Maternal and neonatal risk factors for mental retardation: defining the 'at-risk' child.

OBJECTIVE: To determine how mental retardation at age seven is related to certain maternal, perinatal, and neonatal characteristics.
METHOD: A sample of 35,704 children followed from the prenatal period to age 7 years in the Collaborative Perinatal Project provided data on nine maternal and pregnancy characteristics and 12 neonatal factors.
RESULTS: Low socioeconomic status of the family (SES) accounted for 44-50% of mental retardation and a low level of maternal education accounted for 20%. Other prenatal factors with significantly elevated relative risks, (P < 0.05) were maternal IQ score less than 70, weight gain in pregnancy less than 10 pounds and multiple birth. Maternal anemia in pregnancy accounted for 14% of mental retardation in blacks, and, urinary tract infections accounted for 6% of mental retardation in whites. Significant elevations in relative risk were found for major genetic and post-infection syndromes, CNS malformations, cerebral palsy, seizures, abnormal movements or tone, and low birth weight. Relative risk was also significantly increased with low 1 minute APGAR, primary apnea, and head circumference and length more than 2 SD below average but only in the low SES black subgroup.
CONCLUSION: Early developmental events can be ranked on the basis of the strength of their association with mental retardation and such rankings can be used as a guide for defining risk status in early infancy.