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. 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. 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. 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. © 2020 Nordic Federation of Societies of Obstetrics and Gynecology.