<prompt> Most common cause of abortion in first trimester is-GeneticMaternalImmunologicAnatomic abnormalities  <response>: Ans. is a i.e., GeneticCauses of first trimester abortiono Genetic: Majority 50 of the early miscarriages are due to the chromosomal abnormality of the conceptus.Autosomal trisomy is the commonest cytogenetic abnonnality. Trisomy 16 is the most common.o Endocrine and metabolic 10 - 15Luteal phase defect, deficient progesterone, thyroid abnormalities, diabetes mellitus. o Anatomical abnormalities 10 - 15Cervico - uterine factors mostly related to second trimester abortion - cervical incompetence and congenital malformation of the uterus.o Infections: 5Can cause early as well as late abortions.o Immunological disorders 5- 10 o Blood group incompatibilityo Premature rupture of membraneso Environmental: Cigarette smoking, alcoholo Unexplained. 