HOW THE BABY DEVELOPS BEFORE HE IS BORN
Now that we know something of the place where the baby’s life begins and
how the way is prepared for his growth, we are ready to follow the
interesting course of events that occur from the time the seed, a tiny
egg-like cell, bursts from an ovary until the beautiful, fully developed
baby comes into the world.
You will remember that when the ovum is expelled from an ovary it may
float about in the abdominal cavity and be lost or it may enter the
near-by mouth of a tube. Also that if it enters a tube it is carried
downward toward the uterine cavity by the sweeping motion of the
hair-like projections on the lining of the tube. This journey of the
ovum through the tube is of enormous consequence, for during its course
occur the events which decide whether the ovum shall, like most of its
fellows, be simply swept along to no end and lost, or whether by chance
it is to receive the mysterious impulse which begins the development of
a new human being. The amazing power which enables this cell to
reproduce itself, and to develop with unbelievable complexity is
acquired somewhere in the tube, usually in the upper end, by meeting and
fusing with a _spermatozoon_, the germinal cell of the male.
The spermatozoa are attracted to the ovum much as bits of metal are
drawn to a magnet, but although the ovum that is destined to be
fertilized is surrounded by several spermatozoa, only one actually
enters and fuses with it.
This fusion is termed =fertilization=, or, in lay parlance,
=conception=, and the instant at which it occurs marks the beginning of
pregnancy. The establishment of this fact is of considerable importance,
since it does away with any possible controversy concerning the time at
which a new life begins. The origin of the baby is exactly coincident
with the fusion of the male and female cells. Furthermore, the sex of
the child and any inherited traits and characteristics are also
established at this decisive moment. No amount of dieting, exercise or
mental effort on the part of the expectant mother can alter or influence
them in the smallest degree, for the father has made his complete
contribution toward the creation of the new being and the mother, also,
has made hers, except for nourishment which she provides throughout
pregnancy.
All told, probably more than five hundred theories have been advanced to
explain what it is that decides of which sex the forthcoming child is
going to be. But as the results of applying these theories have scarcely
borne out the claims of their advocates, they are given but scant
attention to-day.
The present belief regarding the causation of sex is that although there
is but one kind of ovum, there are two kinds of spermatozoa, one capable
of producing a male and the other a female child, but the
sex-determining form of the male cell that fertilizes any one ovum is a
matter of the merest chance. Statistics show that more male than female
babies are born, the usual proportion being about 105 boys to 100 girls
among those who are carried to “term” or the end of pregnancy. Among
abortions and prematurely born babies there is also a larger number of
boys than girls, but as more boys than girls die in infancy, the two
sexes about even up in the number of those living to adult life.
Concerning the time of the month when conception is most likely to
occur, there is a wide difference of opinion. Some doctors think that
the most favorable period is just before or just after menstruation,
while others believe that conception is most likely to take place about
midway between the menstrual periods.
[Illustration:
FIG. 6.—Diagram indicating process of cell division.
]
Returning to the ovum which meets a spermatozoon in the course of its
journey down the tube, we find that as soon as a spermatozoon enters an
ovum it disappears and is completely absorbed, and, as the ovum in turn
is instantly possessed of new powers, through the presence of the male
cell, the result of this union is an entirely new cell. But instead of
continuing its existence as a single cell, the fertilized ovum divides
into two cells; these two into four; the four into eight and so on until
a clustering mass of cells is formed which looks something like a
mulberry. If you will look at Fig. 6 you will see what happens as this
cell division progresses and also that in time the cells rearrange
themselves in such a way as to leave a space in the center of the mass
so that it becomes a little sac with a cluster of cells at one point,
which hangs toward the center, called the _internal cell mass_. This
will interest you because it is from cells at one point in this little
cluster that the baby begins to develop, together with the cord, bag of
waters and afterbirth, to be described later.
While these changes are taking place, the entire mass is being carried
slowly down the tube toward the uterus by the sweeping motion of the
soft little hairs on the lining of the tube. It is steadily growing, and
by the time it reaches the uterus the mass is about the size of the head
of a pin. As you will remember, the lining of the uterus prepares each
month to receive the fertilized ovum, becoming soft and thick. The cell
mass floats around for a little while after it reaches the uterine
cavity and then resting at some point, sinks down into the soft lining
and is completely buried.
