Is "pregnancy brain" a myth or a real brain change?

Is “pregnancy brain” a real thing? — Is “pregnancy brain” a myth or a real brain change? (Photo: iStock)

Pregnancy brain, often called “mum brain” or “momnesia”, refers to the common experience of mild cognitive changes such as forgetfulness, difficulty concentrating and mental fog during and shortly after pregnancy. These changes are often attributed to significant hormonal shifts (particularly oestrogen), sleep disruption, stress, and even measurable structural brain changes.

Science now shows that “pregnancy brain” is very real and it’s not about losing brain power. Instead, it’s about the brain reshaping itself for motherhood. A major study led by neuroscientist Dr Elseline Hoekzema, published in Nature Neuroscience, found that pregnancy causes subtle reductions in grey matter in areas of the brain linked to social awareness and emotional understanding. Rather than being a negative change, researchers believe this fine-tuning helps new mothers become more attuned to their baby’s needs.

What’s even more striking is how consistent these changes are. The same brain patterns have been observed in women who conceived through IVF, suggesting this isn’t driven by expectation or lifestyle, but by biology itself. And while overall intelligence remains unaffected, studies have noticed small, temporary changes in memory, especially working memory. In fact, a 2016 brain-imaging study found these changes were so distinct that scientists could tell whether a woman had been pregnant simply by looking at her brain scans.

Hormonal surges play a significant role in driving these effects. Levels of progesterone and oestrogen can increase by 15 to 40 times during pregnancy, influencing neurons and neurotransmitters involved in focus and memory. As oxytocin rises during labour, it further reshapes brain circuits associated with nurturing and attachment.

Progesterone is often linked to feelings of “brain fog”, while fluctuations in oestrogen may affect concentration. These hormonal changes prioritise fetal development, effectively redirecting the brain’s resources. When combined with disrupted sleep and increased fatigue, memory and focus can be universally affected.

In addition, stress related to major life changes and constant multitasking may increase mental overload. Nutritional demands, particularly the diversion of energy to support fetal growth, have also been suggested as contributors to theories around temporary brain shrinkage. Other factors, such as dehydration and anaemia, may worsen symptoms, while expectations and self-reporting can amplify the perception of forgetfulness.

Although these effects are generally mild and temporary, a little care can make a noticeable difference. Many people manage pregnancy brain by using apps, lists and reminders to stay organised. Prioritising sleep, hydration and an omega-3-rich diet, delegating tasks, and practising mindfulness can significantly reduce stress. Regular exercise is also an effective “therapy”, as it boosts blood flow to the brain and helps counter cognitive fog.

“I don’t think they are just forgetful; I think it depends on their mental health state. They may simply become absorbed in what is troubling their mind at the moment and therefore appear to forget others. Alternatively, they may push unpleasant stimuli into the subconscious, which can seem like forgetting,” explains Dr Linah Ochieng', a psychologist.

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While these strategies may help manage symptoms during this temporary nine-month phase, occasional forgetfulness over small things is generally nothing to worry about.