Prenatal Development

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Prenatal Development
Prepared by Dr. Hoda Abed El Azim
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Objectives

• List the three stages of prenatal development.
• Discus the two principles of prenatal
  development.
• State the characterized of each prenatal
  development stage.
• Explain why defects and miscarriages most often
  occur during embryonic stage.
• Describe several developmental changes that occur
  during each month of pregnancy.
• Discus environmental influences can affects
  prenatal development.
• Identify techniques can assess a fetuss health.

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Gestation)) Stages of prenatal development

• Germinal
• Embryonic
• Fetal
• During these three stages of gestation the
  original single celled zygote grows into an
  embryo and then a fetus.
• Growth and motor development occur from top to
  bottom and from the center of the body outward.

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• Development proceeds from the head to the lower
  part of the trunk.

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Developmental Principles

• 1. Cephalocaudal Principle
• Development proceeds from the head to the lower
  part of the trunk.
• An embryos head, brain, eyes develop earliest
  and are disproportionately large until the other
  parts catch up.
• At 2 months of gestation, the embryos head is
  half the length of the body.
• By the time of birth, the head is only one fourth
  the length of the body.

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• 2. Proximodistal principle
• Development proceeds from parts near the center
  of the body to outer ones.
• The embryos head and trunk develop
• before the limbs, and the arms and legs
• before the fingers and toes.

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1. Germinal Stage

• From fertilization to 2 weeks of gestational age.
  
• Within 36 hours after fertilization, the zygote
  enters a period of rapid cell division and
  duplication (mitosis).
• 3-4 days zygote down to the uterus, form a
  blastocyst which floats freely in the uterus for
  a day or two and then begins to implant itself in
  the uterine wall.

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Germinal Stage cont.

• 10-20 of blastocyst become embryos mass, this
  mass will differentiate into three layers.
• Ectoderm will become (layer of skin, nails,
  hair, teeth, sensory organs, and nervous system).
• Endoderm will become (digestive system, liver,
  pancreas, salivary glands and respiratory
  system).
• Mesoderm will develop and form inner layer of
  skin, muscles, skeleton and excretory and
  circulatory systems.

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Germinal Stage cont.

• Other parts of blastocyst begin to develop into
  organs that will nurture and protect embryo.
• Amniotic cavity or amniotic sac.
• Placenta
• Umbilical cord
• Nutrients from the mother pass from her blood to
  the embryo blood vessels, via umbilical cord.
• Embryonic blood vessels in the umbilical cord
  carry embryonic wastes to the placenta, where
  they can be eliminated by maternal blood vessels.

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Embryonic Stage (2 to 8 weeks)

• Characterized by rapid growth and development of
  major body systems and organs.
• This is a critical period when the embryo is most
  vulnerable to destructive influences in the
  prenatal environment.

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Fetal Stage (8 weeks to birth)

• During this period,
• The fetus grows rapidly to about 20 times its
  previous length, and organs and body systems
  become more complex.

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First month

• Growth is more rapid
• The embryo size 10.000 times greater than the
  zygote.
• Length ½ inch.
• Small heart beats (65 times a minute).
• Very small veins and arteries.
• The sex cannot be detected.

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Second Month

• The fetus is less than 1 inch in long.
• Weighs only 9 gm.
• The head is half its total body length.
• Facial part are clearly developed.
• The arms have (hands, fingers) and the legs have
  (knees, ankles and toes).
• The fetus has a thin covering of skin.
• Bain impulses coordinate the function
• of the organ system.
• Sex organs are developing.
• The heart beat is steady.

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Third Month

• Length 3 inches.
• Weight 28 gm.
• The head one third its total length.
• Sex can easily be detected.
• The organs systems are functioning.
• (breath, swallow amniotic fluid into the lung
• and expel it , urinate).
• Movement and reflexes activities.

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Fourth Month

• The head one fourth of the total body length.
• Measures 8-10 inches.
• Weight about 170 gm.
• The umbilical cord is as long as the fetus
• and will continue to grow with it.
• The placenta is fully developed.
• Quickening.
• Reflexes activity become brisker due to increase
  muscular development.

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5 Month

• Weighing about 1 pound (454 gm).
• Measuring about 12 inches.
• Signs of individual personality appears.
• Sleep Wake patterns.
• Position in the uterus (lie).
• Stretching, squirming.
• The sweat and sebaceous glands are functioning.
• Eyebrows, eyelashes, fine hair on the head, and
  lanugo hair.

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6 Month

• 14 inches long.
• Weights 1 ¼ pounds.
• Has fat pads under the skin.
• The eye are complete, closing, opening,
• and looking in all directions.
• It can her.

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Seventh Month

• About 16 inches long and weighing 3 to 5 pounds.
• Fully developed reflex patterns.
• Cries, breathes, and swallows and it may be suck
  its thumb.
• The lanugo may disappear.
• Continue grow head hair.

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8 Month

• 18-20 inches long.
• Weight 5-7 pounds.
• A layer of fat is developing over
• the foetus's entire body.
• Movement are curtailed or imperfect.

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9 Month

• About week before birth the fetus stop growing.
• Reached an average weight of about 7 ½ pounds
  and length of about 20 inches, with boys little
  longer and heavier than girls.
• The organ systems are operating more efficiently.
  
• The heart rate increases.
• More wastes are expelled through
• the umbilical cord.

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New born
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Environmental influences (Maternal Factors)

• 1. Nutrition and maternal weight.
• 2. Physical activity and strenuous work.
• Regular exercise prevents constipation and
  improve respiration, circulation, muscles tone,
  and comfortable pregnancy, safer delivery.
• Strenuous working may be associated with
  premature birth.

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• 3. Drug Intake
• Nearly thirty drugs have been found to be
  teratogenic in clinically recommended doses.
• ( antibiotic, several hormones, certain
  anticancer, and aspirin and other non steroidal
  anti- inflammatory drugs.
• No medication be prescribed for a pregnant or
  breast feeding woman unless it is essential for
  her health or her childs.

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• 4. Alcohol drinking even small amount may harm a
  fetus.
• Moderate to heavy drinking during pregnancy
  disturb an infants neurological and behavioural
  functioning.
• 5. Smoking
• Women who smoke during pregnancy have low birth
  weight babies.
• 6. HIV / AIDS
• The virus transmitted through the placenta to the
  fetuss bloodstream.
• After birth the virus can be transmitted through
  breast milk.

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• 7. Other Maternal Illnesses
• Rubella leads to deafness and heart defects in
  baby.
• Diabetes
• Toxoplasmosis infection.
• 8. Maternal stress.
• 9. Maternal age.
• 10. Outside environmental hazards.
• Air pollution.
• Chemicals.
• Radiation.
• Extremes of heat and humidity.

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Monitoring Prenatal Development

• What techniques can assess a fetuss health and
  why is prenatal care important?
• Ultrasound (sonogram).
• Fetoscopy
• Amniocentesis
• Chorionic villus sampling.
• Umbilical cord sampling
• Maternal blood test

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• Thank You