Many women believe that they become more forgetful during pregnancy: a new study by Australian researchers suggests that they are right - and that their memory can be significantly impaired for at least a year after giving birth.

Only some aspects of memory are affected, especially those of an unfamiliar or demanding kind, and the level of impairment is not large.

"But the memory deficits many women experience during and after pregnancy are pretty much like the modest deficits you'd find when comparing healthy 20-year-olds with healthy 60-year-olds," says Dr Julie Henry of the School of Psychology at UNSW, who conducted the study with Associate Professor Peter Rendell, of the Australian Catholic University.

In the first investigation of its kind, the researchers conducted a meta-analysis of the results of 14 different research studies around the world since 1990 where the memory performances of more than 1,000 pregnant women, mothers and healthy non-pregnant females had been compared.

They found that pregnant women are significantly impaired on some, but not all, measures of memory and that they experience most difficulty with tasks that rely on "executive cognitive control" - that is, memory tasks where novelty or significant effort is involved.

"Regular, well-practised memory tasks - such as remembering phone numbers of friends and family members - are unlikely to be affected," says Associate Professor Rendell. "It's a different story, though, when you have to remember new phone numbers, people's names or hold in mind several different pieces of information, such as when multi-tasking ."

Until recently, much of the evidence for pregnancy-related memory deficits was either anecdotal or based on subjective reports. The new study, published recently in the Journal of Clinical and Experimental Neuropsychology, is the first to assemble and analyse the data from a wide range of scientific studies into the phenomenon.
The results indicate that the impairment - dubbed "baby brain" - is still evident a year after childbirth. Since none of the studies has extended beyond that time, it is not known how long the deficit continues.

Nor do scientists know why a woman's memory should be impaired at such an important time, although several theories have been put forward.

"Although we have no experimental evidence for it, our suspicion is that lifestyle factors are relevant," Dr Henry says. "In pregnancy your normal routines are disrupted and you can suffer sleep deprivation after the birth: we know from other research that either of those things can affect cognitive performance."

Courtesy of UNSW Faculty of Science (Media liaison: Bob Beale - mobile, 0411 705 435)