1. Pregnancy and Birth
Prenatal Development

2. Objectives: To name the three stages of pregnancy
Describe the prenatal development during each of the three stages of pregnancy
Describe how the embryo is protected and nourished
Describe the stages of childbirth

3. What Happens Before Birth?
When an egg leaves the ovary, it is covered by a protective layer of cells

4. What Happens Before Birth?
The Fallopian tube is lined with a layer of cilia to help move the egg down to the uterus.

5. What Happens Before Birth?
Sperm swim through the cervix and uterus and into a fallopian tube to meet an egg.

6. What Happens Before Birth?
Sperm secrete an enzyme the erodes the egg’s outer layer to allow penetration.

7. What Happens Before Birth?
When sperm enter the vagina – they swim through the uterus and fallopian tubes. Fertilization occurs in fallopian tubes

8. Prenatal Development
Prenatal development is the development of the baby during the period before birth.
Before birth, the zygote develops first into an embryo and then into a fetus.
Zygote
Embryo
Fetus

9. Period of the Zygote Super brief
When the fertilized egg divides into 2 cells

10. Period of the Embryo From the 2 cell stage through the 8th week
After zygote divides into two cells, the cells continue to divide as they travel to the uterus.
Embryo is over 100 cells by the time it reaches the uterus.
Ball of cells attaches to the lining of the uterus
Placenta forms around week 4

11. Attaching to wall of the uterus

12. Period of the Fetus From the end of 8 weeks until birth
Internal organs start to develop
The body parts, organs and systems which were formed during the embryo period will become much more developed and begin to function.
During the fetal period the baby may increase in length as much as twelve inches.

13. Protecting and Nourishing the Embryo
Membranes and structures that from in the uterus during pregnancy protect and nourish the developing baby

14. Protecting and Nourishing the Embryo
Membranes and structures that from in the uterus during pregnancy protect and nourish the developing baby
Membranes
Amniotic sac
Placenta
Structures
Umbilical Cord

15. Amniotic Sac Surrounds the embryo and is filled with fluid
Fluid cushions and protects the embryo and fetus

16. Placenta Links the embryo to the mother
Allows substances to be exchanged between bloodstreams

17. Umbilical Cord
Ropelike structure that forms between the embryo and placenta.
Contains blood vessels from embryo that link it to the placenta

18. What Happens During Childbirth?
The birth of a baby takes place in three stages: labor, delivery, & afterbirth

19. Labor 1st stage of birth Contractions of uterus cause cervix to open
May last from 2 – 20+ hours

20. Delivery 2nd stage of birth Head first – hopefully
Can last several minutes – 2 hours
After umbilical cord is cut

21. Afterbirth 3rd and final stage of birth Soon after delivery
Muscles in uterus contract
Pushes placenta and amniotic sac out
Usually lasts less than 1 hour

22. Birth and the Baby
During birth, pressure from contractions causes baby’s O2 supply to decrease.
Baby’s heart rate increases because of the release of adrenaline in endocrine system

23. Multiple Births Twin births are most common multiple birth
Two types of twins
Identical
1 zygote splits into 2 embryos
Fraternal
2 sperm fertilize 2 eggs

24. Timeline of pregnancy conception 1 month pregnant 2 months pregnant

25. What two things are happening during labor?
Questions for review
What is the placenta?
How many eggs and sperm are needed for the development of identical twins?
What two things are happening during labor?

26. More questions… The umbilical cord forms between what 2 “things”?
What is the function of the amniotic sac?
After fertilization occurs, what are the 3 stages of baby development?
When does a zygote become an embryo?

27. Stop here
If interested…more detail of what happens each month is in the following slides.

28. Period of the Embryo First Month
By the end of the first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

29. Embryo -Two Months
The embryo is about 1 inch long and has distinct, slightly webbed fingers. Veins are clearly visible. The heart has divided into right and left chambers.

30. Three Month Fetus
By now the fetus is 2 1/2 to 3 inches long and is fully formed. He has begun swallowing and kicking.
All organs and muscles have formed and are beginning to function.

31. Fetus - Fourth Month
Your baby is covered with a layer of thick, downy hair called lanugo.
His heartbeat can be heard clearly. This is when you may feel your baby's first kick

32. Fetus- 4th Month

33. Fetus Five Months
A protective coating called vernix caseosa begins to form on baby's skin.
By the end of this month, your baby will be nearly 8 inches long and weighs almost a pound

34. Fetus Six Months Eyebrows and eyelids are visible.
Your baby's lungs are filled with amniotic fluid, and he has started breathing motions.
If you talk or sing, he can hear you.

35. Six Month Fetus

36. Fetus Seven Months
By the end of the seventh month, your baby weighs about 3 1/2 pounds and is about 12 inches long.
His body is well-formed.
Fingernails cover his fingertips

37. Fetus Eight Months
Your baby is gaining about half a pound per week, and layers of fat are piling on.
He has probably turned head-down in preparation for birth.
He weighs between 4 and 6 pounds.

38. 8th Month Fetus

39. Fetus Nine Months
Your baby is a hefty 6 to 9 pounds and measures between 19 and 22 inches.
As he becomes more crowded, you may feel him move around less.

40. Lightening
Sometimes during the ninth month, the baby’s weight seems to shift down and the mother feels more comfortable in her upper abdomen.
This is called Lightening
This means the baby has dropped into the birth canal and birth is not far off

41. Weight Gain Baby 7.5 lb Placenta 1.5 lb Uterus 2 lb Amniotic Fluid
Extra Blood & Water Retention
4.5 lb
Breast Tissue
3 lb
Maternal Stores of Protein
4 lb
The recommended weight gain for the average woman during pregnancy is pounds and is distributed as follows: