We're referring to the increased forgetfulness, lack of attention and mental 'fog' that are noted by the majority of women throughout their pregnancy.
Researchers from Deakin University analysed the results of 20 existing studies about the relationships between pregnancy and brain changes, and were able to use this information to take it one step further in their own study.
Armed with the knowledge, Sasha Davies, one of the study's authors wrote on The Conversation that they were able to produce the first study of its kind, delving into how pregnancy affects cognitive areas other than memory according to what stage you are in your pregnancy.
The study involved 1,230 women, specifically 709 pregnant women and 521 non-pregnant women.
The researchers used various tasks to measure the women's cognitive abilities, with the view to compare them afterwards.
Publishing their findings in the Medical Journal of Australia, the results showed that pregnant women did actually perform much worse than non-pregnant women in certain tests.
This was particularly true for the tasks measuring memory and executive functioning - which includes attention, inhibition, decision-making and planning.
The research has also suggested that 'baby brain' does affect women differently depending on which stage they're at in their pregnancy.
Cognitive behaviour appeared to decline from the first trimester, but was more stable through the middle and end of pregnancy.
Despite these findings, there's still no evidence to suggest what actually causes 'baby brain'.
Sasha said, that we've still got a very 'long way to go' before causes or even preventions can be determined.
However, there's no need to be alarmed because while the research does prove that the brain's function does decline, the pregnant women were still broadly performing within what they'd consider a 'normal' range.