Pregnant women do not display impaired memory formation across one night of sleep.

Forgetfulness is a common complaint of pregnant women, who also often report impaired nocturnal sleep. Considering sleep's well-known beneficial role in consolidating newly encoded memory content, we hypothesized that pregnant women would display detrimental changes in objective sleep measures and associated memory deficits. We compared the consolidation of declarative as well as procedural memory across sleep in 21 healthy, third-trimester pregnant women versus 20 matched non-pregnant controls. Subjects encoded and were tested on visuospatial and procedural memory tasks before and after, respectively, a night of sleep spent at home. The emergence of gist-based memories was tested with the Deese-Roediger-McDermott (DRM) paradigm. Sleep was polysomnographically recorded and subjective sleep quality was assessed with questionnaires. Although pregnant in comparison to non-pregnant women reported markedly impaired subjective sleep quality and efficiency, quantitative changes were limited to increases in wakefulness after sleep onset and reductions in rapid eye movement (REM) sleep. Retention of newly learned memory contents, which is believed to reflect sleep-associated memory consolidation, was comparable between groups, as was the formation of gist-based memories. The findings indicate that subjective deteriorations in sleep quality experienced by pregnant women are not necessarily linked to objective impairments. They raise the possibility that sufficient slow wave sleep towards the end of pregnancy allows for normal sleep-related memory consolidation. Although these results were obtained in a small number of pregnant women in very good health and should be corroborated in larger samples, they challenge the assumption of poor sleep and impaired memory as hallmarks of the "pregnancy brain".