Life Before Birth
By DR. HERBERT THOMS and BRUCE BLIVEN, JR.
From
conception to birth, the growth of a baby proceeds with astonishing speed. In the first month alone the tiny organism
increases to nearly ten thousand times its initial weight. In the first three months it progresses from
a speck of watery material to an infinitely complicated human form—unfinished,
to be sure, but recognizably a baby-to-be.
The whole process is a marvel of refinement that staggers the
imagination. One change prepares the
way for the next, and the plan, for all its subtlety, is marked by incredible
accuracy. This transformation, taking
about 267 days, is the unbelievable manner in which one’s own, and everybody’s,
biography begins.
At
conception the male sperm joints the female egg, and immediately the 48
chromosomes in the nucleus of this completed cell begin to churn about, a
prelude to the first cell division. The
fertilized egg is approximately as big as the dot over this “i”. Yet physically present within it are all the
genetic characteristics that will make this the particular child of a
particular family—John Smith, Jr. let’s say, with his father’s blue eyes and
his maternal grandmother’s aptitude for music.
As cell
divides [splitting into two, the two becoming four, and so on] the egg floats
down through one of the two Fallopian tubes to the womb, a two=inch journey
that takes three to four days. By the
time it reaches the womb the egg is usually about its 16-cell
stage. Even at this early date a
mysterious development has taken place.
There are now two markedly different kinds of cells: flat, fast dividing
cells that form the delicate outer layer, and slow-dividing inner cells which
are plump and roundish.
From the
fourth to the sixth or seventh day the egg-ball, now about the size of a
pinhead, floats in the warm, dark, fluid filled womb cavity. The velvety lining of the womb, interlaced
with small blood vassals, has become extraordinarily soft and thick, as it does
once every 28 days during the mother’s childbearing years. On about the seventh day, as the egg drifts
against this lining, it begins to burrow vigorously into the spongy material
and completely embeds itself, opening up some of the hair like capillaries in
the process and releasing the blood inside them. Now, all over its surface, the egg-ball sprouts tiny,
fast-growing projections called “villi”—many hundreds of them. Lied minute plant roots, they dip into the
infinitesimal pools of blood and absorb oxygen and food-minerals,
carbohydrates, proteins, fats. With
food, the egg-ball frowns quickly.
All
these events have taken place before the mother knows she is pregnant; chances
are she will not find out about it before 21st day at the earliest.
Inside
the sphere, meanwhile, the colony of round cells has formed itself into two
tiny sacs, the yolk sac and the amnion.
Where the sacs touch, they interact and produce a third layer of
cells—making a three-layered disk. The
rest of the yolk sac will not be important in future, though the amnion remains
a key structure until delivery. But the
three-layer cellular disk now has the star part, for it is about to transform
itself into the embryo.
Each
layer will provide the baby-to-be with material for specific kinds of
tissues. One is the source for the cells
that will form its nervous system, skin, hair, fingernails, tooth enamel and
the linings of its nose and throat. The
middle layer will supply cells for the baby’s muscles, bones and cartilage,
blood vessels, kidneys ad tooth dentine.
The third layer will provide the digestive tract and most of the
respiratory system.
The next
transformation is, perhaps, the most miraculous of all. About the 19th or 20th
day the disk develops a groove like crease down one of its surfaces, with
ridges on either side. The ridges
converge at one end—that is to be the head.
As the ridges rise and fold towards each other, the disk becomes partly
tubular and crescent-shaped. The
outside curve will become the baby’s back.
In a few days the first suggestion of the spinal column will appear, and
the brain matter will start to fill the hollow at the head end. Small buds, the first hind of arms and legs,
are due shortly. By the 21st
day a rudimentary heart has formed. Ten
days later it has started to beat.
The
embryo is connected with the casings of the sphere by a thread of cells, which
will in time lengthen into a dull white 22-inch rope-the umbilical chord. Enclosed within the amniotic sac as well,
the embryo is doubly wrapped—a minute crescent inside a tissue bag inside a
tissue ball buried in the spongy womb lining.
Moreover, the sac is filled with a clear watery liquid which is an
effective shock absorber—pregnant women have been in hair-raising accidents
without losing their babies.
