1. FETAL DEVELOPMENT
Peggy Pannell RN, MSN

2. Learning Goals Normal Fetal Development Teratogen
From ovulation to birth
Teratogen
Definition and potential effects on development

3. Vocabulary Blastocyst Conception Ductus arteriosus Embryo
Fertilization
Fetus
Foramen Ovale
HCG
Implantation
L/S ration
Gestational age
Vernix
Zygote
Placenta
Quickening
Surfactant
Teratogens
Umbilical Cord

4. FERTILIZATION
Begins with 46 pair of chromosomes, splits off to 23 then combine for a unique new 46 pair.

5. Stages and Time Frames Ovum Zygote Morula Blastocyst Embryo Fetus
(Oh, Zee my baby eats fast)

6. IMPLANTATION First weeks of human development:
Blastocyst embedded in endometrium.

7. PRIMARY GERM LAYERS
Ectoderm
Mesoderm
Endoderm

8. GESTATIONAL AGE Fertilization LMP Days 266 280 Weeks 38 40
Gestational age=Time since last menstrual period (LMP)
EDC, EDD, EDB
266 Days after fertilization
280 Days after onset of LMP
Fertilization LMP
Days
Weeks
Calendar Months 8 3/4 9
Lunar Months 9 1/2 10

9. GESTATIONAL AGE Nagele’s Rule
Add 7 days to the first day of the last normal menstrual period, subtract 3 months and add 1 year.
Example:
1st day of LNMP=December
add 7 days = Dec
subtract 3 months = Sept
add 1 year =Sept , estimated due date (EDD)

10. TRIMESTERS Trimester 1st = week’s 1-13 2nd = week’s 14 - 26
3rd = week’s 27 and on
(38-40 WEEKS)

11. STAGES OF DEVELOPMENT

12. FETAL MEMBRANES Amnion Chorion Membranes: Decidua basalis
Decidua capsularis
Decidua basalis
Developing placenta
Yolk sac
Amniotic cavity
Intrauterine cavity
Decidua vera
Mucus plug (operculum)
Chorion (blends with placenta)
Amnion (blends with umbilical cord)
Membranes:
Umbilical cord (funis)
Villi of fetal portion of placenta filled with fetal blood
Lacunae in decidua basalis filled with maternal blood
Amnion
Chorion

13. 1 Month First Trimester At the end of four weeks:
Baby is 1/4 inch in length
Heart, digestive system, backbone and spinal cord begin to form
Placenta (sometimes called "afterbirth") begins to develop
The single fertilized egg is now 10,000 times larger than size at conception

14. Month 2 First Trimester At the end of 8 weeks:
Baby is 1-1/8 inches long
Heart is functioning
Eyes, nose, lips, tongue, ears and teeth are forming
Penis begins to appear in boys
Baby is moving, although the mother can not yet feel movement

15. Month 3 First Trimester At the end of 12 weeks:
Baby is 2 1/2 to 3 inches long
Weight is about 1/2 to 1 ounce
Baby develops recognizable form. Nails start to develop and earlobes are formed
Arms, hands, fingers, legs, feet and toes are fully formed
Eyes are almost fully developed
Baby has developed most of his/her organs and tissues
Baby's heart rate can be heard at 10 weeks with a special instrument called a Doppler

16. Month 4 Second Trimester At the end of 4 months:
Baby is 6 1/2 to 7 inches long
Weight is about 6 to 7 ounces
Baby is developing reflexes, such as sucking and swallowing and may begin sucking his/her thumb
Tooth buds are developing
Sweat glands are forming on palms and soles
Fingers and toes are well defined
Sex is identifiable
Skin is bright pink, transparent and covered with soft, downy hair
Although recognizably human in appearance, the baby would not be able to survive outside the mother's body

17. Month 5 Second Trimester At the end of 5 months:
Baby is 8 to 10 inches long
Weight is about 1 pound
Hair begins to grow on baby's head
Soft woolly hair called lanugo will cover its body. Some may remain until a week after birth, when it is shed.
Mother begins to feel fetal movement
Internal organs are maturing
Eyebrows, eyelids and eyelashes appear

18. Month 6 Second Trimester At the end of 6 months:
Baby is 11 to 14 inches long
Weight is about 1 3/4 to 2 pounds
Eyelids begin to part and eyes open sometimes for short periods of time
Skin is covered with protective coating called vernix
Baby is able to hiccup

19. Month 7 Third Trimester At the end of 7 months:
Baby is 14 to 16 inches long
Weight is about 2 1/2 to 3 1/2 pounds
Taste buds have developed
Fat layers are forming
Organs are maturing
Skin is still wrinkled and red
If born at this time, baby will be considered a premature baby and require special care

20. Month 8 Third Trimester At the end of 8 months:
Baby is 16 1/2 to 18 inches long
Weight is about 4 to 6 pounds
Overall growth is rapid this month
Tremendous brain growth occurs at this time
Most body organs are now developed with the exception of the lungs
Movements or "kicks" are strong enough to be visible from the outside
Kidneys are mature
Skin is less wrinkled
Fingernails now extend beyond fingertips

21. Month 9 Third Trimester At the end of 9 months:
Baby is 19 to 20 inches long
Weight is about 7 to 7 1/2 pounds
The lungs are mature
Baby is now fully developed and can survive outside the mother's body
Skin is pink and smooth
Baby settles down lower in the abdomen in preparation for birth and may seem less active

22. AMNIOTIC FLUID
Clear, yellowish fluid surrounding the developing fetus.
Average amount 1000 ml.
Having < 300ml – Oligohydramnios, associated with fetal renal abnormalities.
Having > 2 L – Hydramnios, associated with GI and other malformations.

