<prompt> Which of the following is the most common cause of 1st-trimester abortions :Chromosomal deletionsAneuploidyChromosomal translocationTetraploidy  <response>: Ans- B Aneuploidy Overall most common cause- Aneuploidy Most common cause among Aneuploidy types- Trisomy If both Trisomy and Aneuploidy are mentioned - Aneuploidy is the best answer since Trisomy is a type of Aneuploidy. 