Background: Ovarian steroid action is not limited to the gonadalpituitaryhypothalamic axis. A recent pre-clinical investigation by Sutcliffe et al. (2007) suggests female sex steroids influence learning and memory strategies. However, data from human trials involving various hormone replacement regimens and assessment of memory in pregnancy appear equivocal.
Pregnancy allows overriding of regulatory feedback loops leading to elevation of endogenous serum hormone levels. Oestrogen seems to have a modulating or protective role. However at high concentrations, oestradiol metabolism leads to redox cycling and formation of free radicals, with toxic effects in the hippocampus, possibly reducing some memory functions. The aim of this investigation is to increase our understanding of the effects of sex steroids on memory and attention during pregnancy.
Methods: Participants (n=40) are being tested pre-conceptually, each trimester and postnatally. Non-pregnant controls are tested using the same methodology. Demographic, mood and general health data are being collected at each session. The Cambridge Neuropsychological Test Automated Battery (CANTAB), a non-invasive computer based task, is being used to examine different cognitive domains. Verbal intellectual ability is also being assessed. Plasma hormone levels are obtained at each session for later analysis. The study received ethics approval prior to recruitment.
Results: Pregnant participants during the first trimester performed significantly less well in the delayed matching to sample test (DMS-% correct), pregnant group mean 78% (S.E. 1.8), control mean 85% (S.E. 1.5), (P=0.003) and (DMS-probability of an error following an error) pregnant mean 0.17 (S.E. 0.01), control mean 0.07 (S.E. 0.02), P=0.03. There were no other statistically significant differences between groups.
Conclusion: Initial data support the hypothesis that pregnancy adversely affects performance of certain cognitive tasks, specifically simultaneous and short term visual working memory, illustrated by a deficit on the DMS task, the significant finding in terms of probability error may indicate emotionality or a memory processing deficit.
Sutcliffe J, Marshall KM and Neill JC. (2007). Influence of gender on working and spatial memory in the novel object recognition task in the rat. Behav Brain Res 177 117125.