Intrauterine twin environment and genetic factors subliminally affecting general movements in preterm infants.

BACKGROUND: Understanding background factors is beneficial for interpreting general movements (GMs). This study examines the factors involved in preterm-writhing GMs by comparing twins and singletons.

METHOD: The subjects were 107 infants cared for at Oita University. The cohort consisted of very-low-birth-weight infants, including twins with a birth weight < 2000 g. The median gestational age (GA) was 29 weeks 1 day. The subjects consisted of 75 singletons, 32 twins (16 pairs), 20 monochorionic twins (M-twins), and 12 dichorionic twins (D-twins). GMs were scored according to the GMs optimality score (GMOS) and integrated into 6 items: the quality, neck-trunk and space, amplitude-speed, rotation, onset-offset and cramped, and tremulous score at 32-34 weeks, 35-36 weeks, and 37-42 weeks' GA. A hierarchical cluster analysis was performed using integrated GMOS, and the characteristics of clusters were examined according to clinical backgrounds.

RESULTS: Three clusters were identified. Cluster 1 was characterized by good-quality GMs, cluster 2 by a poor repertoire but optimal space and rotatory components, and cluster 3 by overall poor-quality GMs, respectively. The mean GMOSs were 36.6, 31.8 and 24.3 in clusters 1, 2, and 3, respectively. There were no marked differences in proportions within clusters with respect to sex and twins. Small-for-gestational age (SGA) was significantly more frequent in cluster 3 at 32-34 weeks' GA than in other clusters. Perinatal brain injury had a significantly lower proportion in cluster 1 and a higher proportion in cluster 3 at 35-36 weeks' GA and 37-42 weeks' GA. M-twin pairs tended to belong to the same clusters at 35-36 weeks' GA.

CONCLUSION: Preterm writhing GMs are associated with SGA and perinatal brain injury. Cluster matching in M-twins suggests that certain genetic factors may substantially influence GMs.