Published online by Cambridge University Press: 01 August 2014
This report is concerned with the twin births which occurred in the Collaborative Study of Cerebral Palsy, Mental Retardation and Other Neurological and Sensory Disorders of Infancy and Childhood. This is a collaborative endeavor of 14 institutions throughout the US and the National Institute of Neurological Diseases and Stroke, to observe and study factors which affect the parents before a child is born and to relate them to the outcome of pregnancy. To this end, we are following approximately 60 000 pregnant women from the first months of their pregnancy, through labor and delivery and up to the seventh year of the study child's life. The Study population is about 46% White, 46% Negro, 7% Puerto Rican, and the rest a variety of other ethnic groups. The prospective nature of the study makes possible the recording of observations with high accuracy and the avoidance of biases inherent in other types of investigations. These advantages should also be reflected in the collection and evaluation of twin data.