Accommodation of low birth weight babies in dedicated and convertible rearward facing child restraint systems

Optimal crash protection for child passengers requires an appropriate restraint for the size of the child. Current infant restraint systems are designed to fit babies of normal birth-weight; however some babies are discharged from hospital at just over half of this weight. Almost 20% of babies discharged from the special care nursery at one Sydney hospital are < 2.2kg. While it is likely that these lower birth weight (LBW) infants may be poorly accommodated in many child restraints on the market, this has not been studied previously. A cohort of 90 new born infants (median weight 2.4kg) within 1 week of discharge was recruited from the postnatal ward and special care nursery of a Sydney hospital from July 2012 to August 2014. The infants were placed in a selection of 4 infant restraints (2 dedicated and 2 convertible rearward facing restraints), and a subset was also placed in a restraint designed to meet the newly adopted LBW design requirements of AS1754. Assessment of harness fit demonstrated that the restraint designed for LBW babies provided superior accommodation. However, accommodation for LBW infants in the other restraints was generally poor. For LBW infants, harness buckle position was worse in the dedicated restraints than convertible restraints (p=0.03) but shoulder strap width was better in convertible restraints (p=0,04). Comparison of infant anthropometry with shoulder and crotch strap geometry in all restraints identified areas for improving AS1754 LBW requirements. Parents of LBW infants should be encouraged to use restraints specifically designed to accommodate small infants