Developmental delay should be suspected if the development quotient(DQ) is below 70%. It is calculated as: DQ= Development age/Chronological age * 100 In preterm infants, the corrected age rather than postnatal age is used till two years of age. For example, a child born at 32 weeks gestation (gestational age) seen at 12 weeks of age (postnatal age), should be considered as a 4-week old (corrected age) child. Ref: Ghai essential Pediatrics 9th edition Pgno: 50