Conception and Development of the Embryo and Fetus

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Chapter 7

• Conception and Development of the Embryo and
  Fetus
• http//www.youtube.com/watch_popup?vfKyljukBE70

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Implantation

• Zygote (cell that results from fertilization)
  propelled by
• Cilia
• Peristalsis
• Reaches uterine cavity in 3 to 4 days

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Nidation

• Occurs by 10th day after fertilization
• Implantation bleeding
• Blastocyst (5 days after fertilization) is buried
  beneath the endometrial surface

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Placenta

• Develops from trophoblast cells
• Provides oxygenation, nutrition, waste
  elimination, and hormones
• Protects fetus

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Placental Hormones

• Human chorionic gonadotrophin (hCG)
• Human placental lactogen (hPL)
• Progesterone
• Estrogen

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Progesterone

• A female hormone (ovaries) during the release of
  the mature egg from an ovary
• Helps prepare the lining of the uterus to receive
  the fertilized egg
• Produced by the placenta during pregnancy
• What happens if fertilization does not occur?

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Estrogen

• For growth and development of female sexual
  characteristics and reproduction
• Produced by the ovaries and the placenta
• Prompts hyperplasia and hypertrophy (growth in
  the number of cells and size during pregnancy)
• Breast tissue enlarges, uterus to expand, uterine
  contractility to prepare for labor

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• placenta

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Umbilical Cord

• Usual locationcenter of placenta
• 55 cm long (21 in) 1 to 2 cm diameter
• Vessels one vein, two arteries
• Whartons Jelly protects umbilical cord from
  compression

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Fetal Circulation

• Heart begins to beat and circulate blood by end
  of third week
• Umbilical vein blood from placenta to fetus
• http//tube.medchrome.com/2011/04/fetal-circulatio
  n-explained-with-video.html

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Fetal Circulation

• Three unique shunts
• Ductus venosus bypasses liver and enters
  inferior vena cava
• Foramen ovale right and left atria to supply
  blood to head, and upper and lower extremities
• Ductus arteriosus returning blood bypasses lungs

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Fetal Circulation
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Fetal Membranes and Amniotic Fluid

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Embryonic Membranes

• Early protective structures
• Two separate membranes
• Amnioninner membrane, contains amniotic fluid
• Chorionouter membrane, forms fetal portion of
  placenta
• Slightly adherent, form amniotic sac

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Why is amniotic fluid index important in
determining fetal well being?
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Purposes of Amniotic Fluid

• Protects and cushions fetus
• Maintains normal body temperature
• Symmetrical fetal growth
• Freedom of movement
• Essential for normal fetal lung development

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Amniotic Fluid

• Fetal urine and lung secretions primary
  contributors
• Slightly alkaline
• Contains antibacterial, other protective
  substances

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Threats to Embryonic and Fetal Development

• Chromosomes and teratogens
• Medications and other substances
• Vitamins, alcohol, tobacco, caffeine, drugs,
  radiation, and lead
• TORCH infections

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Nurses Role in Prenatal Evaluation

• Initial prenatal visit
• Assessment
• cultural, emotional, physical, and physiological
  factors
• Education
• Teratogen exposures
• Genetic disorders
• Prenatal tests

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Maternal Age and Chromosomes

• Age 35 and above
• Increased risk of chromosomal abnormalities
• Down syndrome (trisomy 21)

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Trisomy 18
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Minimizing Threats to Embryo/Fetus

• Nurses role
• Assessment
• Environmental and lifestyle risks
• Knowledge
• Physical and psychosocial well-being
• Preconception counseling