Salivary uric acid as a predictive test of preeclampsia, pregnancy‐induced hypertension and preterm delivery: A pilot study

Abstract

Introduction There remains a need for a non‐invasive, low‐cost and easily accessible way of identifying women at risk of developing hypertensive disorders in pregnancy. This study evaluated the predictive value of longitudinal salivary uric acid measurement. Material and methods Pregnant women (n = 137) from 20 weeks of gestation were recruited at St Richards Hospital, Chichester, UK, for this prospective cohort study. Weekly samples of salivary uric acid were analyzed until delivery. Information regarding pregnancy and labor were obtained from the patient’s record after delivery. Independent t tests were used to compare mean levels of salivary uric acid in women with hypertensive complications and adverse fetal outcomes with women with normal pregnancies. Main outcome measures were preeclampsia, pregnancy‐induced hypertension, spontaneous preterm delivery and small‐for‐gestational‐age babies. Results From 21 weeks of gestation until delivery, levels of salivary uric acid increased significantly in women who subsequently developed preeclampsia and pregnancy‐induced hypertension compared with women with normal pregnancies (preeclampsia—mean at gestational age 21‐24, 95% confidence interval [95% CI] [mean GA21‐24): 108 [63‐185] vs 47 (39‐55) µmol/L; P = .005; pregnancy‐induced hypertension—mean GA21‐24: 118 [54–258] vs 47 [39‐55] µmol/L; P = .004). In women who had spontaneous preterm delivery, salivary uric acid levels increased significantly from 29 to 32 weeks of gestation compared with women with normal pregnancies (mean GA29‐32: 112 (57‐221) vs 59 (50‐71) µmol/L; P = .04). In women who had babies small‐for‐gestational‐age <10th percentile and small‐for‐gestational‐age <3rd percentile, differences in salivary uric acid levels were insignificant. Conclusions Elevated levels of salivary uric acid precede the onset of preeclampsia, pregnancy‐induced hypertension and preterm delivery. Salivary uric acid may prove to be an early biomarker of hypertensive complications of pregnancy and spontaneous preterm delivery.

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

“…However, their findings were limited by differences in the number UA assessments across study groups and a lack of standardization in the timing of biospecimen collections (14). A recent prospective examination of repeated measurements of salivary UA (sUA) across pregnancy found sUA levels predicted preeclampsia and pregnancy-induced hypertension (13). However, this study did not consider potential confounding variables, such as obesity and race/ethnicity, and only examined sUA levels in the early morning (13).…”

“…Serum UA levels, particularly in early pregnancy, have been associated with increased risk of developing GDM (8)(9)(10)(11). High concentrations of serum UA during pregnancy have also been associated with high BP and preeclampsia, as well as related poor birth outcomes such as lower birth weight and earlier gestational age at birth (12)(13)(14)(15)(16)(17)(18)(19). Further, among women with GDM or hypertensive disorders in pregnancy, UA levels may help identify a subset of women at particularly high risk of poor maternal or fetal outcomes, such as preterm birth, small for gestational age, and preeclampsia (16,(20)(21)(22)(23).…”

“…High levels of UA in early pregnancy, and changes from early to late pregnancy, may be important predictors of GDM and hypertensive disorders (9-11, 13, 14, 39). However, few studies have examined UA longitudinally across pregnancy (see (13,14) for exceptions), and those that have measured UA across gestation vary in the timing and frequency of assessments. For example, Powers and colleagues examined serum UA multiple times across gestation to evaluate patterns of UA across pregnancy among healthy women and those with preeclampsia (14).…”

“…A recent prospective examination of repeated measurements of salivary UA (sUA) across pregnancy found sUA levels predicted preeclampsia and pregnancy-induced hypertension (13). However, this study did not consider potential confounding variables, such as obesity and race/ethnicity, and only examined sUA levels in the early morning (13). Diurnal variation in UA levels, and how variability in UA levels across the day may be related to health, represents another significant gap in our understanding of UA's role during pregnancy.…”

Salivary Uric Acid: A Noninvasive Wonder for Clinicians?

“…A number of studies conducted recently have established the importance of salivary uric acid estimation and its potential to replace other urine and blood tests [ 6 ]. Presently, laboratories worldwide are using saliva majorly for the estimation of immunoglobulin A, cortisol, testosterone, and drugs [ 7 ].…”