The impact of healthy pregnancy on maternal cognitive impairment in Sprague Dawley rats

Introduction/Background: There is clinical evidence of impaired attention, learning, and memory in pregnant women during pregnancy and in the postpartum period, suggesting an association between pregnancy and maternal cognitive dysfunction. Yet, the effects of pregnancy on memory impairment are unclear. We hypothesized that pregnancy would induce maternal cognitive dysfunction that would persist postpartum in a rat model of healthy pregnancy. Methods: To observe recollective memory, the novel object recognition test was performed using Sprague Dawley female rats with different reproductive histories [non-pregnant virgin, late gestation (gestational day 20, term = 22-23 days), postpartum (28 days after birth), and parous non-pregnant (60 days after birth); n = 7-8/group]. Each rat was placed into an empty arena without objects, to allow for adjustments to the open arena. Thirty-minutes after habituation, each rat was given a period of five minutes to explore the arena with two objects of identical size, color, and texture. Upon completion, one hour was given before the animal was placed back in the arena. To test short term recollective memory, each rat was given three minutes to explore two items: one familiar item and a novel item of different size, color, and texture. The latency to which the animal made the initial contact for each object was recorded, and the number of contacts made with the novel object were tallied and compared with overall contacts to each object. Results: Pregnant rats had increased latency to initial contact of the novel object (p < 0.05) compared to virgin females, postpartum dams, and parous non-pregnant dams. Additionally, parous, non-pregnant dams displayed significantly greater contacts with the novel object (p < 0.05) compared to pregnant rats and postpartum dams. Conclusion: Overall, healthy pregnancy results in decreased short term memory recognition that can be repaired over time. Future directions include evaluating the impact of healthy pregnancy on long term memory recognition, examining underlying mechanisms contributing to cerebral impairments during pregnancy, and determining the effects of pregnancy complications on memory impairment.