'Baby brain' is all in the mind, say scientists.
The phenomenon of mums-to-be becoming forgetful and scatter-brained doesn't actually exist – in fact, expectant mothers are just as switched on as other women.
And other key skills, including attention span and spatial awareness, are equally unaffected by pregnancy, according to the research.
Up to 80 per cent of pregnant women say they suffer memory lapses, but scientists believe this is because they've convinced themselves they're going doolally to conform with the 'stereotype that your brain is going to turn to mush' when pregnant.
Scientists from Brigham Young University in Salt Lake City put 21 mothers-to-be through a battery of mental tests a few weeks before their baby was due and again a couple of months after the birth.
Another 21 women who weren't pregnant and had never had any children also completed the three-hour set of tests.
There were no differences between the two groups in memory, thinking, attention span, organisational or spatial skills.
Whether the tests were taken during pregnancy or when looking after a young baby, the women did just as well as those who had never been pregnant.
However, when asked how they had performed, the pregnant women and new mothers thought they had done worse. They also said they had a lower quality of life and were less satisfied with their lot.
Psychology professor Michael Larson, lead author of the study, said: "I was surprised at how strong the feeling was that they weren't performing well.
"This feeling of, 'I really am doing badly right now' exists despite the objective evidence that they aren't."
Writing in the Journal of Clinical and Experimental Neuropsychology, Professor Larson said that the expectation of baby brain may be so strong that a pregnant woman is extra-alert to memory lapses.
So, although they happen no more than usual, she may notice them more and therefore think they do.
Prof Larson said that women should realise that what they are feeling is all in their minds and if they believe their mind is working at full capacity, then it will.
He said that he hoped pregnant women would hear about his research findings and these would 'improve their quality of life, improve how they are functioning – they might start believing in themselves'.
What do you think about this? A study of 42 women doesn't sound enormously robust?