Unstable longitudinal motor performance in preterm infants from 6 to 24 months on the Bayley Scales of Infant Development--Second edition.
Raw Bayley motor scores give a clear growth line for preterm infants; norm-corrected labels bounce around and mislead.
01Research in Context
What this study did
The team followed 61 preterm babies every six months from months. Each visit they gave the Bayley Scales of Infant Development motor section. They recorded both the raw number of items passed and the norm-corrected score that compares the child to same-age peers.
They wanted to know which number stays steady over time and which one jumps around.
What they found
Raw motor scores crept up in a straight line as the babies got stronger. Norm-corrected categories swung wildly: a child labeled "delayed" at 12 months could be "average" at 18 months and then "delayed" again at 24 months.
The corrections added noise, not clarity.
How this fits with other research
Eussen et al. (2016) extend our finding. They show Bayley-III scores under 3.5 years do predict later language and cognition in toddlers with ASD. Their message: low raw scores matter, so intervene early.
Zhou et al. (2018) synthesis includes 21 motor studies and finds most designs are weak. Our paper gives them one clear takeaway: use raw scores to judge progress, not shifting norm bins.
Morrison et al. (2017) look at parent report versus direct testing. They found parents and testers mostly agree on fine-motor items. Pair their result with ours: collect raw item counts from both sources and skip the norm tables.
Why it matters
When you track a preterm baby in early intervention, plot the raw Bayley motor items passed. Ignore the percentile band that flips between visits. A steady upward line means the plan is working; a flat line tells you to adjust teaching or refer out. Share this graph with parents so they see real progress instead of confusing labels.
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Join Free →Graph the child’s raw Bayley motor items across visits; teach the next skill on the sequence if the line is climbing, adjust the program if it plateaus.
02At a glance
03Original abstract
Preterm birth increases the risk for neurologic and developmental disabilities and therefore long-term follow-up is important. This prospective follow-up study aims to describe longitudinal motor performance in preterm infants from 6 to 24 months and to detect the influence of risk factors on motor performance trajectories. We included preterm infants (n=348) with a gestational age of ≤32 weeks. The Bayley Scales of Infant Development, 2nd edition (BSID-II) Motor Scale and the Behaviour Rating Scale were recorded at the corrected ages of 6, 12 and 24 months. The Motor Scale raw score was the dependent variable in random coefficient analysis for risk factors in the cohort if infants with cerebral damage were in- and excluded. The raw score increased, showed the highest correlation (rp=0.48-0.67) and was more stable than the PDI and its classification. Fifteen percent of the infants had a stable classification, while 45% changed one class. Male sex and intra-ventricular haemorrhage (IVH) lowered the raw scores. Higher motor quality scores and height increased the raw scores, while the influence of maternal education varied at different time points. Removal of infants with cerebral damage from the cohort did not change the risk factors. The results showed that the raw score trajectories were more stable, but after corrections for norm data, the measurements became highly unstable. This is clinically important when reporting results to parents, guiding intervention and in randomised trials. The risk factors predominantly influenced the level of motor performance raw scores. Maternal education additionally influenced the trajectory and should be included in randomisation procedures.
Research in developmental disabilities, 2011 · doi:10.1016/j.ridd.2011.03.026