Phases of the Dog Embryo & Fetus

Fertilization

• 96 hrs.
  Divides into two cells
• 120 hrs.
  Divides into four cells
• 144 hrs.
  Divides into eight cells
• 192 hrs.
  The morula is constituted
• 9 days
  The morula installs itself in the uterus
• 15 days
  A blastocyte is formed, which is still floating around freely in the uterus
• 18 days
  The placentas are developed
• 20 days
  The ovules have changed in shape in order to become embryos that adhere to the walls of the uterine horns; the nervous system is already formed
• 28 days
  The embryos are already oval shaped & measure approx. 14-18 mm
• 30 days
  The sexual characteristics are already present and the eyes are covered by the eyelids
• 40 days
  The abdominal swelling is already noticeable in the mother, especially if there is a considerable number of puppies
• 45 days
  From this moment on, the growth of the fetus is very fast
• 51 days
  The bones of the fetuses are already calcified and therefore can be seen by means of x-rays in order to verify their positioning and approximate number
• 57 days
  The fetuses have already completed their prenatal development and are ready to be born. From the 58^th day on, whelping is imminent