT was not detected in 70% of the maternal serums analyzed. Altered biomarker concentrations increased the risk of the analyzed complications both in univariate and multivariate analyses. The addition of PlGF, sFlt-1, and NT-proBNP to maternal variables improved the prediction of pre-eclampsia, small for gestational age infants, and preterm birth (area under the curve: 0.710, 0.697, 0.727, and 0.697 vs. 0.668, respectively). Reclassification improvement was greater in maternal factors plus the PlGF model and maternal factors plus the NT-p roBNP model (net reclassification index, NRI: 42.2% and 53.5%, respectively). PlGF, sFlt-1, NT-proBNP, and uric acid measurements in the first trimester of pregnancy, combined with maternal factors, can improve the prediction of adverse perinatal outcomes related to placental dysfunction. In addition to PlGF, uric acid and NT-proBNP are two promising predictive biomarkers for placental dysfunction in the first trimester of pregnancy.

Hyperuricemia during Pregnancy Leads to a Preeclampsia-Like Phenotype in Mice

Hyperuricemia is a common feature in pregnancies compromised by pre-eclampsia, a pregnancy disease characterized by hypertension and proteinuria. The role of uric acid in the pathogenesis of pre-eclampsia remains largely unclear. The aim of this study was to investigate the effect of elevated uric acid serum levels during pregnancy on maternal blood pressure and neonatal outcome using two different murine knockout models. Non-pregnant liver-specific GLUT9 knockout (LG9KO) mice showed elevated uric acid serum concentrations but no hypertensive blood pressure levels. During pregnancy, however, blood pressure levels of these animals increased in the second and third trimester, and circadian blood pressure dipping was severely altered when compared to non-pregnant LG9KO mice. The impact of hyperuricemia on fetal development was investigated using a systemic GLUT9 knockout (G9KO) mouse model. Fetal hyperuricemia caused distinctive renal tissue injuries and, subsequently an impaired neonatal growth pattern. These findings provide strong evidence that hyperuricemia plays a major role in the pathogenesis of hypertensive pregnancy disorders such as pre-eclampsia. These novel insights may enable the development of preventive and therapeutic strategies for hyperuricemia-related diseases.

Relationship between maternal serum uric acid level and preeclampsia with or without severe features

Hyperuricaemia is common in preeclampsia. Its relationship and the utility in predicting of preeclampsia must be evaluated. The objective was to determine the association between maternal serum uric acid level and preeclampsia with or without severe features, including maternal and neonatal outcomes. A retrospective study was conducted at Rajavithi Hospital between June 2015 and May 2019. Inferential analysis comparison using binary logistic regression analysis and correlation using Chi-Square test/Fisher's exact test were used for analysis. Among the 400 participants, 331 (82.7%) women were preeclampsia with severe features. The mean uric acid level was significantly higher in women with preeclampsia with severe features compared to those without (6.44 ± 1.44 vs 5.87 ± 1.53 mg/dL, p-value = .016). Uric acid greater than 7 mg/dL was associated with renal involvement and preeclampsia with severe features. Uric acid 5-7 and greater than 7 mg/dL correlated with preterm birth (OR 2.67, 95% CI 1.59-4.49 and OR 4.89, 95% CI 2.75-8.68, respectively). Uric acid greater than 7 mg/dL also increased the risk of RDS and NICU admission. In conclusion, a high uric acid level is associated with preeclampsia with severe features and adverse pregnancy outcomes and may be the predictor of the severity of preeclampsia.Impact statementWhat is already known on this subject? Hyperuricaemia is a common finding in preeclamptic pregnancy due to reduction of uric acid clearance secondary to reduced glomerular filtration rate, increased reabsorption, and decreased secretion. The correlation of increase maternal uric acid level and preeclampsia including adverse pregnancy outcomes has been evaluated and supported the use of uric acid as a predictor for preeclampsia development. However, its clinical utility is still debateable.What the results of this study add? The present study demonstrated the association between higher maternal serum uric acid level and severity of preeclampsia. Particularly, serum uric acid greater than 7 mg/dL was associated with preeclampsia with severe features. Additionally, serum uric acid level 5-7 mg/dL and greater than 7 mg/dL had a positive correlation with adverse maternal and neonatal outcomes.What the implications are of these findings for clinical practice and/or further research? Maternal serum uric acid may be used as the predictor of severity of preeclampsia. However, the sensitivity and specificity and the precise clinical utility of uric acid related to preeclampsia need to be further evaluated in larger sample size.

Hypertensive Disorders of Pregnancy: Common Clinical Conundrums

Importance

Hypertensive complications of pregnancy comprise 16% of maternal deaths in developed countries and 7.4% of deaths in the United States. Rates of preeclampsia increased 25% from 1987 to 2004, and rates of severe preeclampsia have increased 6.7-fold between 1980 and 2003.

Objective

The aim of this study was to review current and available evidence for common clinical questions regarding the management of hypertensive disorders of pregnancy.

Evidence Acquisition

Original research articles, review articles, and guidelines on hypertension in pregnancy were reviewed.

