If you have never used the term “baby brain” are you even a parent? By my third, I could barely remember what I went upstairs for, now by number four I survive on lists and reminders and a lot of acceptance that I forget things a lot!

For those of you who have never heard the term 'baby brain' it is the period of your life when you seem to become forgetful and absent-minded for no apparent reason. Research shows about four out of five women report experiencing cognitive changes during pregnancy.

Symptoms include forgetfulness, poor concentration and feeling they are "not as sharp" as normal.

For years mums have talked about this while many experts have said it is not a condition and is merely the body's response to the exhaustion associated with a succession of sleepless nights.

But a recent Australian study has shown that “baby brain” is a genuine, measurable phenomenon. Researchers at Deakin University undertook 20 studies involving more than 1,200 women.

They found overall cognitive functioning was poorer in pregnant women than in non-pregnant women.

"General cognitive functioning, memory, and executive functioning were significantly reduced during the third trimester of pregnancy, but not during the first two trimesters," the authors wrote.

Executive function covers attention to detail, planning and problem-solving.

The study, published in the Medical Journal of Australia, found changes to cognitive functioning and memory occurred early in pregnancy, but did not become apparent until the third trimester.

"The declines start to happen between the first and the second trimester, and then look like they stabilise … but are most obvious in the third trimester," senior author Associate Professor Linda Byrne said.

Lapses were more likely be minor such as forgetting or failing to book medical appointments, rather than impaired performance at work, or an inability to navigate complex tasks.

Professor Byrne said the results were consistent with recent findings of long-term reductions in brain grey matter volume during pregnancy.

"It looks like the reason pregnant women have grey matter reduction is because they're probably recruiting those areas to more important areas associated with the business of child-rearing — so things like bonding, and social cognition," she said.

Researchers say the next step is understanding how these changes to cognitive function affect the lives of pregnant women.

"The impact of these effects on the quality of life and everyday functioning of pregnant women requires further investigation," Associate Professor Byrne said.

Researchers said exactly why memory and executive function is impacted by pregnancy remains unclear.

And it is not yet known whether brain function returns to normal levels after giving birth. Here’s hoping!

Readers, have you experienced baby brain? Did it get worse with each pregnancy? Let us know in the comments!