Whelp Development Chart
Excerpted from the wonderful book, Canine Reproduction, by Phillis A. Holst, MS, DVM, this is a fascinating summary of prenatal development.
Following the "Average Day Post-Breeding" number is the estimated date, based on the date of Flame's last breeding (July 21, 2006).
| Average Day Post-Breeding | Stage of Development |
| 1 (July 21) | In estrust, pre-ovulation. |
| 2 (July 22) | Ovulation, primary oocyte. |
| 3 (July 23) | Primary oocytes have moved to distal portion of oviduct, meiosis is occurring. |
| 4 (July 24) | Secondary oocytes ready for fertilization. |
| 5 (July 25) | Fertilization occurs. |
| 6 (July 26) | First cleavage division of ovum begins. |
| 7 (July 27) | Two-cell embryo in oviduct. |
| 8 (July 28) | Four-cell embryo; going out of heat. |
| 9 (July 29) | 8-16 cells in a cluster. |
| 10 (July 30) | 16-32 cells, a morula. |
| 11 (July 31) | 32-64 cell morula enters the uterus. |
| 12-18 (Aug 1-7) | Blastocyst forms, floating free in uterus. Individual blastocysts become spaced evenly along horns of uterus. Grow from 1/4 mm to 2 mm in diameter. |
| 19 (Aug 8) | Implantation begins. Uterine response in a bandlike area around each embryo, suggesting the shape of the placenta that is developing for each embryo. |
| 20 (Aug 9) | Embryo body begins to take form as a linear thickening of cells, the primitive streak. |
| 21 (Aug 10) | Primitive body segments, or somites, begin to take form. |
| 22 (Aug 11) | Ten or more somites have formed. Primitive brain and spinal cord growing. Head portion of embryo bends forward. |
| 23-25 (Aug 12-15) | Limb buds form, embryo grows in length from 5 to 10 mm. |
| 26 (Aug 16) | Limb buds paddlelike, 11 mm. Swellings along uterus at site of each implantation may be large enough to palpate for pregnancy detection. |
| 27 (Aug 17) | Eyes begin to have pigment in retina, body taking form, face taking shape. Keeper is due to have her ultrasound. |
| 28 (Aug 18) | Facial features more defined, individual nipples are seen, 14-55 mm in length. |
| 29 (Aug 19) | Toes take shape, whisker buds are visible, umbilical cord forms, 18 mm long. |
| 30-32 (Aug 20-22) | Differentiation of detail of face & limbs until facial features are definitely doglike. 22 mm in length, 1 gram (1/30 oz.) weight. |
| 33 (Aug 23) | Male/female sexual characteristics can be differentiated. 24 mm in length. |
| 34 (Aug 24) | Digits & claws are differentiated. Eyelids, which are at first open, close. 30 mm in length, 2 grams weight. |
| 35-40 (Aug 25-30) | Growth & differentiation of external and internal details. Reaches 45 mm in length and 6 grams in weight. Skin pigment begins to be visible. |
| 41-63 (Aug 31-Sept 20) | Further growth and differentiation of the fetus. Puppies typically born between days 59-63. |