title: Maternal and fetal blood ammonia concentrations in normal term human pregnancies.
abstract: BACKGROUND
  The current evidence on the primary source of ammonia production in the human fetoplacental unit is potentially misleading.
  
  
  OBJECTIVE
  The aim of the present investigation was to determine the concentration of ammonia in human maternal and fetal blood at birth and to compare them with published data in late gestation sheep.
  
  
  METHODS
  In 12 normal human pregnancies, umbilical arterial and venous and maternal venous blood was sampled, and whole blood ammonia concentrations were measured. Data from 12 pregnant sheep and fetuses from our previous studies were utilized for comparison.
  
  
  RESULTS
  The human fetus at delivery has higher concentrations of ammonia (60-80 microM) than the late gestation fetal lamb (25-35 microM). In the human, the arterial umbilical ammonia concentration exceeds the venous umbilical concentration, indicating a net ammonia production by fetal tissues. In sheep, the venous umbilical ammonia concentration exceeds the arterial umbilical concentration, indicating the net placental ammonia production.
  
  
  CONCLUSIONS
  In contrast to fetal lambs, human fetuses exhibit a net production of ammonia, which may reflect differences in biologic state or a species difference.
authors.affiliation: Department of Gynecology, Medical University of Białystok, Białystok, Poland. jozwikmc@obgyn.edu.pl
authors.forename: Maciej
authors.initials: M
authors.lastname: Jóźwik
authors.forename: Marcin
authors.initials: M
authors.lastname: Jóźwik
authors.forename: Bartosz
authors.initials: B
authors.lastname: Pietrzycki
authors.forename: Marcin
authors.initials: M
authors.lastname: Chojnowski
authors.forename: Cecilia
authors.initials: C
authors.lastname: Teng
authors.forename: Michał
authors.initials: M
authors.lastname: Jóźwik
authors.forename: Frederick C
authors.initials: FC
authors.lastname: Battaglia
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood*; D000818:Animals; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D012016:Reference Values; D012756:Sheep / Q000097:blood; D013045:Species Specificity; D014469:Umbilical Arteries; D014471:Umbilical Veins
chemical_list: D000641:Ammonia