Articles
Fetal development: The first trimester
Week 5: Hormone levels increase
Week 7: Baby's head develops
Week 8: Baby's nose forms
Week 9: Baby's toes appear
Week 10: Baby's elbows bend
Week 11: Baby's genitals develop
Week 12: Baby's fingernails form
Content
Weeks 1 and 2: Getting ready
Week 3: Fertilization
Week 4: Implantation
Week 5: Hormone levels rise
Week 6: The neural tube closes
Week 7: The head develops
Week 8: The nose forms
Week 9: Toes appear
Week 10: The elbows bend
Week 11: Genitals develop
Week 12: Fingernails form
Week 7: Baby's head develops
Week 8: Baby's nose forms
Week 9: Baby's toes appear
Week 10: Baby's elbows bend
Week 11: Baby's genitals develop
Week 12: Baby's fingernails form
Content
Weeks 1 and 2: Getting ready
Week 3: Fertilization
Week 4: Implantation
Week 5: Hormone levels rise
Week 6: The neural tube closes
Week 7: The head develops
Week 8: The nose forms
Week 9: Toes appear
Week 10: The elbows bend
Week 11: Genitals develop
Week 12: Fingernails form
Week 4: Implantation
Once it reaches the uterus, the morula becomes what's called a blastocyst. The rapidly dividing ball of cells begins to burrow into the uterine lining. This process is called implantation.
Within the blastocyst, the inner group of cells will become the embryo. The outer layer will give rise to part of the placenta. The placenta nourishes the unborn baby throughout pregnancy.
