1. Reproduction: A Brief Review

2. Conception and Fertilization
Conception is the fertilization of the female ovum by the male sperm
Fertilization occurs when a sperm enters the ovum and their nuclei unite. Usually occurs in the outer third of the fallopian tube. Takes 3 days for the zygote to reach the uterine cavity
Implantation occurs when the embryo buries itself in the upper segment of the uterine lining
Pregnancy also referred to as gestation and lasts approximately 280 days (40 weeks)

3. Three Periods of Fetal Development
Pre-embryonic Period: fertilization through the first two weeks. Period of the zygote
Embryonic Period: third through eighth week. Highly vulnerable to teratogens, viruses, drugs, radiation, or infections. End of 8th week, all organ systems and external structures are formed and unmistakably human
Fetal Period: eighth week through the fortieth week or birth. Viability now possible at weeks after conception.

4. Placental Hormones
1) Human Chorionic Gonadotropin (hCG): Stimulates corpus luteum to produce progesterone and estrogen until the placenta assumes that function
2) Estrogen: Produced by the ovaries during menstrual cycle. Placenta assumes production after the 6th or 7th week. Increases vascularity in the pregnant woman
3) Progesterone: Produced by the corpus luteum and then the placenta. Most important pregnancy hormone as it maintains the endometrium and prevents abortion. Relaxes smooth muscle in the pregnant woman

5. Placental Hormones
4) Human Placental Lactogen (hPL): Increases availability of glucose for the fetus. Glucose required for fetal growth and development. Levels increase steadily during pregnancy
5) Relaxin: Inhibits uterine activity, softens connective tissue, relaxes pelvic joints to facilitate birth

6. Fetal Development Placenta Means of metabolic exchange
Filters some harmful substances from reaching fetus
Covers about half uterine surface
Function depends on maternal blood pressure

7. Placenta
Fetal Side
Maternal Side
(attached to uterine wall)

8. Functions of the Placenta
Endocrine Functions
Produces:
Human Chorionic Gonadotropin (hCG)
Ensures estrogen and progesterone secretion
Human Placental Lactogen (hPL)
Facilitates glucose transport across placenta

9. Functions of the Placenta
Endocrine Functions
Progesterone
Maintains endometrium
Decreases contractility of uterus
Estrogen
Stimulates uterine growth
Stimulates uteroplacental blood flow
Stimulates myometrial contractility

10. Functions of the Placenta
Metabolic Functions
Respiration
Oxygen and CO2 diffuse between the placental membrane from maternal blood to fetal blood
Nutrition
Water, electrolytes, carbohydrates, fat, protein, and vitamins pass across placental membrane

11. Functions of the Placenta
Excretion
Metabolic waste products cross the placental membrane from the fetal blood into maternal blood
Maternal kidneys excrete the wastes
Storage
Carbohydrate, proteins, calcium, and iron are stored in the placenta for ready access to meet fetal needs

12. Placenta
Viruses, drugs caffeine, alcohol, nicotine, carbon monoxide and other toxic substances can cross the placental membrane
Bacteria and protozoa infect placenta first, then fetus

13. Membranes Chorion Outermost membrane, closest to uterine lining
Contains the major umbilical blood vessels
Chorionic villi infiltrate maternal tissues and become the fetal side of the placenta

14. Membranes Amnion Inner membrane
Embryo draws amnion around itself forming a fluid filled sac
Later adheres to the chorion to make one membrane
Produces amniotic fluid
*Chorioamnionitis: refers to the infection of both of these membranes

15. Fetal Circulation

16. Amniotic Fluid
Full term: should have approximately ,000 mL fluid
Oligohydramnios: insufficient amniotic fluid; less than 300 mL. Can be related to problem with fetal renal development
Polyhydramnios/Hydramnios: Too much amniotic fluid; more than 2,000 mL. Can be related to problem with fetal GI development

17. Components of Amniotic Fluid
Albumin
Urea
Uric acid
Creatinine
Lechithin*
Sphingomyelin*
Phosphatidylgycerol (PG)*
*Determines fetal lung maturity
*L/S ratio of 2:1 confirms fetal lung maturity
Bilirubin
Fat
Fructose
Leukocytes
Proteins
Enzymes
Lanugo hairs

18. Functions of Amniotic Fluid
Cushions fetus; umbilical cord
Allows freedom of movement for musculo-skeletal development
Keeps baby from tangling with membranes
Helps maintain body temperature
Source of oral fluid and waste repository

19. Umbilical Cord 30-90 cm in length 2 cm in diameter
Two arteries: carries deoxygenated blood from fetus to placenta
One vein: carries oxygenated blood from placenta to fetus
Wharton’s Jelly: prevents compression of the blood vessels
**Remember “AVA”: 2 arteries; 1 vein

20. Umbilical Cord

21. Umbilical Cord Vessels

22. How Fetus Obtains Sufficient Oxygen from Maternal Blood
Fetal hemoglobin carries 20-30% more O2 than maternal hemoglobin
Fetal hemoglobin concentration is about 50% more than maternal
Fetal heart rate is about BPM, therefore fetal cardiac output greater than adults
Remember…maternal and fetal blood should not mix. Mixing only occurs at time of delivery when placenta detaches. Only gases, nutrients, wastes… should pass through placental membrane

23. Respiratory System
Maturity coincides with establishment of surfactants during gestational week 35
Lecithin and sphingomyelin-L/S ratio measured to determine maturity
L/S ratio of 2:1 indicates fetal lung maturity

24. Reproductive System
Male and female genitalia indistinguishable until after 9th week
By week 16, ultrasound can confirm sex
At birth, ovaries contain lifetime supply of ova

25. Embryo at 1 Month

26. Implantation

27. 2nd Month Limbs begin to form and a tiny heart begins to beat

28. 3rd Month Embryo now becomes a fetus. Tiny arms and legs can now bend.

29. 4th Month Sex is now evident. Lanugo covers the entire body
4th Month Sex is now evident. Lanugo covers the entire body. The ball is the yolk sac which will produce blood until the fetus can make its own

30. 4th Month Fetus can now hear
4th Month Fetus can now hear. 4-6 ounces of amniotic fluid surrounds the fetus. Size is 5 inches long; weight is 4 ounces

31. 4th Month The legs, with their bones seen through translucent skin, are in motion, even though the mother can’t feel the movement

32. 5th Month Meconium is forming. Brown fat begins to form also
5th Month Meconium is forming. Brown fat begins to form also. Vernix caseosa production is complete.

33. 6th Month Bones begin to harden. Lungs begin to breathe on their own
6th Month Bones begin to harden. Lungs begin to breathe on their own. Fetus is about 10 inches long.

34. 7th Month The eyes start to open and reacts to changes in light
7th Month The eyes start to open and reacts to changes in light. Gets into typical fetal position. Wt. is 3 lbs; 11 inches long.

35. 8th Month Continues to grow rapidly. The testes have descended fully
8th Month Continues to grow rapidly. The testes have descended fully. Nails grow pass the fingertips

36. Full-term perfection!

37. Videos
These five videos take a 3D animated look at pregnancy from week 1 to week 37
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