Results

Severe gestational hypertension should be managed as preeclampsia with severe features. Serum uric acid levels can be useful in predicting development of superimposed preeclampsia for women with chronic hypertension. When presenting with preeclampsia with severe features before 34 weeks, expectant management should be considered only when both maternal and fetal conditions are stable. In the setting of hypertensive disorders of pregnancy, oral antihypertensive medications should be initiated when systolic blood pressure is greater than 160 mm Hg or when diastolic blood pressure is greater than 110 mm Hg, with the most ideal agents being labetalol or nifedipine. Furthermore, although risk of preeclampsia recurrence in future pregnancy is low, women with a history of preeclampsia should be managed with 81 mg aspirin daily for preeclampsia prevention.

Conclusions and Relevance

Despite the frequency with which hypertensive disorders of pregnancy are encountered clinically, situations arise frequently with limited evidence to guide providers in their management. An urgent need exists to better understand this disease to optimize outcomes for impacted patients.

Assessing the Role of Uric Acid as a Predictor of Preeclampsia

We assessed the diagnostic utility of uric acid for the prediction of preeclampsia. An observational prospective approach was carried out during 2014. Preeclamptic women were classified into 4 groups accordingly to the onset of preeclampsia and the presence of intrauterine growth restriction (IUGR). Serum uric acid levels, urea, and creatinine were measured. Receiver operating curves (ROC) of the uric acid levels ratio (UAr) between a dosage before and after the 20th week of gestation were performed. One thousand two hundred and ninety-third pregnant women were enrolled in this study. Eight hundred ten had non-complicated pregnancies, 40 preeclampsia, 33 gestational hypertension, and 20 IUGR without preeclampsia. Uric acid significantly raised after 20 weeks of gestation in women who develop preeclampsia before 34 weeks (Group A) or in those who develop preeclampsia after 37 weeks associated with IUGR (Group C). In women who develop preeclampsia after 34 weeks without IUGR (Groups B and D), uric acid increased after the 30th week of gestation. In all groups, UAr was greater than 1.5. In gestational hypertension, UAr was superior to 1.5 toward the end of gestation, while in IUGR without preeclampsia, the behavior of serum uric acid was similar to non-complicated pregnancies. In all cases, urea and creatinine showed normal values, confirming that patients had no renal compromise. ROC area was 0.918 [95% confidence interval (CI): 0.858–0.979) for the preeclampsia group and 0.955 (95% CI: 0.908–1.000) for Group A. UAr at a cut-off point ≥1.5 had a very low positive predictive value, but a high negative predictive value of 99.5% for preeclampsia and it reached 100% for Group A. Thus, a UAr less than 1.5 may be a helpful parameter with a strong exclusion value and high sensitivity for those women who are not expected to develop preeclampsia. Additionally, this low-cost test would allow for better use of resources in developing countries.

Characterizing and Evaluating Diurnal Salivary Uric Acid Across Pregnancy Among Healthy Women

Uric acid levels during pregnancy have been examined as a potential indicator of risk for gestational diabetes mellites, hypertension, and related adverse birth outcomes. However, evidence supporting the utility of serum uric acid levels in predicting poor maternal and fetal health has been mixed. The lack of consistent findings may be due to limitations inherent in serum-based biomeasure evaluations, such as minimal repeated assessments and variability in the timing of these assessments. To address these gaps, we examined repeated measurements of diurnal salivary uric acid (sUA) levels in a sample of 44 healthy women across early-mid and late pregnancy. We assessed potential covariates and confounds of sUA levels and diurnal trajectories, as well as associations between maternal weight gain and blood pressure during pregnancy and sUA concentrations. Using multilevel linear models, we found sUA increased across pregnancy and displayed a robust diurnal pattern with the highest concentrations at waking, a steep decline in the early morning, and decreasing levels across the day. Maternal pre-pregnancy BMI, age, prior-night sleep duration, and fetal sex were associated with sUA levels and/or diurnal slopes. Maternal blood pressure and gestational weight gain also showed significant associations with sUA levels across pregnancy. Our results expand upon those found with serum UA measurements. Further, they demonstrate the feasibility of using at-home, minimally-invasive saliva sampling procedures to track UA levels across pregnancy with potential applications for the long-term monitoring of maternal cardiometabolic risk.

Moringa oleifera polysaccharides regulates caecal microbiota and small intestinal metabolic profile in C57BL/6 mice

This study investigated the effects of Moringa oleifera polysaccharides (MOP) on the serum indexes, small intestinal morphology, small intestinal metabolic profile, and caecal microbiota of mice. A new type of polysaccharides with 104,031 Da molecular weight and triple helix structure was isolated from M. oleifera leaves for in vivo experiment. Forty male SPF C57BL/6 mice aged 4 weeks were average divided into four groups randomly according to the MOP gavaged daily (0, 20, 40 and 60 mg/kg body weight MOP). After a 7-day preliminary trial period and a 28-day official trial period, the mice were slaughtered. Results showed that MOP reduced glucose, total cholesterol, and malondialdehyde. It also improved superoxide dismutase and catalase in serum (P < 0.05). For small intestinal morphology, MOP improved the villi length and crypt depth in both ileum and jejunum (P < 0.05); the ratio of villi length to crypt depth in jejunum increased (P < 0.05). MOP could cause the increase of beneficial bacteria and the decrease of harmful bacteria in caecum, further affecting the function of microbiota. In addition, MOP regulated 114 metabolites enriched in the pathway related to the synthesis and metabolism of micromolecules. In sum, MOP exerted positive effects on the serum indexes and intestinal health of mice.