THE REAL
BABY BRAIN
Motherhood messes with your mind – but not in
the ways you might think, says Emma Young
S
HE was still a fairly new graduate student
at Tulane University in New Orleans,
Louisiana, when her mentor handed her
a paper. “As I skimmed it, I realised it was
about cognitive impairment associated with
pregnancy and motherhood,” she says. “I also
realised no one else had been given the paper.”
Katherine Tombeau Cost was several
months pregnant at the time, so her mentor
intended the paper to be a joke between
friends – but it got her thinking. It’s widely
assumed that pregnancy and motherhood
turns women into sieve-brained shadows of
their former selves: the condition variously
called “mummy brain” or “baby brain” is a
familiar staple of popular culture. But when
Tombeau Cost started digging through the
scientific literature, she found little evidence
to support it. Indeed, she found evidence to
the contrary – at least in rats, which become
mentally sharper after giving birth. “There
had to be another side of the story,” she says.
So she set out to find it.
The picture that is emerging tells a very
different story about “baby brain”. The
research also holds promise for understanding
postnatal depression, and even factors that
contribute to healthy brain ageing in all
women. Busting the myth, then, could
advance society in more ways than one.
It’s true that pregnant women and new
mothers often report cognitive problems.
In surveys, up to four-fifths of pregnant
women report that they have more trouble
remembering phone numbers or stringing a
complex sentence together than before they
got pregnant. Those results appeared to be
bolstered by a widely cited 1997 study
revealing that women’s brains shrink by up to
36 | NewScientist | 9 January 2016
7 per cent over the course of a pregnancy.
All this would have been news to Craig
Kinsley. It was watching his wife and newborn
daughter that started Kinsley, a neuroscientist
at the University of Richmond in Virginia
wondering about cognitive improvements
brought on by motherhood. “I watched her
with the baby, and she knew almost
instinctively what to do. And I watched her
doing everything she did before – working
and now also taking care of the baby,” he says.
“It got me thinking: from a rat standpoint,
what changes would benefit a mother rat?”
That was what led Kinsley to do the research
that later attracted Tombeau Cost’s interest.
In his years of studying the neurobiology
underlying social behaviours in rats, his
animals had never shown any evidence of
baby brain. Quite the opposite, actually.
Although rats in the final phase of their
pregnancy show a slight dip in spatial ability,
after their pups are born they surpass nonmothers at remembering the location of food
in complex mazes. Mother rats are also much
faster at catching prey. In one study in
Kinsley’s lab, the non-mothers took nearly
270 seconds on average to hunt down a cricket
hidden in an enclosure, whereas the mothers
took just over 50 seconds.
A new wave of research, by Kinsley’s
team and others, is now also showing that
mother rats are bolder. Placed in a stressful
situation, they show less fear and anxiety,
have lower levels of stress hormones in their
blood, and display less activity in brain regions
that regulate fear and anxiety, such as the
amygdala.
What underpins these dramatic changes?
Kinsley and his colleague Kelly Lambert at >
BRETT RYDER
9 January 2016 | NewScientist | 37
Baby-proof
A woman's brain shrinks slightly during pregnancy
but soon bounces back, better than ever
Final trimester
Brain loses 7% of its volume on average
relative to before pregnancy
Six months after birth
Brain regains its original volume, and areas involved in
cognitive and processing emotion have formed dense
new neural connections
Reasoning, judgement
and emotion regulation
Ventrolateral Dorsolateral
prefrontal prefrontal
cortex cortex
Emotion
recognition and
empathy
Insula
Superior
temporal
gyrus
Thalamus
Emotion
regulation
Hypothalamus
Amygdala
38 | NewScientist | 9 January 2016
Learning
Substantia
nigra
end of the story. Between about three weeks
and four months after birth, some regions
bulk up: including those that play a role in
reasoning and judgement, empathy and
regulating emotions (see diagram, below left).
In adults, such rapid changes in grey matter
normally occur only as a result of major events
like illness or brain injury. It just goes to show
that “pregnancy is not just some minor event”,
as Kinsley puts it. “These changes represent a
separate developmental period every bit as
important as sexual differentiation or
puberty.”
