DIFFERENTIAL-EFFECTS OF PERINATAL HYPOXIC RISK ON EARLY DEVELOPMENTALOUTCOME - A TWIN STUDY

The goal of this twin study was to explore the effects of perinatal ne urobiological risk on 2 dimensions of early developmental outcome: men tal and motor. The hypothesis was that the performance of the twin con sidered to be at higher risk for hypoxic insult would fall short of th at exhibited by the lower risk co-twin. Twin discordance was establish ed on 2 indirect indices of perinatal hypoxic risk: the Apgar score an d the degree of need for neonatal respiratory oxygen support. The earl y outcome measures, the Bayley Scales of Infant Development (BSID), me ntal (MDI) and psychomotor (PDI) components, were obtained far 76 infa nts. Fifty-six infants were from 28 pairs of twins who were determined to be discordant, and 20 infants from 10 additional pairs who were fo und to be nondiscordant, on the risk indices. Although the average dif ferences between the discordant co-twins in Apgar scores and in need f or oxygen supplementation were small, the twins who were at higher ris k for hypoxic insult had a significantly lower MDI compared to their l ower risk co-twins. This within-pair effect was somewhat greater for p remature, same-sex twins. No intrapair differences associated with ris k level were found on the PDI. We conclude that early development of m ental skills appears more sensitive to perinatal hypoxic risk than gro ss motor development when both outcome domains are defined according t o the BSID.