By Janet L. Hopson, published on September 1, 1998 - last reviewed on June 9, 2016
Behaviorally speaking, there's little difference between a newborn
baby and a32-week-old fetus. A new wave of research suggests that the
fetus can feel, dream, even enjoy The Cat in the Hat. The abortion debate
may never be the same.
The scene never fails to give goose bumps: the baby, just seconds
old and still dewy from the womb, is lifted into the arms of its
exhausted but blissful parents. They gaze adoringly as their new child
stretches and squirms, scrunches its mouth and opens its eyes. To anyone
watching this tender vignette, the message is unmistakable. Birth is the
beginning of it all, ground zero, the moment from which the clock starts
Not so, declares Janet DiPietro. Birth may be a grand occasion,
says the Johns Hopkins University psychologist, but "it is a trivial
event in development. Nothing neurologically interesting happens."
Armed with highly sensitive and sophisticated monitoring gear,
DiPietro and other researchers today are discovering that the real action
starts weeks earlier. At 32 weeks of gestation--two months before a baby
is considered fully prepared for the world, or "at term" --a fetus is
behaving almost exactly as a newborn. And it continues to do so for the
next 12 weeks.
As if overturning the common conception of infancy weren't enough,
scientists are creating a startling new picture of intelligent life in
the womb. Among the revelations:
o By nine weeks, a developing fetus can hiccup and react to loud
noises. By the end of the second trimester it can hear.
o Just as adults do, the fetus experiences the rapid eye movement
(REM) sleep of dreams.
o The fetus savors its mother's meals, first picking up the food
tastes of a culture in the womb.
o Among other mental feats, the fetus can distinguish between the
voice of Mom and that of a stranger, and respond to a familiar story read
o Even a premature baby is aware, feels, responds, and adapts to
o Just because the fetus is responsive to certain stimuli doesn't
mean that it should be the target of efforts to enhance development.
Sensory stimulation of the fetus can in fact lead to bizarre patterns of
adaptation later on.
The roots of human behavior, researchers now know, begin to develop
early--just weeks after conception, in fact. Well before a woman
typically knows she is pregnant, her embryo's brain has already begun to
bulge. By five weeks, the organ that looks like a lumpy inchworm has
already embarked on the most spectacular feat of human development: the
creation of the deeply creased and convoluted cerebral cortex, the part
of the brain that will eventually allow the growing person to move,
think, speak, plan, and create in a human way.
At nine weeks, the embryo's ballooning brain allows it to bend its
body, hiccup, and react to loud sounds. At week ten, it moves its arms,
"breathes" amniotic fluid in and out, opens its jaw, and stretches.
Before the first trimester is over, it yawns, sucks, and swallows as well
as feels and smells. By the end of the second trimester, it can hear;
toward the end of pregnancy, it can see.
Scientists who follow the fetus's daily life find that it spends
most of its time not exercising these new abilities but sleeping. At 32
weeks, it drowses 90 to 95% of the day. Some of these hours are spent in
deep sleep, some in REM sleep, and some in an indeterminate state, a
product of the fetus's immature brain that is different from sleep in a
baby, child, or adult. During REM sleep, the fetus's eyes move back and
forth just as an adult's eyes do, and many researchers believe that it is
dreaming. DiPietro speculates that fetuses dream about what they
know--the sensations they feel in the womb.
Closer to birth, the fetus sleeps 85 or 90% of the time the same as
a newborn. Between its frequent naps, the fetus seems to have "something
like an awake alert period," according to developmental psychologist
William Filer, who with his Columbia University colleagues is monitoring
these sleep and wakefulness cycles in order to identify patterns of
normal and abnormal brain development, including potential predictors of
sudden infant death syndrome. Says Filer, "We are, in effect, asking the
fetus: 'Are you paying attention? Is your nervous system behaving in the
Awake or asleep, the human fetus moves 50 times or more each hour,
flexing and extending its body, moving its head, face, and limbs and
exploring its warm wet compartment by touch. Heidelise Als, a
developmental psychologist at Harvard Medical School, is fascinated by
the amount of tactile stimulation a fetus gives itself. "It touches a
hand to the face, one hand to the other hand, clasps its feet, touches
its foot to its leg, its hand to its umbilical cord," she reports.
