The popular belief that pregnancy addles women's brains is a myth, a comprehensive study suggests.

Mothers claim to have suffered 'baby brain' or 'preg head', characterised by lapses in memory or logical thinking.

But researchers who tracked 2,500 women over ten years found no difference between their brainpower before and during their pregnancies.

In fact, the scientists believe, pregnancy and motherhood could actually improve women's mental abilities - and the improvement may be permanent.

Previous studies have claimed that pregnant women's brains decline in size and that they consistently perform worse than other women on tests for memory and verbal skills.

They have suggested that the difference could be as great as comparing the mental ability of someone aged 20 with someone aged 60.

But Professor Helen Christensen, of the Australian National University in Canberra, said her study is superior to previous research because it compares the same women before and during pregnancy.

'Women often report problems with memory and reasoning after they become pregnant,' she said. 'But the latest findings from our decade-long study, the most in-depth to look at this issue, has proven they do not.'

The researchers studied 2,500 women aged from 20 to 24, first in 1999 and then again in 2004 and 2008.

'We found that women who were pregnant during the second or third batch of interviews performed the same on tests of logic and memory as they did before, and there was no difference between the pregnant women and the controls,' she said.

'It really leaves the question open as to why women think they have poor memories, when the best evidence we have is that they don't.

'Perhaps women notice minor lapses in mental ability and then attribute it to being pregnant because that is the most significant thing in their mind at the time.

'Or sleep deprivation could mask the positive cognitive effects.'

一项大规模研究表明，“怀孕会影响女性智力”的普遍观点其实并不正确。

很多妈妈称她们在怀孕期间有“婴儿脑”或“怀孕脑”现象，主要表现为健忘和反应迟钝等。

但研究人员对2500名女性进行的一项为期十年的跟踪调查发现，女性的智力水平在怀孕前和怀孕期间没什么差别。

研究人员认为，女性怀孕当妈妈以后的智力水平反而比以往有所提高——而且这种提高可能是长期的。

此前的研究认为，女性怀孕后大脑会变小，相应地，她们在记忆力和语言能力方面的测试不如其他女性。

这一差别与20岁和60岁人群之间的智力差异差不多。

但位于堪培拉的澳洲国立大学的海伦?克里斯坦森教授称，她的研究超越了此前的研究，因为她的研究对比的是同一女性在怀孕前和怀孕期间的智力水平。

她说：“女性在怀孕后常称自己的记忆力和逻辑思考能力出现退化。但我们的这项长达10年的最新研究证明事实并非如此，这是目前有关这一课题最深入的一项研究。”

研究人员对2500名年龄在20岁至24岁之间的女性进行了研究，首批研究于1999年进行，另外两批分别于2004年和2008年进行。

海伦说：“我们发现在第二或第三批访问期间怀孕的女性在逻辑和记忆力测试中的表现与怀孕前差不多，而且怀孕女性与控制小组的女性在测试中的表现也没什么差别。”

“这就留下了一个疑问，为什么女性觉得自己怀孕后记忆力变差了，而我们掌握的最有力的证据则表明事实并非如此？”

“可能女性注意到自己的智力水平稍有下降，就将其归于怀孕所致，因为那段时期她们的注意力都集中在‘怀孕’这件事上了。”

“或者睡眠不足可能也会掩盖积极的认知效果。”