Prenatal Development and Birth

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Prenatal Development and Birth

• Chapter 4

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Periods of Prenatal Development

• The Period of the Zygote
• Zygote ? blastocyst
• Cell differentiation
• of blastocysts that fail to implant?

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Periods of Prenatal Development

• The Period of the Zygote (cont)
• Outer layer of blastocyst develops into
• Amnion
• Chorion
• Placenta
• Umbilical cord
• note that these structures actually develop
  during the period of the embryo

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Periods of Prenatal Development

• The Period of the Embryo
• From implantation (week 3) to week 8
• Embryonic disk is already differentiating into
• Ectoderm (nervous system, skin, hair, sensory
  receptors
• Mesoderm (muscles, bones, circulatory system,
  reproductive system, excretory system)
• Endoderm (digestive system, lungs, urinary tract,
  other internal organs)

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Periods of Prenatal Development

• The Period of the Embryo (cont)
• By 4th week, heart has formed and begun to beat
• Becomes more human in appearance during 2nd month
• Sexual differentiation during 7th 8th weeks

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Periods of Prenatal Development

• The Period of the Fetus
• Final 7 months of pregnancy
• Fetus
• Digestive and excretory systems functional
• Sex detected by ultrasound by end of 3rd month
• Kicks and movements strong enough to be felt
• Organ systems mature rapidly during final 3 months

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Periods of Prenatal Development

• The Period of the Fetus (cont)
• Viable between 22-28 weeks
• Receives antibodies
• Assume upside-down position in final weeks
• Weight of head
• Shape of uterus

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Trends in Development

• Cephalocaudal Trend
• Proximodistal Trend

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Teratogens

• Root word means formation of monsters
• Harm isnt always simple or straightforward
• Amount and length of exposure
• Genetic makeup of mother/baby
• Presence of several negative factors

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Teratogens

• Same defect ? different teratogens
• One teratogen ? different defects
• Some effects seen later

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Teratogens

• Age of baby
• Sensitive period

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Teratogens

• Paternal influences often overlooked
• Direct and indirect effects
• Second hand smoke
• Chemicals
• Cocaine can hitchhike
• Smoking, alcohol, drug use ? sperm
• Diets low in vitamin C

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Other Factors

• Exercise
• Nutrition
• Emotional stress
• Rh blood incompatibility
• Maternal/Paternal age
• Older ? less fertile, more risk of disorders
• Younger ? increased risk of prematurity, infant
  death

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Other Factors

• Infectious Diseases
• Prenatal Care
• Previous births

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Perinatal Environment

• Environment surrounding birth
• Stages of childbirth
• Contractions
• Delivery
• Afterbirth
• Newborn appearance

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Perinatal Environment

• Assessing the Newborn
• Apgar scale
• 1 minute and 5 minutes after birth

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Perinatal Environment

• Assessing the Newborn
• Neonatal Behavioral Assessment Scale (NBAS)
• Several days after birth
• 20 inborn reflexes
• Reactions to comforting and social stimuli
• Unresponsiveness may indicate neurological
  problems
• Can be a parent teaching tool

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Perinatal Environment

• Complications
• Anoxia
• Severe ? cerebral palsy, mental retardation
• Mild ? irritability, motor/cognitive delays
• Chances have been reduced with fetal monitoring
• Respiratory distress syndrome
• Complicated delivery
• Forceps
• Cesarean
• Medications

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Preterm and Small-for-Date

• Preterm born more than 3 weeks early, but
  appropriate weight for time in womb
• Small-for-Date underweight due to slow fetal
  growth
• Greater risk than preterm
• Causes include smoking, drug use, stress, lack of
  prenatal care, multiple births, social support
• Postterm born after 42 weeks