-
Within 12 hours
Fertilization -
Fertilized Egg
Begins to exist when sperm reaches the egg -
Hour 12
Pronuclei join together -
Zygote Stage Begins
Occurs when the 23 male chromosomes join the 23 female chromosomes -
40 hours
Second round of mitosis -
55 hours
Third round of mitosis -
Morula formed
after 3rd round of mitosis -
Embryo Stage Begins
Occurs when 3rd cleavage happens -
Day 6
64 cell embryo called a blastocyst -
Hatching
Happens after compaction, day 5-7 -
Day 9
Ectopic pregnancy could occur during implantation -
Day 9
Implantation -
Day 12
Disc with streak on the underside forms mesoderm -
Day 12
HCG begins to be secreted -
Day 15
First missed period -
Day 18
Neural tube forms -
Day 21
Heart begins to beat, arm & leg buds appear, yolk sac makes RBCs -
Day 35
Face plates forming -
6 weeks
Cleft lip or palate may occur -
6 weeks
Muscles form, bent neck, webbed hands and feet, segmented back -
7 weeks
Fingers & toes separate, eyes & ears formed -
Fetal Stage Begins
Occurs when all organs are formed, day 49 -
Day 50
Genitalia begins to differentiate, eyelids fuse, amnion surrounds fetus -
8 weeks
Eyes open, fat added under skin, head out of proportion to the body -
10 weeks
Chorionic villi sampling could be performed -
14 weeks
Amniocentesis could be performed
