Prenatal Development - Slide 1

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					Prenatal Development

      Chapter 2
Biological Beginnings:
 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

 Sperm can live for 6 days and ova for one.
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)
Period of the Zygote

 4th day – blastocyst, hollow, fluid filled
  ball (60-70 cells)
   – Inside, embryonic disk will become
     new organism
   – Outside, troboblast, protective
Period of the Zygote

 Within about 1 week of conception,
 cell differentiation begins

 Implants (attaches to the uterine wall)
 on the 10th to 14th day
Period of the Zygote

 Troboblast will form the amnion (fluid sac
  which regulates temperature and forms a

 Will also form the chorion, from which
  fingerlike villi or blood vessels emerge and
  the placenta forms as they burrow into the
  uterine lining.
Embryonic Period – 3rd week
after conception

 Umbilical cord connects the growing
  organism to the placenta

 It has one vein and two arteries

 The mother’s and embryo’s blood will not
  mix directly (red blood cells, bacteria,
  hormones, maternal waste are filtered)
Embryonic Period – 3rd week
after conception

 Embryonic disk forms:
  – Ectoderm – skin and nervous

  – Mesoderm – muscles, skeleton,
    circulatory system

  – Endoderm – digestive system,
    lungs, urinary tract, glands
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.
  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

– End of 3 months, 3 inches, 3 ounces
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
Period of the Fetus – Growth and
Finishing Phase – 2nd Trimester

  – Mother can feel movements
  – Can hear heartbeat with ordinary

  – Neurogenesis proceeds rapidly
    (250,000 neurons per minute)

  – At 20-weeks can be stimulated/irritated
    by sound; will shield eyes during
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
Problems with Preemies

 – Depends upon gestational age at
 – Breathing
    Hyaline membrane disease
 – Regulating blood oxygen levels
 – Apnea
 – Temperature regulation
 – Feeding
 – Parenting – 40% faster weight gain &
   brain development with touch
    Kangaroo care
Fetal Period – 3rd Trimester
 – Begins sleep-wake pattern
 – Responsiveness, can feel pain
   after 24 weeks
 – React to sounds
 – Prefer mother’s voice
 – Adds fat (5 pounds)
 – Receives antibodies
 – Assumes birth position (head
   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)
 Teratogens - Drugs

 Examples
 – Thalidomide – 7000 infants affected
    Limbs, heart, ears, kidneys, genitals

 – DES (diethylstilbestrol) – reproductive
   problems in adult children (cancer;
   abnormalities in reproductive organs)
 Teratogens - Drugs

  – Don’t 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
 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
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.
  Teratogens - Alcohol

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

 Radiation (Hiroshima, Nagasaki,
  – 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
Teratogens –
Infectious diseases


Genital herpes

Other Maternal Factors


Emotional stress

Maternal age & previous
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.
 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)?
The Birth Process
– Dilation and effacement (of the
  At  transition a clear channel
    from the uterus to the vagina is
    formed (birth canal)
– Birth of the baby (Delivery) 20-50
– Delivery of the placenta (afterbirth)
  (5-10 minutes)
Birth Complications and
Medical Interventions
– Anoxia
– Breech position
– Cerebral palsy
– Fetal monitors
– Medication (90-95% of births)
  Analgesics,   anesthetics
– Cesarean delivery (30% of births)
Low Birthweight Infants (LBW)

 (Low)Birthweight   is the best available
  predictor of infant survival & healthy

 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
    Low Birthweight Infants (LBW)
    –Preterm babies – born early
     (35 or fewer weeks) may be
     weight appropriate

    –Small-for-date babies have
     more serious problems.
Apgar (1 & 5 minutes after
 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
The Newborn - Arousal

 Sleep 18-20 hours per day

 50% is REM sleep

 SIDS (Sudden Infant Death

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