The cohort comprised 71 infants born at less than 32 weeks of gestation who were admitted to the hospital within 28 postnatal days between September 2022 and September 2023. The median gestational age was 28.4 weeks and the median birth weight was just 1,100 grams, underscoring how vulnerable this population is from the moment of birth. In-hospital mortality was 22.5 percent, with 16 of the 71 enrolled infants dying before discharge, a figure that reflects the considerable survival challenges faced by babies born this early even in a major pediatric referral center. Among the survivors, the study tracked not only developmental outcomes but also growth, using standardized anthropometric references to quantify nutritional status and head growth over time.

Developmental screening was performed at two key time points: 6 months corrected age, with 51 infants assessed, and 12 months corrected age, with 50 infants assessed. Corrected age, which subtracts the weeks of prematurity from the infant’s chronological age, is the standard convention for evaluating preterm children fairly against developmental milestones. The ASQ-3 results were classified into three tiers: scores within the normal range, a monitor category indicating scores between one and two standard deviations below the mean, and a high-risk or refer category for scores at or below two standard deviations below the mean in any domain. This tiered approach allows clinicians to distinguish children who need immediate referral for comprehensive assessment from those who warrant closer surveillance.

At 6 months corrected age, the results were already concerning. 21.6 percent of the screened infants fell into the high-risk category, and another 21.6 percent were classified as monitor, meaning that more than four in ten babies showed some degree of developmental concern. Gross motor function emerged as the most affected domain, with 17.6 percent of infants scoring in the high-risk range for that domain alone. Gross motor skills, which encompass abilities such as rolling, sitting, and eventually crawling and walking, are often the first to reveal the effects of preterm birth on the developing brain, as motor pathways are among the most sensitive to the disruptions of early extrauterine life and neonatal illness.

By 12 months corrected age, the picture had grown more alarming rather than less. The high-risk screen-positive rate rose to 38.0 percent, the monitor category accounted for 24.0 percent, and only 38.0 percent of the children screened within the normal range. In other words, nearly two-thirds of the surviving preterm infants showed some indication of developmental delay risk as they approached their first birthday. The researchers note that this increase over time may partly reflect the emergence of more complex skills that are harder to achieve for children with early neurological injury, but the trend nonetheless signals that developmental problems in this population are not resolving on their own and may be becoming more apparent as expectations rise.

To address the possibility that some of the observed patterns were artifacts of the specific questionnaire forms used at each age, the investigators performed a within-child z-score analysis. This statistical approach compares each child’s performance across domains relative to their own overall profile, controlling for form-specific measurement differences. The analysis confirmed that gross motor function showed the most robust evidence of persistent delay, independent of measurement variation between questionnaire versions. This finding strengthens the case that motor development is a genuine and persistent area of concern in this cohort, rather than a statistical quirk of the screening instrument.

Growth outcomes told a parallel story of ongoing vulnerability. Extrauterine growth restriction, defined using Fenton 2013 references at discharge, was present in 19.6 percent of the infants, indicating that nearly one in five babies left the hospital significantly smaller than expected for their age. After discharge, the proportion of children who were underweight, defined as a weight-for-age z-score below two standard deviations under the WHO 2006 reference, stood at 13.7 percent at 6 months corrected age and remained at 12.0 percent at 12 months. More strikingly, microcephaly, defined as a head circumference z-score below two standard deviations, increased from 11.8 percent at 6 months to 22.0 percent at 12 months corrected age. This near-doubling of microcephaly prevalence suggests that head growth, which serves as a proxy for brain growth, was failing to keep pace in a growing subset of children, a pattern that often accompanies or predicts neurodevelopmental impairment.

The study also identified specific clinical risk factors associated with worse developmental outcomes. Using univariate Firth logistic regression models, which are well suited to small samples and rare events, the researchers found that gestational age below 28 weeks and bronchopulmonary dysplasia of any grade were each associated with approximately fivefold higher odds of high-risk ASQ-3 classification. Bronchopulmonary dysplasia, a chronic lung disease of prematurity, reflects prolonged oxygen dependence and is a well-established marker of cumulative neonatal illness severity. Both factors retained clinically relevant adjusted effect sizes with adequate calibration, meaning that even after accounting for other variables, being born extremely early or developing chronic lung disease remained strong predictors of developmental concern. These findings align with a large body of international evidence linking extreme prematurity and severe neonatal morbidity to adverse neurodevelopmental trajectories.

The implications for clinical practice in resource-limited settings are significant. The authors argue that early, structured follow-up should integrate ASQ-3 screening, targeted physiotherapy referral, and close monitoring of head growth and nutritional status as core components of neonatal care pathways. Because the ASQ-3 is a parent-completed tool, it is relatively inexpensive and feasible to administer at scale, making it particularly attractive in settings where access to developmental pediatricians and formal assessment services is limited. The monitor category provides a built-in mechanism for prioritizing scarce follow-up resources, directing intensive intervention toward children at highest risk while maintaining surveillance over those with milder concerns.

The study’s single-center design and modest sample size warrant caution in generalizing the exact prevalence figures to other populations, and the authors acknowledge that screening tools like the ASQ-3 identify risk rather than provide definitive diagnoses. Nonetheless, the research fills an important gap in the literature by providing longitudinal, parent-completed screening data from Vietnam, a country where neonatal care has improved substantially but where structured developmental follow-up programs remain uneven. As survival rates for very and extremely preterm infants continue to rise in low- and middle-income countries, the demand for early identification and intervention services will only intensify. This study makes a compelling case that investing in structured screening and referral systems is not merely desirable but essential if the gains in survival are to be matched by gains in the quality of life that surviving children experience.

Subject of Research: Preterm birth and neurodevelopmental screening in low-resource settings

Article Title: Developmental delay risk in very and extremely preterm infants at 6 and 12 months corrected age: a prospective cohort study using ASQ-3 in Vietnam

Article References: Ho, T. T. B., Nguyen, M. T., & Nguyen, T. T. (2026). Developmental delay risk in very and extremely preterm infants at 6 and 12 months corrected age: a prospective cohort study using ASQ-3 in Vietnam. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07779-2

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07779-2

Keywords: preterm birth, developmental delay, ASQ-3, corrected age, neurodevelopmental screening, Vietnam, bronchopulmonary dysplasia, extrauterine growth restriction, microcephaly, low- and middle-income countries, Developmental, delay