But do they lead to the same kinds of
emotional and cognitive improvements found
in rats? Laura Glynn at Chapman University in
Orange, California, has found that, as in rats,
women in the last trimester of pregnancy tend designed to replicate the rat work. For
example, to emulate the maze task, Tombeau
to be much less stressed. This is down to a
Cost put women into a virtual pool of water
dampening of the hypothalamic-pituitaryto find a hidden platform on which to rest.
adrenal axis, the system responsible for the
flight-or-fight response. These changes appear She painstakingly measured the distance the
women travelled, the time it took them to find
to last beyond pregnancy, although for
precisely how long remains unclear.
Intriguingly, human mothers also become “Women became bolder and
more aggressive than non-mothers when
more emotionally resilient
provoked (Psychological Science, vol 22,
after giving birth”
p 1288).They also become bolder and more
emotionally resilient. This all makes
the platform, and a host of other factors.
evolutionary sense, says Lambert, because a
Her results, not yet published, were
tough mother would better protect her
offspring, and a blunted stress response would consistent with all the earlier work on
humans: no matter how she did the
make her more resilient and able to cope with
experiment, she found neither impairments
the many demands of her baby. This benefits
nor improvements in the women’s spatial
her child in more ways than one, as severe
ability.
maternal stress during and after pregnancy
The reason, when she finally saw it,
has been shown to harm the baby’s physical
was blindingly simple: of course the skills
and mental health.
motherhood boosts in women won’t be the
same ones it boosts in rats. Female rats raise
Brain boost
pups alone, without help from the fathers or
However, the similarities with rats end there.
other rats. Boosts in spatial awareness and
Lab experiments generally have not found
memory help her find food and get back to
women’s cognitive performance to be either
her pups speedily. Humans evolved to live in
impaired or improved during pregnancy or
groups, so mothers don’t face the same
early motherhood, either in spatial reasoning
evolutionary pressures.
or memory. The few reliable results that do
So what brain changes would help a human
show a dip relate to verbal memory, in the
mother raise her infant? It’s early days, but
third trimester and in the few months after
experiments are yielding clues. Starting in late
giving birth, but it is as slight as it is
pregnancy, women get better at detecting fear,
temporary. This is probably a consequence
anger and disgust in computer-generated
of the major brain changes that takes place
faces, though their ability to detect surprise
during pregnancy, says Glynn.
and positive emotions such as happiness
So, intrigued by Kinsley’s rat research,
doesn’t change. This makes sense, says Glynn:
Tombeau Cost set out to discover whether
“If you’re trying to protect your infant, you
maternity might improve women’s spatial
want to be able to detect a threat.”
ability. She gave pregnant women,
Motherhood may also make women more
breastfeeding mothers and women who had
strategic, helping them take the demands of
never been pregnant a host of challenges
having a baby in their stride with little or no
DENIS BOURGES/TENDANCE FLOUE
Randolph-Macon College in Ashland, Virginia,
believe it is the tide of hormones unleashed
during pregnancy, including oestradiol, which
soars to levels hundreds of times higher than
normal. Then there’s oxytocin, which primes
the brain to transform rapidly in response to
sensory stimulus from the pups: areas
involved in memory and cognition undergo
major changes in rat mothers, forging more
connections between neurons.
Pregnancy and motherhood prompt a
number of changes in women’s brains,
according to recent MRI studies. Quite why the
brain shrinks during late pregnancy isn’t well
understood, but this shrinkage is now known
to be temporary. By about six months after a
woman gives birth, her brain will have
regained its original size. But that’s not the
Contrary to popular
opinion, it won’t
scramble your brain
JEAN-LUC BERTINI
impact on the way they cope with existing
pressures in their lives. As yet, there are no
studies probing this, but Lambert and her
colleague Massimo Bardi are designing new
experiments. They are intrigued by research
on owl monkeys, showing that mothers are
better than non-mothers at identifying big
stores of food and devising effective strategies
to get them. There’s a good chance that this
research will generalise to humans, not just
because we are primates too: unlike rat dads,
owl monkey fathers contribute equally to the
raising of the offspring.
Glynn is also leading work to fill in some of
these gaps. For example, she is giving a group
of pregnant women a battery of tasks designed
to investigate abilities such as strategic
planning and multitasking, and will follow
their performance for at least a year after birth.
