<prompt> WHO definition of aboion isPregnancy termination or loss before 12 weeks of gestationPregnancy termination or loss before 20 weeks of gestationPregnancy termination or loss before 22 weeks of gestationPregnancy termination or loss before 24 weeks of gestation  <response>: The National Center for Health Statistics, the Centers for Disease Control and Prevention, and the World Health Organization all define aboion as pregnancy termination or loss before 20 weeks gestation or with a fetus delivered weighing 500 g.Reference: Williams Obstetrics; 25th edition; Chapter 18; Aboion 