23. AMNIOTIC FLUID Protects Fetus Controls Temperature
Supports Symmetrical Growth
Prevents Adherence to amnion
Allows Movement
Source of oral fluid
Acts as a excretion-collection repository

24. UMBILICAL CORD Connecting link between fetus and placenta.
Transports oxygen and nutrients to fetus from the placenta and returns waste products from the fetus to the placenta.
Contains: 2 arteries and 1 vein supported by mucoid material (wharton’s jelly) to prevent kinking and knotting.
Contains NO pain receptors.

25. PLACENTA

26. PLACENTA MOM Baby Baby mom
Schematic drawing of placenta: how it supplies oxygen and nutrition to embryo and removes waste products. Deoxygenated blood leaves fetus through the umbilical arteries and enters placenta, where it is oxygenated. Oxygenated blood leaves placenta through the umbilical vein, which enters the fetus via the umbilical cord
mom
MOM
Baby
Baby

27. PLACENTA Produce protein hormones:
Human chorionic gonadotrophin (HCG) days past conception, is basis for pregnancy test
Progesterone
Estrogen
Human Placental Lactogen

28. PLACENTA
Sieve/filter – allows smaller particles through and holds back larger molecules. Passage of materials in either direction is effected by:
Diffusion: gases, water, electrolytes
Facilitated transfer: glucose, amino acids, minerals.
Pinocytosis: movement of minute particle

29. PLACENTA
Mother transmits immunoglobulin G (IgG) to fetus providing limited passive immunity.
Leakage: caused by membrane defect: may allow maternal and fetal blood mixing.

30. VIABILITY
Capability of fetus to survive outside uterus at the earliest gestational age weeks
Survival depends on:
Maturity of fetal central nervous system
Maturity of lungs

31. RESPIRATORY SYSTEM 30-32 Weeks 1.2 : 1 35 Weeks 2:1 (MATURITY)
Terminal SAC period Weeks to birth
Growth of primitive alveoli
Pulmonary surfactants produced which act as wetting agents that prevent alveolar walls from sticking
Insufficient surfactant - RDS
Lecithin/Sphingomyelin-Phospho Lipids
L/S Ratio
30-32 Weeks 1.2 : 1
35 Weeks 2:1 (MATURITY)

32. CARDIOVASCULAR SYSTEM
1st System to function
FHR /Min
Can hear FHR with doppler at Weeks

33. FETAL CIRCULATION
Arteries in umbilical cord and fetal body carry deoxygenated blood.
Vein in cord and those in fetal body carry oxygenated blood
Ductus venosus connects umbilical vein and inferior vena cava; bypassing portal circulation.

34. FETAL CIRCULATION
Foramen Ovale allows blood to flow from right to left atrium, bypassing lungs.
Ductus Arteriosus allows blood flow from pulmonary artery to aorta, bypassing fetal lungs;

35. HEPATIC SYSTEM
Liver functions 4-6 weeks
Full liver function after delivery
MUSCULO-SKELETAL SYSTEM
Bones and muscles develop by 4th week
Fontanels – areas where >2 bones meet
7-8 Weeks arms & leg movements

36. GASTROINTESTINAL SYSTEM
Forms during 4th week
Middle portion of the intestine projects out into cord during 5th week. Returns during 10th week. If this does not occur- Omphalocele present at birth
Meconium – Dark green to black tarry waste accumulated in the fetal intestine near term

37. RENAL SYSTEM
Kidneys form in 5th week and begin to function 4 weeks later.
Voiding into amniotic fluid
Low volume can show renal dysfunction
Renal malformation can be diagnosed in utero.
GFR is low at birth

38. NEUROLOGICAL SYSTEM Formed from the ectoderm during the 3rd week
Respiratory effort 18 1/2 WKS
Swallowing /2 WKS
Sucking WKS
Fetal movement felt WKS
(Quickening)

39. ENDOCRINE SYSTEM INTEGUMENTARY SYSTEM Thyroid gland 1st to develop
Insulin produced at 20 weeks
INTEGUMENTARY SYSTEM
7th week – Two layers of cells
Vernix caseosa –Protects skin
Lanugo – Fine hair
10th week – Fingernails, toenails

40. IMMUNE SYSTEM
Passive immunity - FROM MOM
Active immunity - FROM FETUS

41. MULTIFETAL PREGNANCY
TWINS
MULTIFETAL PREGNANCIES

42. Teratogens
Environmental exposures that can adversely effect the developing fetus
Maternal Conditions
Alcoholism, Diabetes, Endocrinopathies, Phenylketonuria (PKU), Smoking, Nutritional problems
Infections Agents
Rubella, Toxoplasmosis, Syphillis, Herpes Simplex, Cytomegalic Inclusion Disease, Varicella, Venezuelan Equine Encephalitis
Mechanical Problems (deformations)
Amniotic band constrictions, Umbilical Cord constraint, Disparity in uterine size and uterine contents
Chemicals, drugs, radiation, hyperthermia

43. STAGES OF DEVELOPMENT