title: First-trimester uterine artery resistance and maternal serum concentration of asymmetric dimethylarginine.
abstract: OBJECTIVE
  Maternal serum levels of asymmetric dimethyl-arginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase, are known to be increased in pregnant women with high-resistance placental circulation in the second trimester. The aim of the present study was to investigate the relationship between uterine artery resistance and maternal serum ADMA concentrations in the first trimester.
  
  
  METHODS
  Doppler ultrasound examination of the maternal uterine arteries was performed at 10-14 weeks' gestation. High resistance was defined as bilateral uterine artery notches and a mean resistance index > 95th centile. Control cases were defined as those presenting with no notches and a mean resistance index < 95th centile. ADMA concentrations were measured in maternal serum.
  
  
  RESULTS
  Forty singleton pregnancies were examined, 21 with high uterine artery resistance and 19 controls. Three cases of pre-eclampsia occurred, all in the high-resistance group. The mean (SD) maternal serum ADMA concentration was 0.78 (44%) and 0.93 (56%) micromol/L in the high-resistance and control groups, respectively (P = 0.17). There was no statistically significant correlation between maternal serum ADMA and uterine artery resistance index (rho = - 0.15, P = 0.36).
  
  
  CONCLUSIONS
  No significant difference was found in maternal serum ADMA between pregnancies with first-trimester high-resistance uterine artery blood flow and controls. While second-trimester circulating ADMA may have a direct link with maternal endothelial function, in the first trimester the effect of ADMA may be mainly evident at the placental level, without consequently affecting maternal circulating concentrations of the substance.
authors.affiliation: Fetal Medicine Unit, Division of Obstetrics and Gynaecology, Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London, UK. federico.prefumo@libero.it
authors.forename: F
authors.initials: F
authors.lastname: Prefumo
authors.forename: B
authors.initials: B
authors.lastname: Thilaganathan
authors.forename: G S
authors.initials: GS
authors.lastname: Whitley
mesh_terms: D000328:Adult; D001120:Arginine / Q000031:analogs & derivatives* / Q000097:blood; D001158:Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006801:Humans; D011225:Pre-Eclampsia / Q000175:diagnosis*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D018608:Ultrasonography, Doppler; D014599:Uterus / Q000098:blood supply* / Q000000981:diagnostic imaging; D014655:Vascular Resistance
chemical_list: C018524:N,N-dimethylarginine; D001120:Arginine