Arginine Vasopressin is not elevated in Early Pregnancy Loss

Abstract

BackgroundAdministration of arginine vasopressin (AVP) has been previously shown to influence myometrial contractility during the first trimester of pregnancy in women who were undergoing a planned therapeutic abortion. Consequently, it was hypothesized that AVP may play a role in early spontaneous pregnancy loss. AVP is made in a 1:1 molar ratio with copeptin; thus, copeptin can be used as a surrogate measure of AVP. While early pregnancy loss is likely a multifactorial problem, we sought to fill the gap in knowledge of the causes of using pre‐collected samples from pregnancies that subsequently underwent spontaneous abortion and matched controls.MethodsA retrospective case control study was performed using plasma samples from the Maternal Fetal Tissue Bank (IRB# 200910784) at the University of Iowa Hospitals & Clinics. Whole blood samples were collected (ACD‐A tubes, Becton Dickinson) at confirmation of pregnancy appointments in which a viable pregnancy was detected by ultrasound (6‐10 weeks gestation). Samples were processed and plasma aliquots were snap frozen and stored at ‐80oC until analysis. Control samples (N=67) from viable, healthy pregnancies were matched by gestational age, race, ethnicity, and body mass index to cases (N=123). Copeptin was measured by an automated immunoassay (Brahms KRYPTOR) and total protein concentration via a bicinchoninic acid (BCA) protein assay (Pierce). Copeptin concentrations were normalized to total protein in samples. Continuous variables were analyzed by T test.ResultsNo significant differences were detected in plasma samples that were collected while the pregnancies appeared viable. Copeptin was 7.2 +/‐ 6.0 mg/dL in case plasma samples and 6.0 +/‐ 3.4 mg/dL in control plasma samples (P=0.066). It is unclear if vasopressin increases acutely prior to the occurrence of spontaneous abortion.ConclusionThese results suggest that vasopressin cannot be used to identify pregnancies at risk of early loss at the time of pregnancy confirmation.