Very low-birthweight preterm infants walk later than term infants, but most are walking by 18 months.

Questions: Do very low-birthweight (VLBW) preterm infants attain walking later than term infants? What factors predict delayed walking attainment in very low-birthweight preterm infants? Design: Inception cohort study with 18month follow-up. Setting: University hospital in Taiwan. Patients: Ninety-six VLBW preterm infants were recruited from the neonatal intensive care unit. Inclusion criteria included: gestational age < 37 weeks, birth weight < 1501g, absence of chromosomal or other genetic abnormalities. A comparison group of 82 term infants, born by uncomplicated, spontaneous vaginal delivery, was also studied. Follow-up was 100% at 18 months for preterm infants and 89% for term infants. Assessment of prognostic factors: Perinatal and sociodemographic data were collected from medical records. Main outcome measures: Parents monitored and recorded the date when the infant could take five successive steps without support. A research assistant made monthly phone calls in the age period 9-18 months to ask questions on motor status and age of walking. Clinical tests of motor function were performed by physiotherapists using the Alberta Infant Motor Scale at six, nine, 12 and 18 months. In 95% of infants, the parent’s record corresponded with the telephone responses and clinic motor tests. In cases of disagreement the parent’s report was considered the age of walking attainment. Main results: Eighty-five VLBW preterm infants (89%) attained walking by 18 months whereas all term infants attained walking by 18 months. The median age of walking attainment was greater in the preterm infants (14 months) than in the term infants (12 months; p < 0.001). Univariate risk factors for failure to attain walking by 18 months (with risk ratios and 95% CI) included: gestational age < 30 weeks (2.67; 1.67 to 4.27), birth weight < 1001g (2.25; 1.40 to 3.60), intraventricular haemorrhage Grade III-IV (5.32; 1.30 to 21.74), duration of ventilation > 7 days (3.64; 2.21 to 5.95), duration of oxygen use > 28 days (2.92; 1.82 to 5.00) and Stage III-IV retinopathy of prematurity (7.25; 2.83 to 18.52). Conclusion: Very low-birthweight preterm infants attain walking, on average, about two months later than term infants. The risk of failure to walk at 18 months is nonetheless low (11%). Failure to attain walking by 18 months in VLBW preterm infants is associated with low gestational age, prolonged ventilation, severe retinopathy of prematurity and severe intraventricular haemorrhage. Commentary