Our lack of understanding of the full
impacts of motherhood on the brain is a sore
point for her. “In my opinion it’s almost a
crisis in women’s health,” she says. “How can
we not know the answers?”
That’s because the implications of baby
brain go far beyond a bit of fuzzy thinking.
Around a fifth of women experience
postnatal depression within three months of
giving birth. In the UK, suicide is one of the
leading causes of death in new mothers.
Abnormal levels of hormones associated
with pregnancy may be to blame. In proper
amounts, these are critical for fetal
development and other aspects of the
pregnancy. For example, corticotropinreleasing hormone – secreted by the
hypothalamus – rises dramatically during
pregnancy, which seems to play a role in
making the mother-to-be feel less stressed.
But an abnormal spike in its levels is
associated with postnatal depression, Glynn
has found. A better understanding of the
maternal brain and of what hormone levels
are beneficial could improve our strategies to
prevent the condition.
It could also augment our understanding
of the factors that contribute to healthy brain
ageing. Research on the impacts of pregnancy
on a woman’s health later in life is just
beginning, but Liisa Galea at the University of
British Columbia in Vancouver, Canada, has
found evidence that having children alters
women’s hormone levels for years. “It
shouldn’t be surprising that researchers are
seeing long-lasting effects of motherhood,”
she says.
For Kinsley’s rats, the cognitive
improvements lasted well into old age.
“We’ve looked at animals up to 2 years of age,
which for rats is equivalent to a woman in her
mid-80s,” he says. “They still learn more
quickly, they’re faster on their feet, and their
brains are healthier than in a virgin animal
at that age.” Neuroscience backs up these
behavioural findings: the brains of older rat
mums look healthier than those of nonmothers, containing fewer deposits of
amyloid precursor protein, which in humans
is linked to Alzheimer’s.
However, the evidence from work in humans
is contradictory. One study finds a correlation
between the number of children a woman has
and her Alzheimer’s risk. Other work, by Glynn
and collaborator Molly Fox, suggests that
breastfeeding may protect against
Alzheimer’s – as could more pregnancies.
Future studies can unpick these
contradictions, says Fox, if they look
specifically at the role of maternity hormones
on Alzheimer’s. There may be more than just
hormones involved – a baby’s cells could be
invading the mother’s brain to grow new
neurons (see “The others inside you”, page 26).
Either way, a better understanding of
pregnancy’s effects on women throughout
their lives could unlock new strategies to
reduce the risk of the disease.
A better grasp of exactly what changes
occur with motherhood could even improve
our understanding of human evolution, says
Glynn. “A reptile that lays eggs and leaves
them – you don’t see a lot of complexity in
that brain,” she says. Evolving new ways of
raising offspring required more neural
energy and behavioural changes. Did this
new repertoire of behaviours increase the
complexity of the animals, or vice versa?
“This is profoundly important stuff,” she says.
Myth-busting
Busting the myth of baby brain once and for
all might also have practical consequences.
Plenty of policies are in place to prevent
discrimination in hiring practices and protect
a woman’s right to return to work after having
a baby. However, they don’t address
underlying prejudices.
“The idea of ‘baby brain’ seems to be
prevalent,” says Tombeau Cost. For example,
she has found that women who have never
been pregnant rate their own spatial ability
more highly than pregnant women or those
who have had children. How much of this is a
consequence of cultural priming and
stereotypes that influence women’s
perceptions of their own brainpower? And
what about the chronic sleep deprivation
that accompanies the earliest stages of
parenthood? This has been shown to have
similar effects on brain functioning as
drinking alcohol.
Tombeau Cost hopes the new research will
assure women – and their employers – that
underneath it all, their brains are just fine.
Maybe better than fine. The research into
the cognitive benefits of motherhood could
make women of childbearing age an attractive
hiring prospect for employers, rather than a
potential liability. For example, the improved
threat detection would offer particular
advantages in some types of jobs, says Kinsley:
“consider fighter pilots and astronauts.”
Lambert is uniformly positive. “Being able
to be more efficient in your decision-making,
being emotionally resilient, maybe being able
to engage in different strategies to solve a
problem: that sounds like a wonderful
executive or manager to me,” she says. ■
Emma Young is a writer based in Sheffield, UK
9 January 2016 | NewScientist | 39