Als believes there is a mismatch between the environment given to
preemies in hospitals and the environment they would have had in the
womb. She has been working for years to change the care given to preemies
so that they can curl up, bring their knees together, and touch things
with their hands as they would have for weeks in the womb.
Along with such common movements, DiPietro has also noted some
odder fetal activities, including "licking the uterine wall and literally
walking around the womb by pushing off with its feet." Laterborns may
have more room in the womb for such maneuvers than first babies. After
the initial pregnancy, a woman's uterus is bigger and the umbilical cord
longer, allowing more freedom of movement. "Second and subsequent
children may develop more motor experience in utero and so may become
more active infants," DiPietro speculates.
Fetuses react sharply to their mother's actions. "When we're
watching the fetus on ultrasound and the mother starts to laugh, we can
see the fetus, floating upside down in the womb, bounce up and down on
its head, bum-bum-bum, like it's bouncing on a trampoline," says
DiPietro. "When mothers watch this on the screen, they laugh harder, and
the fetus goes up and down even faster. We've wondered whether this is
why people grow up liking roller coasters."
Why people grow up liking hot chilies or spicy curries may also
have something to do with the fetal environment. By 13 to 15 weeks a
fetus' taste buds already look like a mature adult's, and doctors know
that the amniotic fluid that surrounds it can smell strongly of curry,
cumin, garlic, onion and other essences from a mother's diet. Whether
fetuses can taste these flavors isn't yet known, but scientists have
found that a 33-week-old preemie will suck harder on a sweetened nipple
than on a plain rubber one.
"During the last trimester, the fetus is swallowing up to a liter a
day" of amniotic fluid, notes Julie Mennella, a biopsychologist at the
Monell Chemical Senses Center in Philadelphia. She thinks the fluid may
act as a "flavor bridge" to breast milk, which also carries food flavors
from the mother's diet.
Whether or not a fetus can taste, there's little question that it
can hear. A very premature baby entering the world at 24 or 25 weeks
responds to the sounds around it, observes Als, so its auditory apparatus
must already have been functioning in the womb. Many pregnant women
report a fetal jerk or sudden kick just after a door slams or a car
Even without such intrusions, the womb is not a silent place.
Researchers who have inserted a hydrophone into the uterus of a pregnant
woman have picked up a noise level "akin to the background noise in an
apartment," according to DiPietro. Sounds include the whooshing of blood
in the mother's vessels, the gurgling and rumbling of her stomach and
intestines, as well as the tones of her voice filtered through tissues,
bones, and fluid, and the voices of other people coming through the
amniotic wall. Fifer has found that fetal heart rate slows when the
mother is speaking, suggesting that the fetus not only hears and
recognizes the sound, but is calmed by it.
Vision is the last sense to develop. A very premature infant can
see light and shape; researchers presume that a fetus has the same
ability. Just as the womb isn't completely quiet, it isn't utterly dark,
either. Says Filer: "There may be just enough visual stimulation filtered
through the mother's tissues that a fetus can respond when the mother is
in bright light," such as when she is sunbathing.
Japanese scientists have even reported a distinct fetal reaction to
flashes of light shined on the mother's belly. However, other researchers
warn that exposing fetuses (or premature infants) to bright light before
they are ready can be dangerous. In fact, Harvard's Als believes that
retinal damage in premature infants, which has long been ascribed to high
concentrations of oxygen, may actually be due to overexposure to light at
the wrong time in development.
A six-month fetus, born about 14 weeks too early, has a brain that
is neither prepared for nor expecting signals from the eyes to be
transmitted into the brain's visual cortex, and from there into the
executive-branch frontal lobes, where information is integrated. When the
fetus is forced to see too much too soon, says Als, the accelerated
stimulation may lead to aberrations of brain development.
