<prompt> MC cause of abortion in first trimester is, defect in:PlacentaUterusEmbryoOvarian  <response>: Ans. is c, i.e. EmbryoRef. Dutta Obs. 7e, p 159, 160; Williams Gynae 1e, p 138As explained earlier most common cause of abortion in first trimester are chromosomal abnormalities involving the zygote or embryo. 