For many a puppy’s development and birth can be as exciting as the birth of their own child. For those curious to know the development of a puppy week by week, feel free to look below. I’ll also be posting an article on the changes of the mother during her pregnancy process at a later date.

Week One (Fertilization to 7 days)

• Fertilization occurs
• Cell division occurs 12 hours after fertilization
• 2-celled embryo moves to the oviduct
• The embryo is fairly resistant to external interference in development

Week Two (Days 8-14)

• Embryo will be 4 celled at start of week and 64 celled by end of week (size of a poppy seed)
• Around day 10 embryo becomes 16-32 celled (now called a morula)
• Also around day 10 a 32-64 celled morula enters uterine horn
• Day 11 a fluid-filled inner cavity forms in the morula (now called a blastocyst)

Week Three (Days 15-21)

• Day 19 implantation occurs in uterus (size of a sesame seed)
• The embryo is sensitive to external interference in development
• Primitive body parts begin to form

Week Four (Days 22-28)

• Fetuses grow from 5-10 mm in length to 14-15 mm long (size of a pea to blueberry)
• Development of eyes and spinal cords
• Faces take shape
• Organogenesis begins – Embryos are highly susceptible to defects and external interference
• Day 25 ultrasound can be performed to visually see puppies
• Days 26 – 32 puppies can be palpated – this is the best time to palpate because the fluid amount increases after and it will be harder to palpate (this is something that should only be performed by those who have been trained)

Week Five (Days 29-35)

• Fetuses grow from 18 mm to 30 mm in length (size of a grape to a green olive)
• Development of toes, whisker buds, umbilical cord, and claws
• Now called a fetus and resemble a puppy
• Around day 33 gender can be determined
• Eyes now appear closed
• Day 30-32 Organogenesis ends – Embryos are fairly resistant to interference

Week Six (Days 36-42)

• Fetuses weigh around 6 grams and are 45 mm long (size of a small fig)
• Skin pigmentation visible
• Fetal heartbeats can be heard with a stethoscope
• Day 40-42 ossification of the bones begin

Week Seven (Days 43-49)

• Further growth and development continues
• Puppy Kicking can distinctly be felt towards the end of this week.

Week Eight (Days 50-57)

• Fetal count can be accurately measured via ultrasound or x-ray
• Around day 55 fetal movement can be detected
• Puppies are now viable and can safely be born from about day 56

Week Nine (Days 58-65)

• Final growth and development continues

Birth (Day 63)

• Puppies on average arrive at day 63 – however they can be born from day 56 to 65 without general complications

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