Along with the ability to feel, see, and hear comes the capacity to
learn and remember. These activities can be rudimentary, automatic, even
biochemical. For example, a fetus, after an initial reaction of alarm,
eventually stops responding to a repeated loud noise. The fetus displays
the same kind of primitive learning, known as habituation, in response to
its mother's voice, Fifer has found.
But the fetus has shown itself capable of far more. In the 1980s,
psychology professor Anthony James DeCasper and colleagues at the
University of North Carolina at Greensboro devised a feeding contraption
that allows a baby to suck faster to hear one set of sounds through
headphones and to suck slower to hear a different set. With this
technique, DeCasper discovered that within hours of birth, a baby already
prefers its mother's voice to a stranger's, suggesting it must have
learned and remembered the voice, albeit not necessarily consciously,
from its last months in the womb. More recently, he's found that a
newborn prefers a story read to it repeatedly in the womb--in this case,
The Cat in the Hat--over a new story introduced soon after birth.
DeCasper and others have uncovered more mental feats. Newborns can
not only distinguish their mother from a stranger speaking, but would
rather hear Mom's voice, especially the way it sounds filtered through
amniotic fluid rather than through air. They're xenophobes, too: they
prefer to hear Mom speaking in her native language than to hear her or
someone else speaking in a foreign tongue.
By monitoring changes in fetal heart rate, psychologist JeanPierre
Lecanuet and his colleagues in Paris have found that fetuses can even
tell strangers' voices apart. They also seem to like certain stories more
than others. The fetal heartbeat will slow down when a familiar French
fairy tale such as "La Poulette" ("The Chick") or "Le Petit Crapaud"
("The Little Toad") is read near the mother's belly. When the same reader
delivers another unfamiliar story, the fetal heartbeat stays
The fetus is likely responding to the cadence of voices and
stories, not their actual words, observes Fifer, but the conclusion is
the same: the fetus can listen, learn, and remember at some level, and,
as with most babies and children, it likes the comfort and reassurance of
It's no secret that babies are born with distinct differences and
patterns of activity that suggest individual temperament. Just when and
how the behavioral traits originate in the womb is now the subject of
In the first formal study of fetal temperament in 1996, DiPietro
and her colleagues recorded the heart rate and movements of 31 fetuses
six times before birth and compared them to readings taken twice after
birth. (They've since extended their study to include 100 more fetuses.)
Their findings: fetuses that are very active in the womb tend to be more
irritable infants. Those with irregular sleep/wake patterns in the womb
sleep more poorly as young infants. And fetuses with high heart rates
become unpredictable, inactive babies.
"Behavior doesn't begin at birth," declares DiPietro. "It begins
before and develops in predictable ways." One of the most important
influences on development is the fetal environment. As Harvard's Als
observes, "The fetus gets an enormous amount of 'hormonal bathing'
through the mother, so its chronobiological rhythms are influenced by the
mother's sleep/wake cycles, her eating patterns, her movements."
The hormones a mother puts out in response to stress also appear
critical. DiPietro finds that highly pressured mothers-to-be tend to have
more active fetuses--and more irritable infants. "The most stressed are
working pregnant women," says DiPietro. "These days, women tend to work
up to the day they deliver, even though the implications for pregnancy
aren't entirely clear yet. That's our cultural norm, but I think it's
Als agrees that working can be an enormous stress, but emphasizes
that pregnancy hormones help to buffer both mother and fetus. Individual
reactions to stress also matter. "The pregnant woman who chooses to work
is a different woman already from the one who chooses not to work," she
She's also different from the woman who has no choice but to work.
DiPietro's studies show that the fetuses of poor women are distinct
neurobehaviorally-less active, with a less variable heart rate--from the
fetuses of middle-class women. Yet "poor women rate themselves as less
stressed than do working middle-class women," she notes. DiPietro
suspects that inadequate nutrition and exposure to pollutants may
significantly affect the fetuses of poor women.
