Prenatal use of addictive substances and breastfeeding length are robust factors affecting the motor performance of infants aged 0-4 months.

UNLABELLED

Different risk factors are related to motor development in the first months of life; however, prenatal, birth, and contextual risks are usually investigated separately, restraining the ability to understand the weight of each factor on development. This study examined the relationships among prenatal and birth risks and contextual factors on infant motor development (outcome) in the first 4 months of life. This cross-sectional and associative study assessed 662 infants (corrected ages from 34 weeks of post-conceptional age to 17 weeks of post-term). Infants' motor development was assessed using the Test of Infant Motor Performance, hospital records provided biomedical information, and parents completed a demographic questionnaire. The GLM was used; a significant regression model was obtained (  (647) = 57.615, p < .001, AIC = 5965.8, BIC = 6037.8). Breastfeeding length (p < .001) and home opportunities (p = 0.045) positively explained motor development. Further, drug taking (p = 0.018), other(s) children living at home (p = 0.015), and prematurity levels: 32-37 weeks (p < 0.001), 28-32 weeks (p < 0.001), and below 28 weeks (p = 0.008) compared to a term birth negatively explained motor development. The deviance-based R2 indicates that 51% of the variance in the outcome variable is explained by the model predictors. Motor development in the first 4 months of life is influenced by multiple factors; some are more robust than others and require early prevention strategies such as educating mothers about the risks of drug consumption and promoting longer time for breastfeeding.

CONCLUSION

This study highlights that, beyond prenatal substance addiction as a risk factor, extended breastfeeding and enriched home motor environments serve as key protective factors supporting infant motor development.

WHAT IS KNOWN

• Prematurity and prenatal substance exposure are major risk factors for delayed infant motor development. • Breastfeeding and enrich home environment can protect against developmental delays.

WHAT IS NEW

• This study provides robust evidence that cumulative biological and environment risks act synergistically to significantly impair motor development, highlighting the importance of assessing multiple risks factors simultaneously rather than in isolation. • The protective effect of breastfeeding duration remains significant even when accounting for cumulative risks, while enhanced home opportunities for motor stimulation serve as a key modifiable factor mitigating these risks, this is the first study to show how gestational age, prenatal drug exposure, breastfeeding, and home stimulation colectivelly influence infant motor development in a middle-income setting.