Pregnancy Doesn’t Actually Make Women Dumber
“Oh my gosh, I think my brain is permanently shrunk after having three kids,” CBS Early Show host Hannah Storm once said. In a diary for New Statesman, Sarah Montague, who co-hosts the BBC’s flagship Today news program, said: “My biggest worry has been what you might call ‘preg-head.’”
Storm
and Montague believe they were suffering from a kind of mental
impairment brought on by the biological changes associated with
pregnancy — an idea that’s been called preghead, pregnesia, momnesia and
baby-brain. Anecdotal evidence for the condition is everywhere and
frequently shared by writers and broadcasters. The idea has even been
endorsed by respected health authorities in the UK. An NHS
pamphlet published in 2005 on “50 things would-be fathers should know,”
put it this way: “Pregnant women are a bit vague … it’s their hormones.”
Surveys
suggest that belief in pregnesia is widespread among the public. In
2008, Ros Crawley at the University of Sunderland quizzed dozens of
pregnant and non-pregnant women and their partners, and found that they
all agreed that pregnancy is typically associated with cognitive decline.
Given
these views, perhaps it’s no wonder that researchers have uncovered
disconcerting evidence about the prejudice shown toward pregnant women,
especially in work contexts. Although such prejudice is driven by
multiple factors, widespread belief in baby-brain likely plays an
important part. Consider a study published in 1990, in which Sarah Corse
at the University of Pennsylvania invited male and female MBA
students to interact with a female manager they’d never met before, and
then rate her afterward. In fact, the “manager” was a research
assistant acting the part, and the key finding was that students given
the additional information that the woman was pregnant reported finding
their interaction with her less satisfying than students not fed this lie.
The
myth of the baby-brain hasn’t come out of thin air. Countless surveys
of pregnant women, using questionnaires and diary reports, have found
that many of them — usually about two-thirds — — feel that being
pregnant has affected their mental faculties, especially their memories.
Of course, that doesn’t mean that it has. Neither does it prove that
the cause is some biological consequence of the state of pregnancy as
opposed to lifestyle factors, like fatigue and stress.
The most dramatic claim about the biological effect of pregnancy on the brain is that it causes shrinkage (as mentioned by the CBS
host Hannah Storm). Given how drastic this sounds, you’d think it would
be backed up by plenty of evidence. In fact, the idea is based almost
entirely on a small study published in 2002 by researchers at Imperial
College School of Medicine in London. Angela Oatridge and her colleagues
scanned the brains of nine healthy pregnant women and five pregnant
women with preeclampsia (a condition associated with high blood
pressure), finding evidence of brain shrinkage of between 2 to 6.6
percent volume during pregnancy that was reversed six months after
giving birth. But without replication and a larger sample, it’s
difficult to take this single study too seriously.
Returning
to the issue of cognitive impairment, whereas subjective reports of
this from pregnant women are widespread, objective laboratory studies
are far less consistent. For many years, for every study that turned up
an apparent impairment in memory, another was published that drew a
blank. Some experts believed this was a sign that the effect is
unreliable and small; others said it was simply due to different labs
using different methods.
An
attempt to weigh all the evidence and get to the truth was published in
2007 by Julie Henrey of the University of New South Wales in Sydney and
Peter Rendell at the Australian Catholic University in Melbourne. They
conducted a meta-analysis that gathered all the evidence from 14 studies
published over 17 years. Their conclusion? There is a real effect of
pregnancy on women’s cognition, but it’s a “relatively subtle” one,
“relatively small in magnitude,” and it manifests most noticeably during
tasks that require executive functioning — that is, juggling lots of
information at once.
Unfortunately,
Henry and Rendell’s abstract (the summary) of their paper was worded in
a way that proved ripe for misinterpretation. They wrote, “The results
indicate that pregnant women are significantly impaired on some, but not
all, measures of memory.” By “significant” they meant statistically
significant: that is, unlikely to be due to chance. But journalists
worldwide misunderstood the research summary and the public message
became sensationalized: “many [pregnant] women … suffer considerable memory loss” (The Observer; emphasis added) and “pregnant women were considerably impaired (Hindustan Times; emphasis added).” These are just two examples of many.
Since
that meta-analysis, the literature has taken a number of further twists
and turns. An Australian study published in 2010 was superior to many
of its predecessors in following a large group of women over time and
testing their cognitive abilities, including working memory and
processing speed, prior to pregnancy, during, and after. And a handful
of other studies found associations between memory and pregnancy. But
then again, Helen Christensen and her colleagues found no evidence of
pregnancy being associated with cognitive decline.
Still,
taken altogether, it looks as though pregnancy really is associated
with cognitive changes in some women, including memory problems. The
inconsistent results could be a consequence of different methods used
and how relevant the tests are to real life. But this prompts an obvious
question — if baby-brain is a genuine phenomenon, why should female
humans have evolved to be mentally impaired just when you’d think they’d
need to be at their most alert?
Because
the cognitive problems associated with human pregnancy are all the more
mysterious in light of research with rats and other mammals that
suggests pregnant females undergo cognitive enhancements, not
impairments, that stay with them into motherhood. A pioneer in this
field is Craig Kinsley at the University in Richmond. He told me in
2010: “Our [maternal] rats get better at virtually everything they need
to, to successfully care for their expensive genetic and metabolic
investments. Foraging, predation, spatial memory all improve; stress and
anxiety responsiveness decreases.”
