Low weight/length ratio to assess risk of cerebral palsy and perinatal mortality in twins.

The etiology of increased rates of cerebral palsy (CP) in twins is unclear, but likely is associated with growth retardation, which occurs more often in twins. Asymmetric growth restriction, a form of growth retardation, has been found associated with increased rates of perinatal morbidity in infants with normal centile birthweights, and occurs more often in twins. Data from 55,457 infants were evaluated. Associations between twinning, CP, and neonatal mortality were evaluated. Influences of confounding factors, such as prematurity, perinatal depression, and asymmetric growth were assessed. Although twinning was a significant univariate correlate of both CP and neonatal mortality, low weight/length ratio (a marker of asymmetric growth) was a better correlate of both outcomes, and twinning was not significantly associated with either outcome after logistic adjustment for factors such as prematurity, perinatal depression, and low weight/length ratio. Low weight/length ratio occurred more often in twins of advancing gestational age, supporting a hypothesis of competition for nutritional resources as the cause for increased rates of low weight/length ratio in twins as compared with singletons. Asymmetric growth restriction is an important correlate of neonatal morbidity in twins, and should be considered when these factors are assessed in infants from multiple gestations.