Timed induction of in utero thrombocytopenia. (A) Experimental scheme: mice were injected with anti-GP1Bα or IgG control antibodies between E10.5 and E17.5 and analyzed at 6 hours and 48 hours after injection for platelet numbers and hemorrhage phenotypes. (B) Quantification of circulating platelets as a percentage of peripheral blood at 6 hours after injection at E10.5 to E17.5. (C) Images of embryos 6 hours after treatment (E12.5: IgG n = 12, GP1Bα n = 15; E14.5: IgG n = 18, GP1Bα n = 17; E16.5: IgG n = 14, GP1Bα n = 12; E17.5: IgG n = 16, GP1Bα n = 8). Scale bars, 1 mm. (D) Circulating platelets 48 hours posttreatment. (E) E10.5 to E16.5 embryos 48 hours and E17.5 embryos 24 hours posttreatment (E10.5: IgG n = 16, GP1Bα n = 8; E12.5: IgG n = 12, GP1Bα n = 17; E14.5: IgG n = 17, GP1Bα n = 16; E16.5: IgG n = 18, GP1Bα n = 14; E17.5: IgG n = 17, GP1Bα n = 14). Scale bars, 1 mm. (B,D) Data are represented as mean 6 SD and analyzed using the Student t test (2-way, unpaired). **** P < .0001. Ab, antibody. Yellow arrows indicate sites of hemorrhage.