<prompt> Microsomia is defined as:Birth weight below 90th percentileBirth weight below 10th percentileBirth weight below 20th percentileBirth weight below 5th percentile  <response>: b. Birth weight below 10th percentileRef: Nelsons 20e p 789-791, Ghai 8e p 124-125Microsomia is another name for a small for date SFD or small for gestational age SGA baby.SFD baby is a baby whose birth weight is less than 10th centile of expected according to the gestational age. 