Cognitive and verbal development of discordant twins without neurological morbidity

Abstract

The aims of this longitudinal study are to investigate the cognitive and verbal development of discordant twins without neurological morbidity. Twenty pairs (40 infants) of discordant twins (discordance range 15–41%) were examined. A follow‐up study was carried out of 11 selected pairs (22 infants), with biological and cognitive measures at birth, at 1 year, at 2 years and at 4 years. Results show that biological growth differences (weight, height and head circumference) tended to disappear after the age of 2 years. Significant differences were found in cognitive and verbal skills between the larger and smaller co‐twins at all ages. When the twins were small for gestational age, and were close to very low birth weight, together with severe discordance, their cognitive and verbal scores were consistently below the range of normality. In conclusion, the differences between the larger and smaller co‐twins appear to persist up to 4 years of age, with respect to cognitive and verbal skills. A possible additive effect of biological risk factors that accumulated in the severe discordances was observed, which appeared to increase the probability of smaller co‐twins suffering delayed cognitive and verbal development.

Acknowledgments

This work was financed in part by the Spanish Ministry of Education and Science through Project BSO 2002‐10276‐E and Project SEJ2004‐006433/EDUC. We thank the children's parents and the staff of the Paediatrics and Obstetrics and Gynecology Departments of the Virgen de las Nieves Hospital in Granada, Spain for their cooperation.