When
I asked Kinsley why the human literature was full of findings about
cognitive impairments while the animal research points to improvements,
he said the disparity may have to do with the kinds of tasks and
behaviors that were being studied in humans. “Much of the data from
human mothers has been derived from asking females to demonstrate
cognitive enhancements to skills, behaviors, occupations that are
largely irrelevant to the care and protection of young,” he said.
Another suggestion is that the baby-brain in humans is a side effect of
the dramatic changes underway in mothers’ brains that are gearing them
up for the demands that lie ahead. Framed this way, it’s the price
that’s paid for what is ultimately a maternal neuro-upgrade.
Recently,
a spate of human studies has been published that may be hinting at
these maternal advantages. For instance, James Swain’s lab at the
University of Michigan has shown how several areas in the brains of new
mothers are especially responsive to the sound of their own baby crying,
compared with the sound of other babies’ cries. Regarding physical
brain changes, a team led by Pilyoung Kim at Cornell University and Yale
University School of Medicine scanned the brains of 19 new mothers in
the weeks immediately after giving birth, and then again several months
later. The later scan showed increased volume in a raft of brain areas
that are likely to be involved in mothering activities — the prefrontal
cortex, parietal lobes, hypothalamus, substantia nigra, and amygdala.
And
in 2009 and 2012, labs at the University of Bristol and Stellenbosch
University, respectively, reported evidence that pregnant women have a
superior ability to determine whether a face is angry or fearful, and
they show heightened attention to fearful faces. The Stellenbosch team
wrote: “Heightened sensitivity to danger cues during pregnancy is
consistent with a perspective that emphasizes the importance of parental
precaution and the adaptive significance of responding to potentially
hazardous stimuli during this period.”
More
findings like these are bound to appear as researchers begin to test
pregnant and recently pregnant women on behaviors that are directly
relevant to raising a child. That pregnancy has a profound effect on the
brain and mental function of women seems increasingly certain. But the
idea that it’s a purely negative effect is a myth that’s in the process
of being debunked. Any pregnancy-related impairments are likely a side
effect of what ultimately is a maternal neuro-upgrade that boosts
women’s ability to care for their vulnerable offspring. Many will
welcome the demise of the baby-brain myth, because it’s a simplistic,
one-sided concept that almost certainly encourages prejudice against women.
This article is adapted by permission of the publisher John Wiley & Sons Ltd., from Great Myths of the Brain, by Christian Jarrett. Copyright 2014, 2015, by Christian Jarrett.
It's widely known that pregnancy changes the body, from weight gain to nausea to bizarre cravings. But becoming a mother also triggers more hidden changes, in the brain. A woman's memory, spatial skills and ability to read emotional cues change during pregnancy, and remain altered for years afterward, studies suggest.
"There are a lot of brain changes that happen during pregnancy and postpartum," said Liisa Galea, a neuroscientist at the University of British Columbia, in Canada. "It's not really surprising, given the dramatic changes in physiology, that [pregnancy] also affects the brain,"Galea told Live Science. [Blossoming Body: 8 Odd Changes That Happen During Pregnancy]
'Baby brain'
Many mothers have experienced the forgetfulness and fogging thinking during the last trimester of pregnancy or soon after giving birth, known as "baby brain," or sometimes, "pregnancy brain." Now, there's research to support the anecdotal reports of such deficits, mostly from animal studies but also some human studies. A woman's brain shrinks between 4 and 8 percent during pregnancy, Galea said.
Driving these changes is the flood of hormones pumping through a woman's body for nine months. Stress hormone levels double, progesterone levels rise 20 times higher than normal and estrogen jumps 300 times higher than normal, Galea said.
The memory and spatial navigation impairments women suffer during pregnancy may just be the brain rearranging to get ready for the arrival of a baby. Evolutionarily speaking, it doesn't make sense that a women needs terrific navigational skills around the time she's giving birth, because she needs to "stay close to the nest," Galea said. Wild animal studies show that mothers that stay near the nest produce more surviving offspring.
But "baby brain" isn't permanent, and over the long term, motherhood can actually improve brain activity.
Motherly smarts
A mother's brain returns to normal size about six months after she gives birth, Galea said. And studies in rodents suggest that mothers do better on tests of memory and multitasking than females that haven't given birth.
You wonder at how little you got done before kids, said Galea, who is a mother herself.
The research on human mothers is still unfolding, but animal studies show widespread changes throughout the brain during pregnancy and afterward, said Craig Kinsley, a neuroscientist at the University of Richmond, in Virginia.
Studies suggest that mothers become more sensitive to the sounds of babies crying, helping prepare them to care for an infant. The latest research shows that pregnant women have more right-hemisphere responses to faces, suggesting they may be more attuned to babies' emotions, Kinsley told Live Science.
And the cognitive benefits may persist throughout a mother's life, rodent studies suggest. "As the saying goes, 'once a mother, always a mother,'" Kinsley said.
But mothers aside, how does fatherhood affect a man's brain?
Fathers develop lower testosterone levels, studies show. Testosterone is linked to aggression, so reduced levels could make men better parents.
But throughout most of the animal kingdom and for most of human history, fathers have played a much smaller role in childrearing, so having children doesn't change men's brains nearly as much it does women, researchers say.
Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.
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