|
|
Milestones
of Early Life
At no time in your life does more growth and change occur than in the first nine months before birth. Here are the amazing milestones of that time in your life:
At no time in your life does more growth and change occur than in the first nine months before birth. Here are the amazing milestones of that time in your life:
Day 1: Conception: Of the
200,000,000 sperm that try to penetrate the mother’s egg cell, only one
succeeds.2 At that very moment, a new and unique individual is
formed. All of the inherited features of this new person are already set –
whether it’s a boy or girl, the color of the eyes, the color of the hair, the
dimples of the cheeks and the cleft of the chin. He or she is smaller than a
grain of sugar, but the instructions are present for all that this person will
ever become.
The first cell soon divides in two. Each of these new cells
divides again and again as they travel toward the womb in search of a protected
place to grow.3
Day 6-14:The new individual at first
attaches loosely to the wall of the womb, then burrows deeply and attaches
securely to it over the next week. Sensitive pregnancy tests can now show
positive, but this depends on the level of hormone produced by the new life. By
the end of the second week, the mother’s menstrual period is suppressed by this
hormone (hCG) which is produced by her child.4
Day 17:Blood vessels begin to
form.4 Remarkably, the future sex cells that will give rise to sperm
or eggs for a new generation begin to group together - only 17 days after this
new life is alive itself.5
Day 18-20:The foundations of the
brain, spinal cord, and nervous system are laid.6
Day 21:The heart begins to beat,7 unsurely
at first, gaining strength day by day. The heart beats 70 times per minute at
first, reaching a maximum of 170-190 at seven weeks, and slowing a bit to
160-180 at 9 weeks.8 A day later the eyes begin to develop. The
earliest stages of the ears are now present.9
Day 26-27:The lungs now begin to
form.10
Day
28-32:Two tiny arms make their appearance and budding legs follow two
days later.11 The beginnings of the mouth take shape.12
The nose starts to develop.13 The thyroid gland begins to grow. Blood
flows in the baby’s veins but stays separate from the mother’s blood. The tongue
now begins to form. The face now makes its first appearance.14
Day 36:The baby’s eyes develop their
first color in the retina (see photo above, right).15
Day 40:The baby makes her first
reflex movements. Touching around the mouth with a fine bristle causes her to
flex her neck.16
Day 41:The fingers begin to form,
followed by the toes a few days later.17
Day 42:The baby develops nerve
connections that will lead to a sense of smell. The brain is now divided into 3
parts – one to experience emotion and understand language, one for hearing and
one for seeing. 18 Joints begin to form.19 Mother now
misses second period.
Day 44:Buds of
milk teeth appear. Facial muscles develop.20 Eyelids begin to form,
protecting the developing eyes.21 Elbows take shape. Internal organs
are present, but immature. 99% of muscles are present; each with its own nerve
supply.22 Electrical activity is detectable in brain.23
Day
52:Spontaneous movement begins. The baby then develops a whole
collection of moves over the next 4 weeks including hiccupping, frowning,
squinting, furrowing the brow, pursing the lips, moving individual arms and
legs, head turning, touching the face, breathing (without air), stretching,
opening the mouth, yawning, and sucking.24 
8 Weeks:The baby is now well-proportioned, and about the
size of a thumb. Every organ is present. The liver is making blood, the kidneys
function, and the heart beats steadily. The skull, elbows, and knees are
forming. Of the 4500 structures in the adult body, 4000 are already
present.25 The skeleton of the arms and legs and the spine begins to
stiffen as bone cells are added.26
9 Weeks9 If prodded, the baby’s
eyelids and hands close. Genitalia that were forming in the 7th week now become
visible, indicating whether it’s a boy or girl. However, the doctor won’t be
able to tell by ultrasound until the 12th to 20th week. Early muscular movements
begin. The thyroid gland turns on.27
10 Weeks10 Fingerprints begin their
