Background: Female sex steroids influence learning and memory and the neurobiology of brain regions involved in memory processing such as the hippocampus. Pregnancy allows overriding of regulatory feedback loops leading to substantial elevation of endogenous serum hormone levels, depending on concentration; oestradiol can be either neurologically protective or toxic. This investigation aimed to increase understanding of the influence of sex steroids on memory and attention during pregnancy.
Method: Participants were tested each trimester and at 3 months following birth, some were also tested preconceptually and at 12 months, a non-pregnant control group were also included. Memory and attention were examined using the Cambridge Neuropsychological Test Automated Battery, a computer based assessment tool. Edinburgh Postnatal Depression (EDPS) and General Health Questionnaire12 (GHQ12) scores were collected; the National Adult Reading Test (NART) a measure of verbal intellectual ability was also administered. Steroid/peptide analysis was carried out on a subset of participants plasma. Data were analysed using STATA version 10 and SPSS version 16. Antenatal/postnatal and control group and preconception and control group scores for each test session outcome measure were compared. The study received ethics approval.
Results: Data reveal a significant pregnancy group deficit in mean spatial recognition memory (SRM) % correct score compared to the control group during the second (70 vs 82% P=0.001) and third trimesters (73 vs 80% P=0.03) and at 3 months following birth (68 vs 80% P=0.0001). There was also a significant reduction in antenatal SRM score between first and subsequent testing occasions. The pregnant group also had significantly higher mean EPDS and GHQ12 scores in the first and second and first, second and third trimesters respectively. Control group scores were stable across all testing occasions and on all measures apart from intra/extra dimensional shift adjusted errors which indicated a learning effect. There were no group differences when NART, BMI and age were compared.
Conclusion: Data support the hypothesis that pregnancy adversely affects ability to perform certain cognitive tasks, specifically memory for previously seen spatial locations. Increased EDPS and GHQ12 scores indicate pregnant women have lower mood and greater risk of depression.