Study Outcomes

The primary motor outcome was gross motor development, assessed by using the Peabody Developmental Motor Scale, Second Edition (PDMS-2), instrument.¹⁹ Secondary outcomes were neurologic integrity, evaluated by using the Infant Neurologic International Battery (INFANIB),²⁰ and motor quality, assessed by using the Behavior Rating Scale (BRS) of the Bayley Scales of Infant Development, Second Edition.²¹

The PDMS-2 gross motor dimension at 9 months provides an overall motor quotient derived from 3 subscales (reflexes, stationary, and locomotion). Reflexes reflect automatic reactions to environmental events (eg, righting reflex, parachute reflex). Stationary assesses postural control within the center of gravity and equilibrium (eg, sitting while manipulating a toy, transitioning to sit from prone). Locomotion covers moving from 1 place to another (eg, crawling, sitting to crawling or standing).¹⁹ A Chinese version of the PDMS-2 instrument is routinely used at Peking University First Hospital to track motor development and intervention effects in the rehabilitation clinic. The clinic follows the standard definition of ceiling but also elicits each child’s optimal performance by administering a preset maximum number of items in each subscale based on age. Passed items above ceiling for each subscale are included.²² In our study, only a few infants (31 of 1195) passed items above ceiling, solely in the locomotion subscale. Using scores with passes above ceiling did not affect PDMS-2 outcome in the RCT. Therefore, scoring was preserved as customary at Peking University First Hospital. Because almost all infants were similar in age at the 9-month assessment, the PDMS-2 outcomes are presented as raw scores, controlling for age in days.

The INFANIB assesses infant neurologic integrity. The total score of overall neurologic integrity is a composite derived from 20 items within 5 factors (spasticity/muscle tone, head and trunk control, vestibular function, legs/lower limb function, and French angles [shoulder and hip angles]). Items are scored 1 to 5 (abnormal to normal). Results are expressed as raw subscale and total scores, controlling for age.²⁰

The BRS motor quality factor is based on examiner ratings of infant motor performance. The factor is generated from 8 items related to muscle tone and movement control and quality. Items are rated 1 to 5, with higher values indicating more consistently appropriate behavior.²¹ Results are expressed as the BRS motor quality factor total raw score, controlling for age.

Developmental testing occurred in dedicated rooms at the Maternity and Child Health Care Center. Infants were accompanied by a parent/guardian and given time for adjusting to the setting, frequent breaks, naps, and/or feeding. US and Chinese investigators trained Chinese supervisory personnel, who then jointly trained coders/testers and provided ongoing supervision. Reliability was assessed before and during testing; reliability levels were ≥90%.