From now
on the embryo quickly takes on a babyish appearance. By the end of the second month it is only one inch long from head
of rump, but it has a nose, mouth, ears and a suggestion of what will become
eye sockets.
By the
end of the third month the embryo—from now on called a “fetus”—is three inches
long and about one ounce in weight. Its
various body systems show faintly what they are soon to become. Eyes and eyelids are formed, though, for the
time being, they are closed. Sexual
organs are present. Arms and legs are
complete down to finger and toenails, and the fetus has started to move them,
although this first movement is imperceptible to the mother.
Its
heart has been beating for two months, gaining muscular strength. The fetus has also begun to swallow small
amounts of the amniotic fluid, an exercise not only in swallowing but also in
something like breathing. The liquid
enters its lungs, and then the fetus expels it, using the breathing
muscles. It is now just practice; until
birth the fetus gets all its oxygen and food from the mother’s blood.
All
these astonishing developments have taken place in just the first three
months. The mother’s womb has enlarged
nut, except perhaps to he own eyes, the swelling of her abdomen is still
negligible. For the next six months,
while the fetus grows to baby size, its ability to function as a newborn will
develop gradually.
The
umbilical chord is the only connection between the mother and fetus. The chord contains no nerves, and since the
nervous system of mother and fetus are entirely separate, nothing the mother
thinks or perceives can affect her offspring.
This is why the age-old supersistitions about prenatal influence are
false.
As with
its nervous system, the fetus’ circulatory system is entirely independent. The fetus manufactures all its own blood,
which never mixes with that of its mother.
The two blood streams simply exchange materials inside a remarkable
organ called the placenta, which develops in the womb during pregnancy and is
expelled at the end of the birth process.
The placenta, which is connected to the fetus by umbilical cord, is
shaped like a flat cake five or six inches in diameter. Most of this bulk is made up of villi,
equipped now with blood vessels and intermeshed with digests on the fetus’
behalf an incalculably valuable service, for it allows the future baby’s
respiratory and digestive systems to remain latent while they grow.
Toward
the latter part of the fourth month the mother feels the fetus moving. This ‘quickening” is at first very faint;
weeks my elapse before the flexing of the fetus’ arms and legs become
unmistakably strong. Now, halfway
through the pregnancy, the fetus is six inches long and weighs six ounces. Eyebrows and eyelashes have appeared. For the first time the heartbeat is strong
enough to be heard with a stethoscope.
It beats about 136 times a minute, almost twice as fast as the mother’s
heart. One additional milestone; a
discernible amount of calcium has now been deposited in the fetus’ soft,
gristle like bones.
By the
end of the sixth month the fetus is a foot long, weighs about a pound and a
half. It can hiccup, move its facial
muscles and sneeze. Its eyes are almost
fully developed, but at best are sensitive only to light. If fetus were born now, it might survive,
but the chance is exceedingly remote.
Gaining
dramatically in strength, the fetus now stretches and squirms, moving not only
its arms and legs but also its body and head.
Its chest muscles, in preparation for breathing air, grow stronger every
day. Its kidneys are working and its
intestines are active despite the fact that normally there will be no
evacuation until after the delivery.
Rehearsing the reflex action that after birth will provide food, and
fetus is making sucking motions more of less constantly. In fact, it may vary well be sucking its
thumb, as some babies do before they are born.
Toward
the end of the end of the ninth month, of on about the 252nd day,
the fetus is “mature,” ready to born.
The 267-day figures are only a statistical average; 15-day variations
either way are commonplace.
The
mature fetus usually weighs something between six and seven pounds; it is close
to 19 inches tall. Its arms are folded
across its chest and its thighs drawn up against the stomach, a position that
takes up the least possible space. Most
of the time it is quiet [and presumably in a state very much like sleep], but
now when it thrusts its arms or legs the movements are really powerful. If the doctor places the palm of his hand
over the womb, the fetus is likely to answer with blows of protest.
This is a small but complete human being. Any day now he will face his first great
ordeal, the process of being born.
Everything for him is in a sense still to come. And yet no one would deny that his
experience already has been a truly marvelous one.
