Elevated Urinary Arginine Vasopressin Concentrations during Preeclamptic Pregnancies do not Persist Postpartum

Abstract

BackgroundPreeclampsia (PreE) is a common hypertensive disorder during the second and third trimesters of pregnancy. It is estimated to affect 5‐7% of all U.S. pregnancies; about 400,000 pregnancies per year. PreE leads to increased risks of fetal abnormalities, pregnancy complications, chronic hypertension, and cardiovascular disease. Arginine vasopressin (AVP) plays an important role in controlling osmotic balance, regulating blood pressure, maintaining sodium homeostasis, and functioning of the kidney. AVP is secreted by the hypothalamus as a proprotein with copeptin. Because copeptin and vasopressin are secreted in a 1:1 molar ratio, copeptin measurements can be used a surrogate measure of vasopressin. Our lab has previously demonstrated that vasopressin, as measured by copeptin, is elevated in plasma and urine throughout preeclamptic pregnancies; even before PreE can be clinically diagnosed. However, it is unknown whether urine vasopressin is elevated chronically postpartum. Our objective was to determine whether there is a difference in copeptin concentration between women with and without a history of preeclampsia at 1‐4 years postpartum. We hypothesized that AVP concentrations of subjects who had received a PreE diagnosis would continue to be elevated postpartum.MethodsInclusion criteria for this study (IRB# 201808705) included being 1‐4 years postpartum, not currently pregnant, non‐prisoner, and able to provide informed consent. Women without (N=26; Age 34 +/‐ 3.4 yrs, BMI 25.99 +/‐ 6.34 kg/m2) and with a history (N=25; age 33 +/‐ 4.5 yrs, BMI 30.32 +/‐ 9.12 kg/m2) of preeclampsia in their most recent pregnancy were enrolled. Women fasted, did not smoke, and did not have caffeine for 4 hours prior to their study visit, nor did they have alcohol or exercise for the prior 24 hours. Urine samples were assayed for copeptin concentrations via an automated immunoassay (Brahms KRYPTOR), creatinine concentrations via a QuantiChrom assay, total protein concentrations via a bicinchoninic acid (BCA) protein assay, osmolality by freezing point depression, and specific gravity using a hydrometer.ResultsThere were no differences between the cohorts in race or ethnicity. There was no statistically significant difference in urinary copeptin, as a marker of AVP, in the postpartum period between women with vs. without a history of preeclampsia (4.5 vs. 3.2 mg/dL, P=0.4). No significant differences in copeptin were detected in women without a current hypertension diagnosis (5.49 mg/dL, N=43) and those being treated for hypertension (4.79 mg/dL, N=7, P=0.35).ConclusionsThis study suggests that copeptin, a surrogate measure for AVP, is not chronically elevated in urine after a preeclamptic pregnancy.