From now on the cells which compose the mass rapidly increase in number
and very shortly cease to be all of one kind. These different kinds of
cells rearrange themselves and grow in such a manner that some of them
begin to form the different parts of the baby’s body and others develop
into two thin membranes that finally enclose the baby in a double sac.
He is attached to the inner surface of the sac; the space which he does
not occupy is filled with fluid and the sac itself is attached to the
uterine lining at the point where the cell mass happened to stop and
bury itself.
This sac is what you have heard called the “bag of waters,” but the
doctors refer to it as the =membranes=. As it enlarges and pushes out
into the uterine cavity it still consists of two thin membranes except
where it is attached to the uterus, at which point it grows into a
thick, spongy mass of blood-vessels. These blood-vessels divide and
branch out in a tree-like fashion and burrow into the uterine wall. As
you will see later, it is through this mass of branching blood-vessels
that the baby virtually eats and breathes and gives off waste materials
during the nine months of his life within the uterus. The doctors refer
to the mass as the =placenta= but you have heard it called the
“afterbirth,” because it is expelled after the baby is born.
[Illustration:
FIG. 7.—Diagram showing the developing baby, at an early stage, with
cord, membranes and placenta, within the uterine cavity.
]
As the baby’s development advances the part by which he is connected
with the placenta lengthens out into what is called the =umbilical
cord=. There are blood-vessels in this cord through which blood
constantly flows back and forth, carrying nourishment to the baby from
his mother and waste matter from his little body to the placenta where
it is taken up by her blood. But this exchange of materials takes place
through thin membranes and consequently the blood of the mother and baby
never mingle. Fig. 7 will give you an idea of how the sac of membranes,
with the baby hanging inside, grows out into the uterine cavity; how at
the point where the membranes are attached to the uterus the
blood-vessels have developed into the thick, spongy placenta and how the
baby is connected with it by means of the cord. In Fig. 8 you may see
how the baby changes in appearance as the weeks of pregnancy go by. At
the end of the fourth month he really looks quite like the baby that we
are so eagerly preparing for.
If we follow his development within the uterus month by month, we find
that =by the end of the first lunar month, or fourth week=, the baby’s
body is about ½ inch long and looks about as is suggested in the third
little outline in Fig. 8.
=At the end of the second month, or eighth week=, his head is fairly
well shaped; bones are beginning to develop, webbed hands and feet are
formed and the little body is about 1 inch long.
=At the end of the third month, or twelfth week=, his entire body shows
marked development and is about 3½ inches long. His fingers and toes are
separated and bear soft nails; the teeth are forming, the eyes have lids
and the umbilical cord has taken definite form.
=At the end of the fourth month, or sixteenth week=, in addition to the
development of all parts a fine, soft hair appears over the body; there
is a black, tarry substance, called _meconium_, in the baby’s intestines
and he measures about 6 inches in length and weighs perhaps ¼ pound.
[Illustration:
FIG. 8.—Appearance of the baby at different stages, early in his
development.
]
=By the end of the fifth month, or twentieth week=, the baby has grown
and developed markedly. He is now covered with skin on which are
occasional patches of a greasy, cheesy substance called _vernix
caseosa_, and though there is some fat beneath the skin his face looks
old and wrinkled. A certain amount of hair has appeared upon the head
and the eyelids are opening. It is usually during the fifth month that
the expectant mother first feels her baby move, this sensation being
commonly referred to as “quickening.” He is now about 10 inches long and
weighs about 9 ounces.
=By the end of the sixth month or twenty-fourth week=, the baby is about
12 inches long and weighs possibly 1½ pounds. He is thin and wrinkled in
appearance and if born at this time will attempt to breathe and move his
limbs but will perish in a short time.
=By the end of the seventh month, or twenty-eighth week=, he still looks
thin and scrawny; his skin is reddish and is well covered with the
cheesy vernix caseosa. If born at this stage, the baby will move quite
vigorously and cry feebly, but he is not likely to live for any length
of time. He is now about 14 inches long and weighs about 2¾ pounds.
=By the end of the eighth month, or thirty-second week=, the baby has
grown to about 17 inches in length and 4 pounds in weight, but continues
to look thin and old and wrinkled. His nails do not extend beyond the
ends of his fingers but are firmer in texture; the soft, downy hair
begins to disappear from his face but the hair on his head is more
abundant. If born at this stage, the baby will have a fair chance to
live, provided he is given painstaking care. This is true in spite of
the old belief, still widely current, that a seven months’ baby is more
likely to live than one born at eight months (meaning calendar months).
