This document outlines the key stages of prenatal development from conception through birth in 3 months increments. It describes the physical changes that occur each week, including organ formation, growth in length and weight, and developing abilities. The major stages are the zygote (conception to implantation), embryo (implantation through 8 weeks), and fetus (9 weeks through birth). Development progresses from basic cell division and organ formation in the first trimester to further physical maturation and growth in the second and third trimesters.

1. Prenatal Development

2. Directions
Read through this Powerpoint and
compare to your prenatal webquest you
completed last week. Use both
resources to compile a prenatal
development timeline for the baby
*we will add what mom goes through later

3. The Three Stages of evelopment
 Zygote
– Conception through Implantation
• Implantation occurs approximately 2 weeks after
conception
 Embryo
– Implantation through the 8th week
 Fetus
– 9th week through Birth

4. The 1st Trimester
Months 1-3
Weeks 1-13

5. Week 3 - Conception
 Conception is the
moment when the
sperm and egg
unite.
 This begins the
zygote stage.
– Conception thru
implantation
 Now there is an
increased risk for an
ectopic pregnancy.

6. Week 4
 There are three layers to your baby
– ectoderm, mesoderm, and endoderm
– These layers will form the baby’s organs & tissues
– Arm and leg buds begin developing, but are not
clearly distinguishable.
 The placenta has also begun to form and is
producing important hormones including hCG.
 There is movement of rudimentary blood
through the main vessels.

7. 4 Weeks

8. The Heartbeat
 A fetus’sheart begins to beat 21 days
after conception.
 Normal range of a fetal heartbeat is
120-160 beats per minute.
 http://www.gravityteen.com/prenatal/ninem

9. Week 5
 Baby looks more like a tadpole
– Their heart is beating steadily
– Eyes and ears are beginning to form
– Skeleton is forming
– They are 1/4 inch long

10. 5 Weeks

11. Week 6
 Baby
– Lungs, nose and jaw are beginning to form.
– Hands and feet have web like structures that
will become fingers and toes.
– 1/2 inch long.

12. 6 Weeks

13. Week 7
 Essential organs are forming.
 Hair follicles, eyelids and tongue are
forming.
 Elbows and toes are more visible.
 Approximately 3/4 of an inch long and
weighing less than an aspirin.

14. 7 Weeks

15. Week 8
 Baby:
– Everything that is present in an adult human
is present in the embryo.
– Gender has been determined, but external
genitalia cannot be seen.
• “indifferent penis”
– Brain takes control of body systems.

16.  The amniotic sac filled with fluid forms
around the baby
 Amniotic fluid protects the embryo and
cushions it from any falls or bumps
mom may have
 The placenta develops
– The placenta is full of blood vessels that
carry food and oxygen to the baby through
the umbilical cord.

17. Umbilical Cord
 Brings nourishment to the baby and
takes waste away
 It is firm – like a garden hose full of water
 Generally not flexible enough to loop
around the fetus, but may occur

18. End of Month Two

19. Week 9
 Eyelids are fused shut
and will stay that way
until week 28.
 All joints are working –
knees, elbows, etc.
 Baby can make a fist
and suck their thumb.
 Baby is about the size
of a grape.

20. Week 10
 Baby can squint, swallow,
and frown.
 Fingernails, toenails, and
hair become visible this
week.
 Baby is actively
swallowing amniotic fluid.
 Baby is about the size of
a lime.

21. Week 11
 Baby begins to urinate
 Baby can smile
 Bones are beginning
to harden.
 Baby is very active
even though you can’t
feel them yet.

22. Week 12
 Baby can kick, curl and fan their toes,
make a fist, move their thumbs, bend
their wrists, turn their head, open their
mouth and press their lips together.
 Baby practices breathing.
 The spinal column becomes bony.
 Baby is 3 inches long and weighs 1
ounce.

23. 12 Weeks

24. Week 13
 Your facial expressions
start to resemble your
parents'.
 Your movements are
graceful and reflexes
vigorous.
 Vocal chords are
formed, but without air,
you can't yet cry.
 Sex organs are
apparent.

25. End of Month Three

26. End of the 1st Trimester

27. 2nd Trimester
Months 3-6
Weeks 14-26

28. Week 14
 Babies heart pumps several
quarts of blood.
 Fine hair has grows on their
head.
 Nails are well formed.
 The growth of the head
slows down and the rest of
their body catches up.
 The neck is formed.
 Legs and arms lengthen.
 Baby is 4 inches long and
weighs less than 2 ounces.

