Ψ The Germinal Period: From the moment of conception until 14 days later. The first 7- 10 days constitute a dangerous journey as the zygote moves down the fallopian tube to implantation in the uterus where it can be nourished. Rapid cell division & the beginning of cell differentiation follows.
Ψ The Period of the Embryo: From 14 days until 56 days after conception. During this time all major external & internal body structures begin to form.
Ψ The Period of the Fetus: From the ninth week after conception until birth. Age of viability (about 22 weeks).
Ψ Vulnerability During Prenatal Development
The Germinal Period: About 60% of all developing organisms fail.
The Period of the Embryo: About 20% of embryos are aborted spontaneously.
The Period of the Fetus: About 5% of all fetuses are lost.
Birth: About 31% of all zygotes (conceptions) grow & survive.
Growth & Development|
Robert C. Gates