Bilateral hand use during infancy in very low birth weight infants.

[Purpose] To determine the age in months of bilateral hand use during the infancy period of preterm infants with birth weight <1,500 g. [Participants and Methods] This retrospective, observational study included 57 infants with no neurodevelopmental handicaps (average weight at birth 963.2 ± 298.2 g, gestational age 28.4 ± 3.1 weeks), who were transferred to the neonatal intensive care unit at a medical center in Japan between 2010 and 2014. The patients were classified into two groups based on weight at birth: 32 infants with birth weights <1,000 g (Group A) and 25 with birth weights between 1,000 and 1,499 g (Group B). Data on the ages at which bilateral hand use was attained ("playing with both hands together", "transferring a toy between the two hands", and "grasping two toys, one in each hand") were collected from the respective medical records and compared between the two groups. [Results] Significantly delayed bilateral hand use was detected in Group A compared to that in Group B for "transferring a toy between the two hands" (90th percentile, 7.2 months compared to 6.3 months). For the other two items, no differences were detected between the two groups. [Conclusion] The development of bilateral hand use during infancy differed among infants with very low birth weight and was delayed in the group with a lighter birth weight group.