Tracy Packiam Alloway, PhD

So this week I have burnt the pasta (twice!), put the milk away in the cupboard with the glasses, and locked the car and house keys in the car. If you asked me in my six-month of pregnancy whether pregnancy brain is a myth, I would say NO!

Some pregnancy women blame such actions as the result of the lack of sleep. However, it seems that I can’t use sleep deprivation as an excuse for my forgetfulness. Studies have found that the lack of sleep is not actually linked to memory loss and forgetfulness in pregnant women.

Thankfully, there is a reason for my new (and unwanted!) absent-minded brain. Scientific studies show that during pregnancy, a woman’s brain changes*. For starters, the hippocampus, which is linked to spatial memory and long-term knowledge, actually shrinks during pregnancy. This means that a pregnant woman’s sense of direction is not always as reliable as it used to be.

Why does the pregnancy brain shrink? The brain shrinkage is the result of hormone changes during pregnancy, especially in the final trimester. Some hormone levels, such as progesterone and estrogen, rise and fall during pregnancy. We need a perfect balance of these hormone levels to use working memory-our ability to incorporate new information with long-term knowledge stores. When estrogen are very high, such as during the last trimester of pregnancy, working memory is not as efficient. This makes simple tasks like remembering that the milk goes in the fridge (and not the cupboard) or juggling multiple tasks at work a little more difficult than usual.

Happily, brain size goes back to normal after the baby is born. Pregnant women can be confident of performing to their usual cognitive capabilities, but be aware that the pregnancy brain means that they may be more affected than usual when taking on additional responsibilities.

From TRAINING YOUR BRAIN for Dummies (due Dec 2010)

* Galea et al. (2000). Hormones and Behavior.