Fetal Development
Time zero: An egg surrounded by sperm
The moment of conception.
Fertilization complete:egg with 2 nucleii
2 cell stage: about 30 minutes
4 cell stage: about 1 hour
Morula: “solid ball of cells” day 4
Blastula/Blastocyst: hollow ball of cells
Days 5-6
Gastrulation:
Day 14
Week 3
 Central nervous system begins
to develop.
Heart development initiated beating begins.
 Embryo is the size of a poppy
seed
Week 4
 The body and fetal part of
placenta are about 1” long and
the size of a pigeons egg.
 The Embryo inside is about
3/8" and weighs less than 1
gram.
 Protruding from anterior brain,
early eyes, and limb buds of
arms and legs.
nose
nose
mouth
28 days
Size of fetus at 28 days
Future eye
Future nose
Future lips and chin
Future chin
28 days
Hands and feet
4 weeks (28 days)
Week 5
 Nose and lips begin to form
 Brain is developed into 5 parts
and lumen of spinal cord is
continuous with brain vesicles
allowing free cerebral spinal
fluid flow.
 Size of an apple seed
5 weeks
5 weeks
Tail is present
5 weeks
Week 5
Week 6
 The arms, legs, and brain
continue to develop
 Lenses of the eyes appear
 Nostrils are formed
 Intestines grow as well as a
pancreas
 Size of a sweet pea
6 weeks
What do you think this will become?
If you said the hand and fingers, you were right!
Week 7
 Elbows Form
 Fingers start to develop
 Feet start to appear with tiny
notches for the toes
 Ears, eyes and nose start to
appear
 Intestines start to form in the
umbilical cord
 Teeth begin to develop under
the gums
 Embryo is the size of a
blueberry
Week 8
 Major organs begin to develop
 Cartilage and bones begin to
form
 Structure of eye is still
developing
 The tongue begins to develop
 Fingers and toes look webbed
and short
 About 1” long and 4 grams
 In males the sex hormone is
produced by the testes
8 weeks
8 weeks
8 weeks
8 weeks
Week 9





Embryo begins to move
Most joints are formed
Fingers can move
Fingerprints are shown in skin
2.3 cm in length, weighs about
2 grams
9 Weeks
9 weeks
9 week old face
Week 10
 Embryo is now called a fetus
 Eyelids are fused shut and the
irises are beginning to develop
 The placenta begins to
function
 Weighs about 4 grams
10 weeks
10 Weeks
10 weeks
10 weeks
Week 11
 Fingers and toes are now
separated
 Hair and nails begin to grow
 Size of a lime
 Genitals take on gender
specific characteristics
 Amniotic fluid begins to
accumulate
 The muscles in the intestinal
walls begin to practice
contractions that digest food.
11 Weeks
11 weeks
11 weeks
Week 12
 Vocal cords begin to form
 Ears and eyes shift to their
normal place
 Intestines move further into the
fetus
 The fetus’ liver begins to
function
 The pancreas begins to
produce insulin
 Placenta weighs more than the
fetus
Week 13
 The fetus begins to
practice inhaling and
exhaling movements
 Eyes and ears continue
to move and develop
 fetal neck is getting
longer
 All nourishment is
received from the
placenta
Week 14
 The thyroid gland has matured
and the fetus begins producing
hormones
 In boys, the prostate gland
develops
 In girls, the ovaries move from
the abdomen to the pelvis
 Bones are getting harder
 Skin is transparent
 Lanugo (very fine hair) covers
the fetal body
14 Weeks
Week 15
 Mothers can begin to feel
fluttering movements
 The three tiny bones (malleus,
incus, and stapes ) in his
middle ear have begun to
harden
 Eyebrows are beginning to
grow
 Fingernails and toe nails are
growing
15 Weeks
Week 16
 Fat cells begin to form underneath the
skin
 fetus and placenta are about the same
size
 Head and neck are held straighter
 The Heart is pumping as much as 6
gallons of blood a day and beats at a
rate about double your heart rate.
 Sucking, swallowing and blinking are
now evident and possibly hiccupping
 The fetus can now breathe
 Complete closure of nasal septum and
palate.
 Fetal heart beat heard with
amplification
 Fetal movement is recognized.
 Sex is distinguishable now.
Week 16.
16 weeks
4 months
Week 17
 He or she has a much more normal
"human" appearance now
 Pads are forming on his tiny fingertips
and toes (finger prints will soon be
apparent)
 Eyes are looking forward now
 Meconium (composed of products of
cell loss, digestive secretion and
swallowed amniotic fluid), is
accumulating in the bowel
 Umbilical cord is growing thicker and
stronger
 Male prostate begins to develop
 Skeleton begins to transform from
cartilage to bone
Week 18
 Vernix (a white cheese-like
protective material) forms on
baby's skin with the lanugo
 The placenta continues to
grow and nourish the fetus
 Tiny air sacs called alveoli
begin to form in lungs
 The vocal chords are formed
 Features of the fetal heart,
including ventricles and
chambers, should be visible
during an ultrasound
Week 19
 Nerves are being coated with a
fatty substance (myelin)
 Hair on the scalp becomes
apparent
 The milk teeth buds have
developed
 If fetus is female the uterus
starts to develop and the
vagina, uterus, and fallopian
tubes are in place.
