During the course of pregnancy, nature takes a microscopic dot of life and creates a 7 lb. baby in only nine months. Fetal development is explosive, particularly in the first few months.
Weeks 1-4
The first four weeks of pregnancy include two weeks before ovulation. The zygote forms and implants by Week 4.
Weeks 5-8
Week 5 starts the embryonic period, according to the Mayo Clinic. The embryo is made up of three layers that will differentiate shortly. Week 6 brings the fetal heartbeat, and a small arm and leg buds appear. The brain starts developing in Week 7, and by Week 8, the embryo begins to move.
Weeks 8-12
In weeks 9 and 10, facial features form, and genitalia start to differentiate in Week 11.The 2-inch baby is now a fetus.
Weeks 12-20
Hair begins to grow and the first stool forms in the intestine. You might feel movement by 16 to 18 weeks. The baby's sex can be seen on ultrasound by Week 20.
Weeks 20-40
Small details and growth occur in these weeks; toenails appear by Week 24. Lungs can function with help by Week 24, and the baby grows from 6 inches and 9 oz. in Week 20 to 7 lbs. and 20 inches by Week 40.
