title: Changes in activated protein C resistance during normal pregnancy.
abstract: OBJECTIVE
  The objective of this study was to determine the changes in activated protein C resistance that occur during normal pregnancy.
  
  
  METHODS
  In this cross-sectional study activated protein C was measured in 128 women with normal pregnancies in the first, second, and third trimesters and in nonpregnant control subjects with 24 to 39 women in each group. In addition, factor V, factor VIII, free protein S, and functional protein C were measured and correlated with activated protein C levels. Polymerase chain reaction for factor V Leiden mutation was performed.
  
  
  RESULTS
  There was a significant fall in the activity of activated protein C in the second and third trimesters of pregnancy (p < 0.05). This was related to increased factor VIII and decreased free protein S levels (p = 0.002, R2 = 0.20). The prevalence of the factor V Leiden mutation was 7.3%.
  
  
  CONCLUSIONS
  Resistance to activated protein C is increased in the second and third trimesters of pregnancy. This is related to the alterations in other coagulation proteins, a phenomenon normally occurring during pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, University of Ottawa, Ontario, Canada.
authors.forename: M C
authors.initials: MC
authors.lastname: Walker
authors.forename: P R
authors.initials: PR
authors.lastname: Garner
authors.forename: E J
authors.initials: EJ
authors.lastname: Keely
authors.forename: G A
authors.initials: GA
authors.lastname: Rock
authors.forename: M D
authors.initials: MD
authors.lastname: Reis
mesh_terms: D000328:Adult; D001779:Blood Coagulation Factors / Q000032:analysis / Q000378:metabolism; D003430:Cross-Sectional Studies; D005165:Factor V / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D005169:Factor VIII / Q000032:analysis / Q000378:metabolism; D005260:Female; D006801:Humans; D009154:Mutation; D010314:Partial Thromboplastin Time; D016133:Polymerase Chain Reaction; D011247:Pregnancy / Q000097:blood* / Q000502:physiology*; D011261:Pregnancy Trimester, First / Q000097:blood; D011262:Pregnancy Trimester, Second / Q000097:blood; D011263:Pregnancy Trimester, Third / Q000097:blood; D011486:Protein C / Q000032:analysis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D017293:Protein S / Q000032:analysis / Q000378:metabolism; D013917:Thrombin / Q000032:analysis / Q000502:physiology; D018180:Thrombomodulin / Q000032:analysis / Q000502:physiology
chemical_list: D001779:Blood Coagulation Factors; D011486:Protein C; D017293:Protein S; D018180:Thrombomodulin; D005165:Factor V; D005169:Factor VIII; D013917:Thrombin