 If it's a boy, the genitals are
distinct and recognizable
 The fetus is swallowing
amniotic fluid and his or her
kidneys are making urine.
Week 20
 The fetal heart grows stronger
 legs are reaching their relative
size
 Immunities are being
transferred
 The nerve cells for taste, smell,
hearing, seeing, and touch are
now developing
 If the fetus is a girl, her uterus
is starting to develop
 Fetal heart beat heard: 120160 beats per minute
Week 20
Week 21
 White blood cells are under
production
 Skin has changed from
translucent to become more
opaque
 Tongue is fully formed
 If the fetus is a girl, her womb
and vagina are formed.
5 months
5 Months
Week 22
 When you talk, read, or sing,
expect the fetus to hear you
 Eyelids and eyebrows are fully
formed
 the fetal brain has entered a
stage of rapid growth
 The fetal liver is starting to
break down bilirubin
 testes begin their descent to
the scrotum.
 Primitive sperm have formed
and he is producing
testosterone.
Week 23
 Proportions of the body are
now quite similar to a newborn
although thinner since he
hasn't begun to form body fat
 Bones located in the middle
ear harden
 The eyes are formed, though
the iris still lacks pigmentation
 The pancreas, essential in the
production of hormones, is
developing steadily
Week 24
 Fetus gains about 6 ounces at
week 24 of the pregnancy. The
weight is in muscle, bone
mass and organs.
 Taste buds begin to form.
 Over the next seven days the
sweat glands will be forming in
the skin.
 This week the fetus is officially
considered viable (fit to live)
Week 24
Week 25
 The structures of the spine
begin to form
 Blood vessels of the lungs
develop
 Fetal nostrils begin to open
Week 26
 Air sacs in the lungs form now
 The fetal eyes are opening and
beginning to blink
 Retinas begin to form
 Fetal brain scans show
response to touch. If you shine
a light on your abdomen, your
baby will turn his head, which
according to researchers,
means his optic nerve is
working.
Week 27
 Brain continues its rapid
growth
 Eyelids are now open more
Week 28
 Eyebrows and eyelashes are
now very noticeable
 Eyes are completely formed
 Muscle tone is improving
 Lungs are capable of breathing
now
 Fetus in breech position
Week 28.
Week 29
 fetal head is in
proportion with body
 Eyes can move
 Fetus moving from
side to side
Week 30
 Eyes can move from side to
side
 Early lanugo is beginning to
disappear
 Bone marrow is now in charge
of red blood cell production
 Fetus has the capability now to
produce tears
Week 31
 Fetus may move to the rhythm
of music
 Fat continues to accumulate
 Calcium, phosphorus and iron
are being stored and bones
are growing and hardening.
Week 32
 All five senses are working
 Toenails are completely
formed
 Should turn to head down
position.
 Skin is red and wrinkly.
Week 33
 Neurons and synapses are
developing in huge numbers
 Skull is quite pliable and not
completely joined
 If the baby is a boy, his
testicles will be descending
from his abdomen into his
scrotum
Week 34
 Eyes opened when awake and
closed when sleeping
 Fetus has learned how to blink
Week 35
 Fat accumulations plumps up
the arms and legs
 Her hearing is fully developed
 Fetus is now taking up most of
the uterus
Week 36
 This week your baby may drop
into the birth canal
 Skin is growing smooth
 Gums are very rigid
 A fully developed pair of
kidneys
Week 36
Week 36
Week 37
 Grasp is firm
 Baby turns towards light
outside the uterus
 Baby is official full term now
Week 38
 Circumference of head and
abdomen are about the same
size for the baby
 Intestines are accumulating
lots of meconium
The Third trimester
From weeks 27-39 Changes in the Mother:
*backaches *decreased BP *swelling in
ankles, hands, face *Braxton-Hicks
contractions
Bibliography
"4 Weeks Pregnant." TheBump.com. N.p., n.d. Web. 17 Sept. 2012.
<http://pregnant.thebump.com/pregnancy-week-by-week/4-weekspregnant.aspx>.
"40 Weeks Pregnant." Pregnancy Week by Week Calendar, Info and Tools.
N.p., n.d. Web. 17 Sept. 2012.
<http://www.pregnancy.org/fetaldevelopment/week-40>.
"PREGNANCY - FETAL DEVELOPMENT." PREGNANCY - FETAL
DEVELOPMENT. N.p., n.d. Web. 17 Sept. 2012.
<http://www.dcdoctor.com/pages/rightpages_wellnesscenter/pregnancy/fetalde
velopment.html>.