title: Antithrombin III activity and platelet count are more likely to decrease in twin pregnancies than in singleton pregnancies.
abstract: BACKGROUND
  It is not known whether antithrombin III activity and platelet count are more likely to decrease in women with twin pregnancies than singleton pregnancies.
  
  
  METHODS
  We enrolled 56 consecutive women with twin pregnancies and 692 consecutive women with singleton pregnancies. Antithrombin III activity and platelet count were determined at 26-31 weeks and again at 32-40 weeks of gestation. Thrombin-antithrombin complex, and plasmin-alpha2 plasmin inhibitor complex were measured simultaneously in some women.
  
  
  RESULTS
  In twin pregnancies, both antithrombin III activity (111 +/- 8.2%) and platelet count (244 +/- 60 x 109/l) at 28.6 +/- 1.0 weeks decreased over time to 91 +/- 12% and 205 +/- 59 x 109/l, respectively, at 35.2 +/- 1.2 weeks; these decreases were significantly greater than in singleton pregnancies. However, a small number of women with singleton pregnancies had a significant decrease in antithrombin III activity in the absence of preeclampsia. The serum thrombin-antithrombin complex was significantly higher in twin pregnancies than in singleton pregnancies (9.7 +/- 4.2 ng/ml vs. 6.7 +/- 4.4 ng/ml, respectively, p < 0.01), and this increase correlated significantly with the decrease in antithrombin III activity in twin pregnancies (r = -0.459, p < 0.001).
  
  
  CONCLUSIONS
  Antithrombin III activity and platelet count show a greater decrease in twin than in singleton pregnancies, perhaps due to a greater increase in thrombin generation.
authors.affiliation: Deparetment of Obstetrics and Gynecology, Jichi Medical School, Tochigi, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Tsunoda
authors.forename: Akihide
authors.initials: A
authors.lastname: Ohkuchi
authors.forename: Akio
authors.initials: A
authors.lastname: Izumi
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsubara
authors.forename: Ikuo
authors.initials: I
authors.lastname: Sato
authors.forename: Hisanori
authors.initials: H
authors.lastname: Minakami
mesh_terms: D000328:Adult; D000990:Antithrombin III / Q000378:metabolism*; D005234:Fatty Liver / Q000097:blood / Q000209:etiology; D005260:Female; D017359:HELLP Syndrome / Q000097:blood / Q000209:etiology; D006801:Humans; D008137:Longitudinal Studies; D010976:Platelet Count; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000097:blood*; D011446:Prospective Studies; D012307:Risk Factors; D014427:Twins; D000979:alpha-2-Antiplasmin / Q000378:metabolism
chemical_list: D000979:alpha-2-Antiplasmin; D000990:Antithrombin III