Stages of Fetal Development
2. Embryonic Development
3. Fetal Development
Click here for slides "Baby's Journey in The Womb"
Click here for slides "Take the Journey From Egg to Embryo"
- 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):
- Completely developed embryo.
- Central nervous system begins to develop.
- Heart development initiated - beating begins.
- 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.
- 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.
- 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.
- 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:
- Brain developed to the point that baby can suck, swallow and make irregular breathing movements.
- 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.
- 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.
- 12", 1 1/2 lbs. (720 grams).
- Baby is maturing, not considered viable (until 28 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.
- 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.
- Baby is the same size as placenta.
- 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.
- Full term. 20", 7 lbs. (3360 grams).
- Length is better indication of maturity of fetus.
- Very little lanugo, lots of vernix.