Prenatal Development

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Prenatal Development

• Chapter 2

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Biological BeginningsConception

• Ova are released from the ovaries and travel down
  the fallopian tubes, where conception occurs.
  Development begins at conception.
• Males produce an average of 300 million sperm per
  day. Only 300-500 reach the ovum.
• Sperm can live for 6 days and ova for one.

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The Three Periods of Pregnancy

• Germinal (Period of the Zygote)
• First two weeks, ends with implantation
• Embryonic Period
• 2-8 weeks, organogenesis
• Fetal Period
• 9 weeks birth (all trimesters)

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Period of the Zygote (Germinal)

• 4th day blastocyst, hollow, fluid filled ball
  (60-70 cells)
• Inside, embryonic disk will become new organism
• Outside, troboblast, protective covering

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Period of the Zygote (Germinal)

• Within about 1 week of conception, cell
  differentiation begins
• Implants (attaches to the uterine wall) on the
  10th to 14th day

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Period of the Zygote (Germinal)

• Troboblast will form the amnion (fluid sac which
  regulates temperature and forms a cushion)
• Will also form the chorion, from which fingerlike
  villi or blood vessels emerge and the placenta
  forms as they burrow into the uterine lining.

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Embryonic Period 3rd week after conception

• Umbilical cord connects the growing organism to
  the placenta
• It has one vein and two arteries
• The mothers and embryos blood will not mix
  directly (red blood cells, bacteria, hormones,
  maternal waste are filtered)

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Embryonic Period 3rd week after conception

• Embryonic disk forms
• Ectoderm skin and nervous system
• Mesoderm muscles, skeleton, circulatory system
• Endoderm digestive system, lungs, urinary
  tract, glands

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Embryonic Period (2-8 weeks) - Organogenesis

• Neural tube develops first, will become brain and
  spinal cord
• Next, heart begins to pump blood
• The basic structure of all the organ systems
  grows
• Eyes, ears, nose, jaw, neck, arms legs, fingers
  toes form
• At the end of this period, it weighs less than
  one ounce, about one inch long.

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Period of the Fetus Growth and Finishing Phase
3rd Month

• The fetus can kick, bend its arms, form a fist,
  curl its toes, open its mouth, suck its thumb,
  smile swallow
• By 12th week external genitals well formed, also
  fingernails, toenails, tooth buds, eyelids
• Heartbeat can be heard with a special stethoscope
• End of 3 months, 3 inches, 3 ounces

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Period of the Fetus Growth and Finishing Phase

• Called a fetus from the 8th week until birth
• Fetus means fully-formed human being because all
  organ systems are now in place
• During the 3rd month (12-16 weeks) it will have
  coordinated movements, be able to roll over in
  the amniotic fluid
• Hair, eyelashes, eyebrows will grow

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Period of the Fetus Growth and Finishing Phase
2nd Trimester

• Mother can feel movements
• Can hear heartbeat with ordinary stethoscope
• Neurogenesis proceeds rapidly (250,000 neurons
  per minute)
• At 20-weeks can be stimulated/irritated by sound
  will shield eyes during fetoscopy

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Period of the Fetus Growth and Finishing
Phase-Age of Viability

• Age at which the fetus can survive outside the
  mother (38-40 weeks is full term)
• 5 survive at 22 weeks
• 50 survive at 26 weeks (6 months)
• 95 survive at 28 weeks

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Problems with Preemies

• Depends upon gestational age at birth
• Breathing
• Hyaline membrane disease
• Regulating blood oxygen levels
• Apnea
• Temperature regulation
• Feeding
• Parenting 40 faster weight gain brain
  development with touch
• Kangaroo care

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Fetal Period 3rd Trimester

• Begins sleep-wake pattern
• Responsiveness, can feel pain after 24 weeks
• React to sounds
• Prefer mothers voice
• Adds fat (5 pounds)
• Receives antibodies
• Assumes birth position (head down)

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Teratogens (Monsters)

• Any environmental agent that causes prenatal
  damage (leading to birth defects)
• Types drugs, diseases, radiation, environmental
  pollutants
• Factors dose, resilience (heredity), number of
  teratogens, gestational age at exposure
  (embryonic period worst)

