The usual length of pregnancy is 40 weeks (nine lunar months).
- Only one out of hundreds of millions of sperm penetrates the ovum or egg and alters the surface of the egg so that no other sperm can enter.
- The genes (hereditary factors that determine our physical and emotional characteristics) of the sperm merge with those of the egg to create a new life.
- The cell that is formed multiplies to form a ball of cells called the embryo.
- By the end of two weeks the embryo attaches itself to the wall of the uterus to form the placenta through
which it will obtain all the necessary nutrients for growth and development from the mother.
DEVELOPMENT OF ORGANS & SYSTEMS
- At 3 weeks the heart begins to beat
- At 3 weeks the brain also begins to form
- At 4 weeks the arms and legs begin to develop
- At 6 weeks the eyes take shape
- By 8 weeks the basic structure of all the organs are in place
- At 12 weeks the genitals can be distinguished
GROWTH & FURTHER DEVELOPMENT IN UTERO
- At 20 weeks the baby begins to move about, weighs 460 grams and measures 19 cm in length. This is the earliest age at which a baby can survive if born at this time
- At 26 weeks the eyes open
- Between 25 and 40 weeks (the third trimester of pregnancy) - Baby’s weight triples and length doubles - Baby responds to sound, light & touch - Baby’s activity is influenced by mother’s diet, daily body rhythms & medication
- Baby takes his/her first breath as a result of sudden decompression of the chest and the sudden exposure to the external environment
- Fluid is expelled from the lungs and they become expanded with air
- The umbilical cord (the connection with the placenta) is cut
- Average birth weight is 3.2 kg (7.0 lb) and crown-heel length 50 cm (20 inches)