Yes, Pregnancy Means Your Brain 'Shrinks'. But It's Not All Bad

It basically has a clear out.
Dusan Stankovic via Getty Images

“Un-fun fact: incubating a tiny human can indeed cause a pregnant woman’s brain to shrink and this volume loss can last up to two years,” said Dr Karan Raj, who is known for his health explainers and myth-debunking, in his latest TikTok video.

“Specifically, there’s evidence that it’s a brain’s grey matter which shrinks – that’s the tissue containing the cell bodies and synapses of nerve cells.”

Alas, he is correct. A study of women during and after pregnancy revealed the brain decreases in size when growing a baby in the womb and then increases again after delivery.

For those with preeclampsia, brain size was “significantly smaller” than in healthy participants, both before and after delivery.

It’s thought these changes can last anywhere between a matter of months up to two years after giving birth. But never fear. There may be a perfectly normal explanation for this – and it’s not necessarily a bad thing.

“While losing grey matter sounds like it might be detrimental and will lead to a loss of function, actually the effect might be the total opposite. Volume loss could lead to a fine tuning or streamlining of brain connections,” said Dr Raj.

He likened the effect to what happens in teenagers’ brains as they develop – where hormones trigger the widespread pruning of synapses (aka the connection between nerve cells) – “this makes for more efficient streamlined brain circuits”.

So what does all this actually mean?

Well, it’s thought the grey matter shrinkage in pregnant women happens in brain areas involved in processing and responding to social signals.

The theory is that the brains of new mums become “more efficiently wired in areas that allow them to respond to their infant’s needs or detect threatening people in their environment,” explained Dr Raj, before adding that “what seems scary might actually be an adaptive advantage to be a better parent”.

It’s a bit like your brain is rearranging the furniture – having a clear out, if you like – to improve its chances of keeping your little one alive.

Studies have also found there’s no evidence memory deteriorates during pregnancy – so that’s a bonus. Although many mums still do anecdotally report forgetfulness and brain fog after having kids.

The brain changes that occur happen in women regardless of how they conceived – whether through IVF or naturally.

When similar studies were conducted on fathers’ grey matter, there were no changes reported.

So next time you wonder if you’re firing on all cylinders during pregnancy, remember your brain is actually working wonders behind the scenes.

As neuroscientist and therapist Jodi Pawluski, of the University of Rennes in France, and her colleagues said in a comment piece for JAMA Neurology: it’s time to start giving the maternal brain “the credit it deserves”.

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