Stress, diet, and toxins may combine to have a harmful effect on
intelligence. A recent study by biostatistician Bernie Devlin, of the
University of Pittsburgh, suggests that genes may have less impact on IQ
than previously thought and that the environment of the womb may account
for much more. "Our old notion of nature influencing the fetus before
birth and nurture after birth needs an update," DiPietro insists. "There
is an antenatal environment, too, that is provided by the mother."
Parents-to-be who want to further their unborn child's mental
development should start by assuring that the antenatal environment is
wellnourished, low-stress, drug-free. Various authors and "experts" also
have suggested poking the fetus at regular intervals, speaking to it
through a paper tube or "pregaphone," piping in classical music, even
flashing lights at the mother's abdomen.
Does such stimulation work? More importantly: Is it safe? Some who
use these methods swear their children are smarter, more verbally and
musically inclined, more physically coordinated and socially adept than
average. Scientists, however, are skeptical.
"There has been no defended research anywhere that shows any
enduring effect from these stimulations," asserts Filer. "Since no one
can even say for certain when a fetus is awake, poking them or sticking
speakers on the mother's abdomen may be changing their natural sleep
patterns. No one would consider poking or prodding a newborn baby in her
bassinet or putting a speaker next to her ear, so why would you do such a
thing with a fetus?"
Als is more emphatic. "My bet is that poking, shaking, or otherwise
deliberately stimulating the fetus might alter its developmental
sequence, and anything that affects the development of the brain comes at
Gently talking to the fetus, however, seems to pose little risk.
Fifer suggests that this kind of activity may help parents as much as the
fetus. "Thinking about your fetus, talking to it, having your spouse talk
to it, will all help prepare you for this new creature that's going to
jump into your life and turn it upside down," he says--once it finally
makes its anti-climactic entrance.
WHAT'S THE IMPACT ON ABORTION?
Though research in fetal psychology focuses on the last trimester,
when most abortions are illegal, the thought of a fetus dreaming,
listening and responding to its mother's voice is sure to add new
complexity to the debate. The new findings undoubtedly will strengthen
the convictions of right-to-lifers--and they may shake the certainty of
pro-choice proponents who believe that mental life begins at
Many of the scientists engaged in studying the fetus, however,
remain detached from the abortion controversy, insisting that their work
is completely irrelevant to the debate.
"I don't think that fetal research informs the issue at all,"
contends psychologist Janet DiPietro of Johns Hopkins University. "The
essence of the abortion debate is: When does life begin? Some people
believe it begins at conception, the other extreme believes that it
begins after the baby is born, and there's a group in the middle that
believes it begins at around 24 or 25 weeks, when a fetus can live
outside of the womb, though it needs a lot of help to do so.
"Up to about 25 weeks, whether or not it's sucking its thumb or has
personality or all that, the fetus cannot survive outside of its mother.
So is that life, or not? That is a moral, ethical, and religious
question, not one for science. Things can behave and not be alive.
Right-to-lifers may say that this research proves that a fetus is alive,
but it does not. It cannot."
"Fetal research only changes the abortion debate for people who
think that life starts at some magical point," maintains Heidelise AIs, a
psychologist at Harvard University. "If you believe that life begins at
conception, then you don't need the proof of fetal behavior." For others,
however, abortion is a very complex issue and involves far more than
whether research shows that a fetus is alive. "Your circumstances and
personal beliefs have much more impact on the decision," she
Like DiPietro, AIs realizes that "people may use this research as
an emotional way to draw people to the pro-life side, but it should not
be used by belligerent activists." Instead, she believes, it should be
applied to helping mothers have the healthiest pregnancy possible and
preparing them to best parent their child. Columbia University
psychologist William Fifer agrees. "The research is much more relevant
for issues regarding viable fetuses--preemies."
Simply put, say the three, their work is intended to help the
babies that live--not to decide whether fetuses should.