29. Week 15
 Baby
– 5 inches long and weighs 2 ounces.
– Ears are beginning to look normal
– Eyes are moving to the front of the head

30. Week 16
 Baby
– 6 inches long and weighs 2 1/2 ounces.
– Head, neck and spine curve to follow the circular
space of the uterus. Baby now occupies all the
room in Mom's pelvis.
– The first thin transparent layer of skin begins to
replace the temporary protective membrane.
– Their eyes are still closed and the nose, eyes and
lips and ears are shaping up.
– The sex is discernible on ultrasound.

32. Week 17
 Baby
– 6.5 inches long and weighing 4 ounces
– Sense of hearing is fully developed
– Fat tissue is forming
• Regulates body temperature and metabolism

33. Week 18
 Baby
– 7 inches long and 5.5 ounces
– Protective coating is forming around baby’s nerves

34. Week 19
 Baby
– 7.5 inches long and weighs 7 ounces
– Hair is beginning to grow
– If you are having a girl, she already has 6
million eggs formed in her ovaries.

35. Week 20 – The Halfway Point
 Baby is about 8 inches
long and weigh about 9
ounces.
 Baby can pedal their
legs, make crawling
movements, roll over,
turn somersaults and
swim.
 Covered with vernix
which helps protect
their skin.

36. Week 21
 Baby
– 8.5 inches long and 12 ounces
– Actively swallowing amniotic fluid

37. Week 22
 9 inches long and 14
ounces.
 Taken on the form of a
tiny newborn.
 Now you can lift your
eyes to eye level and
turn them slowly from
side to side for long
periods of time.
 Your eyes can also dart
quickly back and forth,
sometimes smoothly,
sometimes jerkily.

38. Week 23
 Baby
– Finally 1 pound and 10 inches long

39. Week 24
 Baby
– Brain is growing rapidly
– Taste buds are forming
– Lungs are developing
• Produce surfactant which allows the air sacs to
inflate easily

40. Week 25
 Baby
– Oil and sweat glands are functioning.
– Baby can open their eyes when the eyelids become
unsealed. They scan the darkness and may blink if
there is a sudden noise.
– They drink the amniotic fluid and could survive
outside the womb if born early.
– www.gravityteen.com/prenatal/ninemonths.cfm
• Month 6

41. Week 26
 Baby
– 13 inches long and 2 pounds
– Development may seem insignificant at
this point, but baby is maturing to survive in
the world

42. End of 2nd Trimester

43. 3rd Trimester
Months 7-9
Weeks 27-40

44. Week 27
 Baby
– 14 inches long and 2.25 pounds
– Has a regular sleep cycle
• Unfortunately it’s not the same as yours!

45. Week 28
 Baby
– 14.25 inches long and 2.5 pounds
• Remember, baby gains the most weight in the
last few weeks
– Indentions start to form in baby’s brain
– Eyebrows and eyelashes are visible

46. Week 29
 Baby
– 14.5 inches long and 2.75 pounds
– Brain, muscles and lungs are maturing
rapidly

47. Week 30
 Baby
– Using all four of your senses: vision,
hearing, taste and touch.
– Recognize Mom's voice.
– There is still enough space to straighten out.
– The amniotic fluid is reduced by half to allow
you room to grow.
– Gaining weight quickly and by the end of the
seventh month may weigh 4 pounds.

48. Week 31
 Baby
– 15 inches long and 3.5 to 4 pounds

49. Week 32
 Baby
– Skeleton is formed but bones are still soft
– 15 to 17 inches long and 4 to 4.5 pounds

50. Week 33
 Baby
– Bones are hardening except for the skull

51. Week 34
 Baby
– 15.5 to 17.5 inches long and 5 to 5.5 pounds
– High survival rate if born at this point

52. Week 35
 Baby
– Skin is beginning to thicken with a layer of
fat stored underneath for insulation and
nourishment.
– Antibodies are building up.
– Developed taste buds seem to have given
them a sweet tooth.
– Responding to familiar noises such as
Mom's voice and music.
– Will gain two more pounds this month.

54. Week 36
 Baby
– 16 - 19 inches long and 5.75 - 6.75 pounds
– Lanugo and vernix are starting to disappear
• Baby swallow this along with amniotic fluid to
produce meconium, or baby’s first bowel
– Should be in the head down position

55. Week 37
 Baby
– Considered full term
– Should be head down
• Breech birth happens for 1 in 25 births

56. Week 38
 Baby
– 17-20 inches long and 6.25 to 7.5 pounds
– Usually born with brown or blue eyes
• If the eyes are blue, they may change by the
time baby is 9 months old

57. End of 3rd Trimester