7 week long formation. The fingernails begin to develop. The eyelids now fuse
together until month 7, protecting the delicate eyes.28 The number of
connections between nerves and muscles has tripled since last
week.29
11 Weeks11 The baby now "practices"
breathing, since she will have to breathe air immediately after birth. The baby
urinates. Her stomach muscles can now contract.30 Vocal chords and
taste buds form.31 She can make complex facial expressions and even
smile.32
12
Weeks12 Fine hair begins to grow on the upper lip and chin and
eyebrows.33 The baby swallows and responds to skin
stimulation.32 
13 Weeks13 The face is prettier, and
facial expressions may resemble the parents’. The baby is active, but mom
doesn’t feel anything yet.34
15 Weeks15 A wild production of
nerve cells begins and continues for a month. A second surge will occur at 25
weeks.35
4
MonthsNostrils and toenails become visible. The baby may suck her
thumb, turn somersaults and has a firm grip. The ovaries of girls contain
beginnings of eggs. She begins to develop sleeping habits.32 At about
4 ½ months she is able to experience pain.36, 37
5
MonthsThe testes descend in boys. Mom may feel the baby kick, turn or
hiccup and may be able to identify a bulge as an elbow or head.38
Each side of the brain has a billion nerve cells now.36
6 MonthsThe baby will be able to
hear by next week.39 The child sleeps and wakes, nestling in her
favorite positions to sleep, and stretches upon waking up.40
7 MonthsThe eyelids begin to reopen,
preparing to see the outside world.41 Eyelashes have now become well
developed.42
8 MonthsSkin becomes pink and
smooth. The pupils of eye respond to light. Fingernails reach to the tip of the
finger.42 The baby is really getting cramped now.
9.5 MonthsThe child triggers labor
and birth occurs, an average of 264-270 days after conception.43
And not until the baby has gone through all these events on the
inside can we see the new child on the outside.
Carnegie Developmental Stages, developed by Streeter and
O’Rahilly, are used universally to categorize the growth of the embryo into 23
stages during the first 8 weeks of life. Carnegie Stages are based on morphology
- the form and structures within of the embryo. From embryo to embryo, the days
required to get to each stage can vary slightly. Also, O’Rahilly has suggested
some changes in the days relating to each stage due to in vivo ultrasound
studies.
43 Selected differences as
reported by O’Rahilly are detailed below.
Primary References:
?Carlson, B., Human Embryology & Developmental Biology,
Toronto: Mosby Publication; 3rd edition, 2004.
?Moore, K. and Persaud, T., The Developing Human, Clinically
Oriented Embryology, 6th Edition, Philadelphia: W.B. Sanders, 1998.
?O’Rahilly, R. and Muller, F., Human Embryology and Teratology,
3rd Edition, New York: John Wiley and Sons, Inc., 2001.
?Tsiaras, A. and Werth, B., From Conception to Birth, a Life
Unfolds, New York: Doubleday, 2002.
1
. Age in this brochure is given two ways: 1) days after
fertilization or days from conception given by the top red number, and 2) days
from last menstrual period, or LMP for short, given by the lower red number.
Doctors use "LMP" because it is hard to know just when conception occured. Here,
we emphasize the age of the new life as it unfolds. Add 14 days to
post-fertilization days to convert to the LMP days.
2.
"Life Before Birth," Life Magazine, Apr. 30, 1965, p. 13.
3. Moore, K. and Persaud, T., p. 37-45.
4.
Moore, K. and Persaud, T., p. 42-48, 76. 5.
O’Rahilly, R. and Muller, F., p. 23.
6.
Mitchell, B and Sharma, R., Embryology , New York:
Churchill Livingstone, Dec. 2004, p. 4. Note: Carlson and Moore concur that the
neural plate, fold and groove are forming around 18-20 days. O’Rahilly puts this
at 24-25 days from in vivo ultrasound results.
7.
Estimates vary for when the heart begins to beat: 21-22
days, Moore, K. and Persaud, T., p. 77; at least by 23 days from
transvaginal ultrasound results, O’Rahilly, R. and Muller, F., p. 183; 21-22
days, Carlson, B., p. 117; 18 days, Tanner, J. and Taylor, G. and the
editors of Time-Life Books, Growth, New York: Life Science Library, 1965, p. 64
(a 40 year old source).
No comments:
Post a Comment