<prompt> Microsomia is defined as -Bih weight below 90th percentileBih weight below 10th percentileBih weight below 20th percentileBih weight below 50th percentile  <response>: Ans. is b i.e., Bih weight below 10 percentile Microsomia means small for date baby, i.e. newborn baby with a bih weight less than 10th percentile. 