Relationship between maternal thyroxine levels during pregnancy and memory function in childhood.

Two investigations are reported into the memory functions of a group of subjects for whom information on maternal thyroxine (T4) levels during pregnancy is available. The first study made when the subjects were aged 14-15 years examined forward and backward memory span. No relationship between maternal T4 levels and capacity of the short-term store, measured as length of forward memory span, was found. Backward memory span, which involves performing a mental operation on the material held in store, was found to be associated with maternal T4 level. The second study, made when the subjects were aged 16-17 years, found a relationship between maternal T4 levels during pregnancy and memory for serial position. Findings are discussed in terms of the role of maternal thyroxine in fetal brain development.