Serial ultrasonographic examinations were performed on 9 Miniature Schnauzer bitches from day 15 of gestation until parturition to determine the ultrasonographic measurement of gestational structures. Ovulation was designated the day that plasma progesterone concentration exceeded 4.0 ng/ml (day 0). Extra-fetal structures were measured from day 17 or 18 to 60. Outer uterine diameter (OUD) increased from $6.50{pm}1.06mm$ ($Mean{pm}SD$) to $50.89{pm}5.62mm$, inner chorionic cavity diameter (ICCD) increased from $2.10{pm}0.15mm$ to $37.15{pm}4.36mm$, and length of placenta (PL) increased from $7.50 {pm}1.41mm$ to $40.62{pm}3.27mm$. OUD and ICCD were significantly and linearly relative to gestational age especially through day 37, whereas PL was not significantly relative to gestational age. Of the extra-fetal structures, ICCD was the most accurate for estimation of gestational age before day 38 of gestation. Fetal structures increased at a linear rate to parturition. Fetal crown-rump length (CRL) increased from $2.55{pm}0.07mm$ on day 22 to $85.25{pm}9.89mm$ on day 48. Fetal head diameter (HD) increased from $3.43{pm}0.64mm$ on day 27 to $25.06{pm}0.41mm$ on day 63. Fetal body diameter (BD) increased from $ 5.96{pm}0.84mm$ on day 30 to $43.76{pm}3.36mm$ on day 63. Of the fetal structures, HD was the most accurate for estimation of gestational age after day 38 to parturition.