1. Pregnancy First Trimester Fertilization : Combination of egg and sperm Fertilization : Combination of egg and sperm Happens in fallopian tubes within hours of intercourse Happens in fallopian tubes within hours of intercourse 12 hours after cell division begins called zygote 12 hours after cell division begins called zygote # of cells double every 12 hours (morula) but overall size is the same # of cells double every 12 hours (morula) but overall size is the same

2. WEEK 2 Now a hollow ball of cells Now a hollow ball of cells “blastocyst” “blastocyst” Implanted in uterus Implanted in uterus Size and number of cells double daily Size and number of cells double daily End of “period of zygote” End of “period of zygote”

3. WEEK 3 Once implanted in uterus = embryo Once implanted in uterus = embryo Backbone is forming Backbone is forming Brain is forming Brain is forming Primitive heart is beating Primitive heart is beating

4. WEEK 4 Arm buds Arm buds Leg buds Leg buds ¼ inch long ¼ inch long Doubling in size in one week Doubling in size in one week

5. WEEK 5 Chest and Abdomen forming Chest and Abdomen forming Eyes are formed and can be seen through clear eyelids Eyes are formed and can be seen through clear eyelids Tail has disappeared Tail has disappeared Lungs begin to form Lungs begin to form Brain development continues Brain development continues 5/8 inch long 5/8 inch long

6. Embryo at Approximately 6 Weeks

7. WEEK 6 Teeth buds formed Teeth buds formed Fingers and toes buds are formed Fingers and toes buds are formed 3/4 inch in size 3/4 inch in size

8. The Developing Embryo

9. WEEK 7 Bones, muscles, and cartilage forming Bones, muscles, and cartilage forming Internal organs can be seen through clear skin Internal organs can be seen through clear skin

10. WEEK 8 Face is formed Face is formed Arms, legs, and feet are partially grown Arms, legs, and feet are partially grown Over 1 inch long Over 1 inch long End of “ period of embryo” End of “ period of embryo”

11. WEEKS 9-13 (entire Third Month) Beginning of “period of fetus” Beginning of “period of fetus” Fingernails appear Fingernails appear Head is ½ the size of the entire fetus Head is ½ the size of the entire fetus End of month: arms and legs move End of month: arms and legs move Face can smile and frown Face can smile and frown Brain is more mature, but cannot think Brain is more mature, but cannot think Fetus is 3 inches long Fetus is 3 inches long

12. Patterns of Growth 1. Inside to outside Ex: the spinal cord developing before arms Ex: the spinal cord developing before arms 2. Head to foot: Ex: the brain begining development before legs Ex: the brain begining development before legs 3. Simple to complex Ex: the heart starting as a 3 chamber and becoming a 4 chamber later Ex: the heart starting as a 3 chamber and becoming a 4 chamber later

13. Fetus at 16 Weeks Gestation

14. Stages of Pregnancy Developmental Stages: based on the development of the baby Developmental Stages: based on the development of the baby Period of the zygote weeks 0-2 Period of the zygote weeks 0-2 Period of the embryo weeks 3-8 Period of the embryo weeks 3-8 Period of the fetus weeks 9- birth Period of the fetus weeks 9- birth Gestational Stages: based on an equal division of time (13 weeks each) Gestational Stages: based on an equal division of time (13 weeks each) 1 st Trimester weeks 1-13 1 st Trimester weeks 1-13 2 nd Trimester weeks 14-26 2 nd Trimester weeks 14-26 3 rd Trimester weeks 27-40 3 rd Trimester weeks 27-40