In the present study, seven mongrel bitches were used, their age ranged from 15 months to 3 years. Vaginal cytology was carried out during pregnancy period of these bitches by taking vaginal smears weekly to investigate vaginal cytological changes. Serial ultrasonography was performed daily on these bitches from the 15^th day after the last breeding until birth day to determine the time of appearance of different gestational structures. The first observation of the extra-fetal and fetal structures was as follows: The yolk sac membrane was first detected as an echogenic U-shaped fetal membrane in a range of 24-25 days. A third echogenic fetal membrane, allantoic membrane, was first detected on Day 27. On Day 23, in the uterine wall surrounding the gestational sac, an apparently hyperechoic inner layer was differentiated to the zonary placenta which appeared as two thick bands one on either side of the fetus on Day 29. The embryo appearance was on Day 20.5. The early time of the position of the embryo either opposed to the uterine wall or dependent on chorionic cavity was nearly on Day 22 and on Day 24, respectively. The heartbeat, which is one of fetal vital signs, was detected as a bright echogenic flickering motion on Day 21. On Day 26 in mongrel bitches, the features of the embryo changed from an oblong to bipolar shape and form two loops of number 8, size and density the same. An anechoic area in the head of the embryo was detected on Day 29. The limb buds were firstly detected on Day 29. Fetal movement was firstly detected on Day 33. Meanwhile, the skeleton of the fetus was first detected as hyperechoic structure on Day 33.