The fact is that after the twenty-eighth week the probability of the
baby’s living increases greatly with each added week of life within the
uterus. His growth during the latter part of pregnancy is rapid, for he
gains nine tenths of his weight after the fifth month and one half of
his weight during the last eight weeks of uterine life.
=At the end of the ninth month, or thirty-sixth week=, the increased
amount of fat under the baby’s skin has given a plumper, rounder contour
to the entire body; the aged look has passed and his chances for life
have greatly increased. He weighs about 5½ pounds at this stage and is
perhaps 18 inches long.
=The end of the tenth month, or fortieth week=, usually marks the end of
pregnancy. Fig. 9 will show you how the baby lies in the uterus just
before birth, curled up into the smallest possible space.
[Illustration:
FIG. 9.—The usual position of the baby just before he is born.
]
The average normally developed baby has grown to a length of about 20
inches and weighs about 7¼ pounds, boys usually being about three ounces
heavier than girls, but there may be a variation of weight among
entirely normal, healthy babies from a minimum of 5 pounds to as high as
11 pounds or more. Newborn babies very seldom weigh more than 12 pounds,
in spite of legends and rumors to the contrary.
The size of the baby is affected by the race of his parents; colored
babies, for example, averaging a smaller weight than white babies. And,
as might be expected, the size of the parents is likely to be reflected
in their infants, large parents tending to have large children and vice
versa.
The number of children which the mother has previously borne is also a
factor, since the first child is usually the smallest, the size of those
following showing an increase with the mother’s age up to her
twenty-eighth year, if her pregnancies do not occur at too frequent
intervals.
=Twins.= Sometimes a woman gives birth to more than one baby at the same
time. When there are two they are called twins; triplets when there are
three; quadruplets, quintuplets and sextuplets respectively, when there
are four, five and six babies within the uterus at once. Six is the
largest accredited number on record.
It is estimated that twins occur once in ninety pregnancies and triplets
once in about seven thousand cases. The tendency seems to be inherited,
as is evidenced by the number of twins and triplets to be found among
relatives.
Twins are often prematurely born and each is likely to be smaller than a
baby resulting from a single pregnancy, but their combined weight is
greater than the weight of one normal baby.
=Extra-uterine Pregnancy.= Another departure from the normal pregnancy
is when the baby develops outside of the uterus. Although in the normal
course of events the fertilized ovum travels down the tube and becomes
attached to the uterine lining, it is possible for it to stop, and more
or less completely develop at any point along the way. This is called an
extra-uterine pregnancy, since it occurs outside of the uterus. If the
baby develops in one of the ovaries, it is termed an ovarian pregnancy,
and a tubal pregnancy if it develops in a tube, this being the most
frequent variety of extra-uterine pregnancies. Only about one out of a
hundred such pregnancies continue throughout the allotted period, and
accordingly, a live baby, capable of living for any length of time,
seldom results.
To sum up a normal pregnancy, we find that in the course of ten lunar
months following the fertilization of an ovum, the uterus grows from a
small, flattened pelvic organ, 3 inches in length, to a large muscular
sac, about 15 inches long occupying the abdominal cavity. It increases
its weight sixteen times, that is, from 2 ounces to 2 pounds, while the
capacity of the uterine cavity is multiplied five hundred times. Within
the uterus is a baby weighing about 7¼ pounds; a placenta weighing
perhaps 1¼ pounds and approximately a quart of fluid. The baby is
attached to the placenta by means of a jelly-like cord about as thick as
one’s first finger and 20 inches long; baby, placenta, cord and fluid
all being contained in a thin, but strong sac frequently called the bag
of waters, but by the doctors termed the membranes. The total weight of
the uterus and its contents at the end of pregnancy is usually about 15
pounds.
Throughout the baby’s life within the uterus, the placenta virtually
acts as his digestive organs, lungs, kidneys and bowels. Bear this in
mind, and you will realize why, in taking care of yourself you are
taking care of your baby while his body is being built and getting
itself into running order to take up life as a separate being. The full
realization that whatever is good for you is good for your baby will
make you eager to give yourself the care that is outlined in the next
chapter.