Infants born after a threatened preterm labour (TPL infants) are at high risk of autism spectrum disorder (ASD). Studying this population may provide insight on the pathophysiological underpinnings of this condition. This study aimed to (i) ascertain the presence and autistic symptom load in TPL infants aged age 30 months relative to non-TPL infants, regardless of preterm birth; (ii) explore the association between early (at 6 months) psychomotor development and temperament features with the autistic symptom load of TPL infants at age 30 months and (iii) examine the association among perinatal risk factors for ASD development with the autistic symptom load of TPL infants at age 30 months. A group of 111 mother-infant pairs recruited at TPL diagnosis and a group of 47 healthy mother-infant controls completed the follow-up. Irrespective of preterm birth, TPL infants showed higher autistic symptom load at age 30 months than non-TPL infants. TPL infants presented poorer communication and problem-solving skills, reduced smiling and laughter, and greater vocal reactivity at age 6 months, predicting higher autistic symptom load at age 30 months. Higher levels of anxiety symptoms in TPL mothers after a TPL diagnosis also predicted higher autistic symptom load for the infants at age 30 months. These results suggest that TPL infants may be an undescribed cluster, with features that differentiate them from other "at-risk" populations. These findings support the need for routine assessment of TPL infants and screening of anxiety symptoms in mothers.
Keywords: Anxiety; Autistic symptom load; Neurodevelopmental disorders; Pregnancy; Psychomotor development; Temperament.
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