FETAL%20DEVELOPMENT

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FETAL DEVELOPMENT

• Peggy Pannell RN, MSN

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Learning Goals

• Normal Fetal Development
• From ovulation to birth
• Teratogen
• Definition and potential effects on development

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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

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FERTILIZATION

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

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Stages and Time Frames

• Ovum
• Zygote
• Morula
• Blastocyst
• Embryo
• Fetus
• (Oh, Zee my baby eats fast)

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IMPLANTATION
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PRIMARY GERM LAYERS

• Ectoderm
• Mesoderm
• Endoderm

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GESTATIONAL AGE

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

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GESTATIONAL AGE

• Nageles 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 LNMPDecember 16 2006
• add 7 days Dec. 23 2006
• subtract 3 months Sept 23 2006
• add 1 year Sept 23 2007, estimated due date (EDD)

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TRIMESTERS

• Trimester
• 1st weeks 1-13
• 2nd weeks 14 - 26
• 3rd weeks 27 and on
• (38-40 WEEKS)

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STAGES OF DEVELOPMENT
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FETAL MEMBRANES

• Amnion
• Chorion

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1 Month

• First TrimesterAt 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

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Month 2

• First TrimesterAt 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

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Month 3

• First TrimesterAt 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

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Month 4

• Second TrimesterAt 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

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Month 5

• Second TrimesterAt 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

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Month 6

• Second TrimesterAt 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

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Month 7

• Third TrimesterAt 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

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Month 8

• Third TrimesterAt 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

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Month 9

• Third TrimesterAt 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

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AMNIOTIC FLUID

• Clear, yellowish fluid surrounding the developing
  fetus.
• Average amount 1000 ml.
• Having lt 300ml Oligohydramnios, associated with
  fetal renal abnormalities.
• Having gt 2 L Hydramnios, associated with GI and
  other malformations.

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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

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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 (whartons jelly) to prevent
  kinking and knotting.
• Contains NO pain receptors.

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PLACENTA
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PLACENTA
mom
MOM
Baby
Baby
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PLACENTA

• Produce protein hormones
• Human chorionic gonadotrophin (HCG)- 8-10 days
  past conception, is basis for pregnancy test
• Progesterone
• Estrogen
• Human Placental Lactogen

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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

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PLACENTA

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

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VIABILITY

• Capability of fetus to survive outside uterus at
  the earliest gestational age - 22-24 weeks
• Survival depends on
• Maturity of fetal central nervous system
• Maturity of lungs

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RESPIRATORY SYSTEM

• Terminal SAC period - 24 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 21 (MATURITY)

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CARDIOVASCULAR SYSTEM

• 1st System to function
• FHR 120-160/Min
• Can hear FHR with doppler at 10-12 Weeks

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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.

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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

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• 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 gt2 bones meet
• 7-8 Weeks arms leg movements

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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

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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

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NEUROLOGICAL SYSTEM

• Formed from the ectoderm during the 3rd week
• Respiratory effort 18 1/2 WKS
• Swallowing 12 1/2 WKS
• Sucking 29 WKS
• Fetal movement felt 16-20 WKS
• (Quickening)

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ENDOCRINE 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

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IMMUNE SYSTEM

• Passive immunity - FROM MOM
• Active immunity - FROM FETUS

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MULTIFETAL PREGNANCY

• TWINS
• MULTIFETAL PREGNANCIES

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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

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STAGES OF DEVELOPMENT