-
12 hours
Fertilization -
Fertilized Egg
Begins to exist when a sperm has fertilized the egg -
24 hours
Pronuclei join together -
Zygote stage begins
Occurs when both nuclei double to 46 chromosomes and fuse together -
30-36 hours
First round of mitosis (cleavage) -
40 hours
Second round of mitosis -
50-60 hours
Third round of mitosis -
Embryo stage begins
Occurs when the third round of mitosis is completed and is now called a morula -
Morula formed
-
Hatching
-
Day 6
4 cell embryo called a blastocyst -
Day 9
Ectopic pregnancy could occur -
Day 8-10
Implantation -
Day 12
hCG begins to be secreted -
Day 12
Disc with streak on the underside forms mesoderm -
Day 15
First missed period -
Days 14-22
Neural tube forms -
Day 21
Heart begins to beat, arm and leg buds appear, yolk sac makes RBCs -
Days 34-36
Face plates forming -
Days 34-36
Cleft lip or palate may occur -
Week 6
Muscles form, bent neck, webbed hands and feet, segmented back -
Week 7
Fingers and toes separate, eyes and ears formed -
Fetal stage begins
Occurs when all the organs are formed -
Day 50
Genitalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
Week 10
Chorionic villi sampling could be performed -
Weeks 14-15
Amniocentesis could be performed -
Months 6-7
Eyes open, fat added under skin, head out of proportion to the body
