Pregnancy First Trimester Pregnancy First Trimester

Fertilization :Fertilization :Combination of egg and Combination of egg and sperm sperm

Happens in fallopian tubes within hours Happens in fallopian tubes within hours of intercourseof intercourse

12 hours after cell division begins called 12 hours after cell division begins called zygotezygote

# of cells double every 12 hours (morula) # of cells double every 12 hours (morula) but overall size is the samebut overall size is the same

WEEK 2WEEK 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 dailySize and number of cells double daily End of “period of zygote”End of “period of zygote”

WEEK 3WEEK 3

Once implanted in uterus = embryoOnce implanted in uterus = embryo Backbone is forming Backbone is forming Brain is forming Brain is forming Primitive heart is beatingPrimitive heart is beating

WEEK 4WEEK 4

Arm buds Arm buds Leg buds Leg buds ¼ inch long ¼ inch long Doubling in size in one weekDoubling in size in one week

WEEK 5WEEK 5

Chest and Abdomen formingChest and Abdomen formingEyes are formed and can be seen Eyes are formed and can be seen

through clear eyelidsthrough clear eyelidsTail has disappearedTail has disappearedLungs begin to form Lungs begin to form Brain development continues Brain development continues 5/8 inch long5/8 inch long

Embryo at Approximately 6 WeeksEmbryo at Approximately 6 Weeks

WEEK 6WEEK 6

Teeth buds formed Teeth buds formed Fingers and toes buds are Fingers and toes buds are

formed formed 3/4 inch in size3/4 inch in size

The Developing EmbryoThe Developing Embryo

WEEK 7WEEK 7

Bones, muscles, and Bones, muscles, and cartilage formingcartilage forming

Internal organs can be seen Internal organs can be seen through clear skinthrough clear skin

WEEK 8WEEK 8

Face is formed Face is formed Arms, legs, and feet are partially Arms, legs, and feet are partially

grown grown Over 1 inch long Over 1 inch long End of “ period of embryo”End of “ period of embryo”

WEEKS 9-13 (entire Third Month)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 fetusHead is ½ the size of the entire fetus End of month: arms and legs moveEnd of month: arms and legs move Face can smile and frownFace can smile and frown Brain is more mature, but cannot thinkBrain is more mature, but cannot think Fetus is 3 inches longFetus is 3 inches long

Patterns of GrowthPatterns of Growth

1. Inside to outside1. Inside to outside Ex: the spinal cord developing before Ex: the spinal cord developing before

armsarms2. Head to foot:2. Head to foot: Ex: the brain begining development before Ex: the brain begining development before

legslegs3. Simple to complex3. Simple to complex Ex: the heart starting as a 3 chamber and Ex: the heart starting as a 3 chamber and

becoming a 4 chamber laterbecoming a 4 chamber later

Fetus at 16 Weeks GestationFetus at 16 Weeks Gestation

Stages of PregnancyStages of Pregnancy Developmental Stages: Developmental Stages: based on the based on the

development of the babydevelopment of the baby Period of the zygote weeks 0-2Period of the zygote weeks 0-2 Period of the embryo weeks 3-8Period of the embryo weeks 3-8 Period of the fetus weeks 9- birthPeriod of the fetus weeks 9- birth

Gestational Stages: Gestational Stages: based on an equal based on an equal division of time (13 weeks each)division of time (13 weeks each) 11stst Trimester weeks 1-13 Trimester weeks 1-13 22ndnd Trimester weeks 14-26 Trimester weeks 14-26 33rdrd Trimester weeks 27-40 Trimester weeks 27-40