MATERNAL SERUM URIC-ACID LEVELS IN TWIN GESTATIONS

Objective: To establish normative values of serum uric acid levels in women with twin gestations and to compare maternal serum uric acid levels of twins and singletons, stratified by the presence or absence of preeclampsia. Methods: Sixty-seven normotensive and 16 preeclamptic women with twin gestations, who had no underlying chronic hypertension or renal insufficiency, had serum uric acid levels measured on admission to the labor and delivery unit. These levels were compared with those of 83 normotensive and 10 preeclamptic singleton gravidas admitted to the same unit. A receiver operating characteristic (ROC) curve was used to determine the optimal maternal serum uric acid cutoff value for twin gestations and to compare this value with that of singleton gestations. Results: Women with non-preeclamptic twin pregnancies had significantly higher mean (+/- standard deviation) serum uric acid concentration than women with non-preeclamptic singleton pregnancies (5.4 +/- 1.6 versus 4.7 +/- 1.2 mg/dL, respectively, P = .001). Gravidas with twin gestations complicated by preeclampsia had significantly higher serum uric acid levels than their preeclamptic singleton counterparts (7.7 +/- 1.3 versus 5.9 +/- 1.1 mg/dL, respectively, P = .001). Using a ROC curve, we determined that a maternal serum uric acid level of 6.5 mg/dL appeared to be the optimal cutoff for identifying preeclampsia in twin gestations, with a sensitivity of 94% and specificity of 78%. Conclusion: With or without preeclampsia, women carrying twins have significantly higher serum uric acid levels than their singleton counterparts, which suggests a need for separate normative values for twin gestations. We propose that a serum uric acid level of 6.5 mg/dL or greater be used to identify those women with twin gestations who are at higher risk for preeclampsia.