-
Start
Fertilization -
Fertilized Egg
Begins to exist when a sperm successfully penetrates the cytoplasm of the egg cell. -
12 Hours
Pronuclei join together -
Zygote Stage Begins
Occurs when the nuclei of the sperm and egg join together -
30 - 36 Hours
First round of mitosis (cleavage) -
40 Hours
Second round of mitosis -
50 - 60 Hours
3rd round of mitosis -
Morula Formed
-
6 Days
64 Cell embryo called a blastocyst -
Hatching
-
8 - 10 Days
Implantation -
8 - 10 Days
Ectopic pregnancy may occur -
Embryo Stage Begins
Occurs when the blastocyst implants into the uterine lining -
6th Week
Muscles begin to form, bent neck, webbed hands and feet, segmented back -
12 Days
hCG begins to secrete -
Day 12
Disc with streak on the underside forms mesoderm -
Day 14 - 22
Neural tube forms -
15 Days
First missed period -
Day 21
Heart begins to beat, arm & leg buds appear, yolk sac makes RBCs -
Fetal Stage Begins
Occurs during the end of the first trimester, when to fetus' organs begin to function properly -
Days 34, 35, and 36
Face plates form -
Days 34, 35, and 36
Cleft lip or palette may occur -
7th Week
Fingers & Toes seperate, eyes and ears formed -
Day 50
Genetalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
9 - 11 Weeks
Chorionic villi sampling could be performed -
14 - 15 Weeks
Amniocentesis could be performed -
28 Weeks
Eyes open, fat added under skin, head out of proportion to the body
