The aim of this study was to determine the biometric parameters of the embryo/fetus and to assess the haemodynamics in the umbilical artery during the first trimester of pregnancy in 14 Boer goats. All the goats under study had twin pregnancy. Gestational vesicle diameter (GSD), crown-rump length (CRL), biparietal diameter (BPD), occipital-nasal length (ONL), trunk diameter (TD) and the placentome diameter (PD) were measured from the 30th to the 45th day of pregnancy at 5-day intervals, using a B-mode ultrasound scanner. Measurements of blood flow parameters in the umbilical artery were made using a colour Doppler combined with a pulse wave Doppler technique. During the study period, there was a significant (P<0.05) increase in the diameter of the gestational sac and most of the biometric parameters of the embryo/fetus. The average CRL on day 45 was almost 10 times higher than that on day 30 of pregnancy. The peak systolic velocity in the arterial vessels on day 45 of pregnancy was higher (P<0.05) than that from 30 to 40 days of pregnancy. On the other hand, mean pulsation index (PI) at day 45 of pregnancy was lower (P<0.05) than that on day 30 and day 40 of pregnancy. No end-diastolic velocity was diagnosed in any goat during the study period. All parameters showed positive (P<0.01) correlations with the day of pregnancy, except the PI in the arterial vessels, which showed negative (P<0.01) correlation with the day of pregnancy. In conclusion, changes in the parameters of embryo-fetal morphometry, placentomes and blood flow parameters of the umbilical artery may be helpful in assessing the development of the embryo and the fetus during the first trimester of pregnancy in goats.