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Teratogens - Drugs

• Examples
• Thalidomide 7000 infants affected
• Limbs, heart, ears, kidneys, genitals
• DES (diethylstilbestrol) reproductive problems
  in adult children (cancer abnormalities in
  reproductive organs)

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Teratogens - Drugs

• Dont take anything without consulting your
  obstetrician
• Examples
• Aspirin may be associated with LBW, infant
  death, lower IQ, poor motor development
• Caffeine LBW, miscarriage, irritable infants

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Teratogens Illegal Drugs

• Cocaine
• Heroin/methodone
• Prematurity, LBW, breathing difficulties,
  physical defects, infant death, stressed and drug
  addicted
• Marijuana
• Smaller head size, disturbed sleep, inattention
  in infancy

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Teratogens - tobacco

• Nicotine constricts blood vessels and lessens
  blood flow to the uterus, causes the placenta to
  grow abnormally, reduces the transfer of
  nutrients, raises the carbon monoxide
  concentration in the blood stream which may
  damage the central nervous system
• Smoking during pregnancy is associated with LBW
  and increased frequency of prematurity, impaired
  breathing during sleep, infant death and
  childhood cancer.

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Teratogens - Alcohol

• Fetal Alcohol Syndrome (FAS/FAE) is the leading
  preventable cause of mental retardation.
• Other symptoms include impaired motor
  coordination, attention, memory language slow
  physical growth overactivity.
• Facial abnormalities include widely spaced eyes,
  short eyelid openings, thin upper lip, small
  head, small upturned nose.

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Teratogens - Alcohol

• Lesson Women should avoid alcohol during
  pregnancy.
• Alcohol inteferes with brain development
  causing abnormalities in structure and function.
• Oxygen needed for cell growth is taken from the
  fetus to metabolize alcohol.

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Environmental Teratogens

• Radiation (Hiroshima, Nagasaki, Chernobyl)
• Miscarriages, babies with underdeveloped brains,
  physical deformities, slow growth
• Mercury 1950s Minamata, Japan resulting brain
  damage in children
• Lead prematurity, LBW, brain damage, physical
  defects
• PCBs (insulators for electrical equipment)
  lower intelligence

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Teratogens Infectious diseases

• Rubella
• HIV/AIDS
• Genital herpes
• toxoplasmosis

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Other Maternal Factors

• Nutrition
• Emotional stress
• Maternal age previous births

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Prenatal Health Care

• 18 of women in the U.S. wait until the second
  trimester, and 4 until the end to get care
• Many of these are unmarried, adolescent, or
  poverty stricken.
• Reasons include lack of insurance, ambivalent
  feelings, high risk behaviors, and lack of
  transportation.

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Approaches to Childbirth

• How much medical care/availability?
• Should it be natural or prepared?
• How about the epidural?
• How about a midwife (or a doula)?

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The Birth Process

• Dilation and effacement (of the cervix)(Labor)
• At transition a clear channel from the uterus to
  the vagina is formed (birth canal)
• Birth of the baby (Delivery) 20-50 minutes
• Delivery of the placenta (afterbirth) (5-10
  minutes)

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Birth Complications and Medical Interventions

• Anoxia
• Breech position
• Cerebral palsy
• Fetal monitors
• Medication (90-95 of births)
• Analgesics, anesthetics
• Cesarean delivery (30 of births)

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Low Birthweight Infants (LBW)

• (Low)Birthweight is the best available predictor
  of infant survival healthy development.
• Low Birthweight Babies weigh less than 5.5
  pounds.
• 1 of 14 American infants
• More problems with inattention, overactivity,
  language delays, low IQ scores, and motor
  deficits

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Low Birthweight Infants (LBW)

• Preterm babies born early (35 or fewer weeks)
  may be weight appropriate
• Small-for-date babies have more serious problems.
  

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Apgar (1 5 minutes after birth)

• 5 characteristics
• Heart rate, respiratory effort, reflex
  irritability, muscle tone, color)
• 0,1,or 2 points on each
• Total score
• 7, good physical condition
• 4-6, baby requires assistance
• 3-, infant in serious danger, requires emergency
  attention

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The Newborn - Arousal

• Sleep 18-20 hours per day
• 50 is REM sleep
• SIDS (Sudden Infant Death Syndrome)