Pregnancy brain is not an excuse but biology
Forgotten keys in the fridge, a colleague's name that simply won't come to mind, or a shopping list written an hour ago that's nowhere to be found. Every pregnant woman knows these moments – and if she doesn't, her surroundings certainly do. The phenomenon known as pregnancy brain – referred to in English as pregnancy brain or momnesia – is the subject of both mockery and genuine frustration for millions of women around the world. But the question remains: is it a real neurological phenomenon backed by science, or merely a convenient excuse for moments of inattention?
The answer is surprisingly clear-cut – and in recent years, science has come down firmly on the side of pregnant women.
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What Actually Happens in the Brain During Pregnancy
From a biological standpoint, pregnancy is one of the most radical processes the human body can undergo. Hormones change, blood volume shifts, organ function alters, and sleep cycles are disrupted. What has long been underestimated, however, are the changes occurring directly in the brain. Research published in 2017 in the prestigious scientific journal Nature Neuroscience brought a groundbreaking discovery: pregnancy causes measurable and long-lasting structural changes in the brain's grey matter. And not merely temporarily – these changes persist for at least two years after childbirth.
Spanish scientists led by Elseline Hoekzema tracked the brains of women before pregnancy, after childbirth, and again two years later. The results showed that the volume of grey matter in certain brain regions decreases during pregnancy – but crucially, this does not mean the brain is "deteriorating." Quite the opposite. The researchers interpret this reduction as specialisation and a streamlining of neural connections, similar to what occurs during puberty. The brain sheds unnecessary synaptic connections so that the remaining ones function more efficiently and with greater purpose. This process is known as synaptic pruning.
The areas that change most significantly are associated with social cognition, empathy, and the ability to read other people's emotions. In other words, the pregnant woman's brain is restructuring itself to be better prepared for motherhood – for recognising a newborn's needs, building emotional bonds, and responding swiftly to social cues. What outwardly appears as forgetfulness or absent-mindedness may in fact be a side effect of a profound and purposeful reorganisation of the brain.
Hormones also contribute to these changes. Levels of oestrogen and progesterone rise dramatically during pregnancy – oestrogen, for instance, reaches levels many times higher than outside of pregnancy. Both hormones directly influence neurotransmitters, the chemical messengers in the brain that regulate mood, memory, and concentration. Progesterone has a sedative effect on the central nervous system, which may explain the feelings of mental fog, fatigue, and slowed reactions, particularly in the first trimester.
Cortisol, the stress hormone whose levels also rise during pregnancy, plays its own role. Chronically elevated cortisol is a well-documented enemy of memory – it negatively affects the hippocampus, the part of the brain crucial for forming new memories. The combination of all these hormonal changes creates an environment in which it is simply harder for the brain to function as it once did.
To this we can add one more factor that is often overlooked in discussions of pregnancy brain: sleep. Pregnant women – especially those in the later stages of pregnancy – sleep significantly worse than before conception. Frequent trips to the bathroom, back pain, foetal movement, and general physical discomfort all disrupt sleep. And sleep deprivation alone causes precisely the symptoms attributed to pregnancy brain: forgetfulness, difficulty concentrating, and slower information processing.
Science Versus Everyday Experience
Although research clearly confirms structural and functional changes in the brain, the situation in everyday life is somewhat more complex. Not all studies agree on the practical magnitude of these changes. Some research shows that differences in memory performance between pregnant and non-pregnant women, while statistically measurable, are relatively small in real life. Other studies, however, document more pronounced difficulties with working memory – that is, the ability to hold multiple pieces of information in mind simultaneously and work with them.
An Australian research team from Deakin University conducted a meta-analysis of 20 studies in 2018, encompassing more than 700 pregnant women and a comparable number of non-pregnant control subjects. The conclusions were clear: pregnant women performed worse on tests of memory, attention, and information processing – particularly in the third trimester. At the same time, the researchers emphasised that these differences may not be dramatically apparent in everyday life, as the brain has a remarkable capacity to compensate for partial deficits through alternative strategies.
It is also interesting to consider how women themselves perceive their difficulties. Research shows that the subjective sense of memory impairment among pregnant women is considerably stronger than would be expected based on objectively measured results. This may have several explanations. For one, pregnant women pay closer attention to their lapses and attach greater significance to them, being aware of their condition. Psychological factors may also play a role – anxiety about motherhood, an overload of information to process, and the simple fact that the mind is occupied with far more important matters than where the car keys are.
Consider Lucie, a thirty-two-year-old accountant from Brno, who in the third trimester of her first pregnancy began making errors in routine calculations she would never previously have thought to double-check. "I knew I could do it, but the numbers just didn't come as quickly as before," she recalls. "My colleagues told me not to worry, that it was normal – and they were right. Two months after giving birth, I was back to my usual self." Lucie's experience is typical: the symptoms are real, but they are usually temporary.
Why This Matters More Than It Seems
Dismissing pregnancy brain as an excuse, or as something women merely "imagine," has real consequences. Women who encounter incomprehension or mockery may begin to doubt their own abilities, feel less competent at work, and suffer needless anxiety. Yet the truth is that understanding the biological basis of these changes can significantly reduce stress and help women cope with them more effectively.
As neuroscientist and author of The Female Brain, Louann Brizendine, put it: "The pregnant woman's brain undergoes the greatest neurobiological transformation of her life – and yet most women know very little about it."
Awareness is, in this case, a genuinely powerful tool. If a woman knows that her forgetfulness has a specific neurological basis, she can approach it with perspective rather than panic. She can create systems to help herself – writing lists, setting phone reminders, sharing tasks with her partner. This is not an admission of weakness, but a pragmatic use of available tools during a period when the brain is undergoing profound restructuring.
It is also worth noting that the discussion around pregnancy brain touches on a broader issue: how society perceives and evaluates women's cognitive performance. Women have historically been more readily labelled as "emotional" or "unfocused," and pregnancy brain thus easily becomes yet another target for stereotypes. The scientific perspective dismantles these stereotypes – or at least, it should. The changes occurring in the brain are not a sign of weakness or incompetence. They are a manifestation of an extraordinarily complex biological process that has no parallel in human life.
It is also natural to ask what happens after childbirth. The structural changes in the brain, as the Spanish research demonstrated, persist – but their functional impact gradually shifts. New mothers face further challenges – chronic sleep deprivation, postpartum hormonal fluctuations, and an enormous emotional burden – yet the brain is simultaneously learning new skills and building new patterns. Some scientists even suggest that motherhood enriches and strengthens the brain in certain respects, particularly in the areas of empathy, multitasking, and rapid decision-making.
Pregnancy brain is therefore not the end of the story. It is more of a transitional chapter – demanding, sometimes frustrating, but also a fascinating demonstration of just how plastic and adaptable the human brain truly is. Science not only validates this experience, but lends it a depth and meaning that simply cannot be found in the dismissive label of "excuse."
