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Stages of Fetal Developmentconception.jpg

1. Conception

2. Embryonic Development

3. Fetal Development

Click here for slides "Take the Journey From Egg to Embryo"

1. Conception 
  • Formation of a viable zygote by the union of the male sperm and the female ovum; fertilization.
  • Normal hormonal balance, normal cycle, healthy pregnancy.
  • Normal gametes.
  • Healthy fallopian tubes - normal conduction of ovum, no ectopic pregnancy.
  • Healthy, normally positioned uterus, normal implantation.


2. Embryonic Development (4 - 8 weeks of embryo development):

1.5 Week

  • Completely developed embryo.

2nd Week

  • Primitive streak.

3rd Week

  • Central nervous system begins to develop.
  • Heart development initiated - beating begins.

4th Week

  • Complete mass (baby and chorion, etc.) - about 1" long and the size of a pigeon's egg.
  • Embryo inside is about 3/8" and weighs less than 1 gram.
  • Out-pouching from anterior brain - early eyes - limb buds of arms and legs.

5th Week

  • Nose and lips formation begins.
  • Brain is developed into 5 components and lumen of spinal cord is continuous with brain vesicles allowing free cerebral spinal fluid flow.

8th Week

  • Major organs begin development.
  • Now about size of hen's egg.
  • Embryo is 1" long and about 4 grams.
  • Hands and feet are seen.
  • Baby is extremely reactive to its environment.
  • Male sex hormone (testosterone) produced by testes
  • Masculine development in males - no change in females.

12th Week

  • Embryo is about the size of a goose egg.
  • Placenta is well established and weighs more than the baby.
  • Baby is approximately 3 1/2" long and weights about 60 grams (2 oz.). Fingers and toes can be seen.
  • This is the end of the embryonic stage.

3. Fetal Development:



14-16th Weeks

  • Brain developed to the point that baby can suck, swallow and make irregular breathing movements.

16th Week

  • 6", 6 oz. (180 grams)
  • Complete closure of nasal septum and palate.
  • Fetal heart beat heard with amplification.
  • Fetal movement is recognized.
  • Sex is distinguishable now.
  • Meconium formation in intestines.

pregnancy_ultrasound.jpg20th Week

  • 8", 10 oz. (300 grams).
  • Lanugo - fine hair covering over entire body, probably for protection of skin.
  • Vernix Caseosa - secreted by fetus, made of sebaceous material, and other materials and is probably protective. Has some antimicrobial substances.
  • Fetal heart beat heard: 120-160 beats per minute.

24th Week

  • 12", 1 1/2 lbs. (720 grams).
  • Baby is maturing, not considered viable (until 28 week).

28th Week

  • Baby can survive outside uterus if lungs capable of breathing.
  • 10-20% survival if born at this time.
  • 14", 2 1/2 lbs.
  • Viable (legally).
  • Fetus in breech position until 32nd week.

32nd Week

  • Maturing. 50% survival if born at this time.
  • Should turn to head down position.
  • 16", 3 1/2 lbs. (1680 grams).
  • Skin is red and wrinkly.
  • The downy type hair is less plentiful and has more vernix.

30-34th Week

  • Baby is the same size as placenta.

36th Week

  • 94% survival rate if born at this age.
  • 18", 5 1/2 lbs.
  • Has some subcutaneous fat.
  • The baby stores things during this last trimester.
  • Mother should watch her weight at this time.
  • Fingernails are now at the tips of the fingers.

40th Week

  • Full term. 20", 7 lbs. (3360 grams).
  • Length is better indication of maturity of fetus.
  • Very little lanugo, lots of vernix.
THIS ---->https://advancedhealth.chiromatrixbase.com/conditions/pregnancy/fetal-development3.html

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