Assessment of fetal growth by B-mode and doppler ultrasonography in rabbit during pregnancy

The objective of this study was to evaluate the biometric parameters of rabbit foetuses and haemodynamic changes in a. umbilicalis blood flow during gestation. Ten healthy New-Zealand white female rabbits weighing 3.6 - 4.1 kg were studied. The day of controlled mating with sexually active bucks, was considered Day 0 of pregnancy. On days 7-9 post-mating, pregnancy diagnosis was confirmed by ultrasonography using a micro convex probe of 8 MHz. B-mode and Doppler ultrasonography were performed at 3-4 day intervals until delivery. The measurements of Crown-rump-length (CRL) Bi-parietal diameter (BPD), Trunk diameter (TD) were recorded from the most caudal foetus, positioned in the left uterus horn. Additionally, Foetal-Heart-Rate (FHR), arterial pulsatility and resistance indices (PI, RI) were evaluated from the mid-cord site of the umbilical cord. Parturitions were occurred at 28±0.5 day (SEM) after mating normally. CRL and TD values were in high positive correlation with the gestational age (r=0.972; p<0.001). Of these parameters, BPD values was the most correlated with the gestational age (r=0.981; p<0.001) and were able to measurable in second and third trimester practically. Meanwhile CRL values were recorded in only second trimester due to possibility of fitting on the screen. FHR was in positive correlation with the gestational age (r=0.562; p<0.001) and increased gradually as the pregnancy progressed. Peak values of FHR were recorded on 20th day and decreased on 27th day of pregnancy (p<0.05). Pulsatility and resistance indices negatively correlated with gestational age (r=-0.383; p<0.01) and (r=-0,730; p<0.001), respectively. PI value has not significantly change during pregnancy. From day 20 onwards, RI of umbilical artery decreased (p<0.01), after then, RI curve was stable until parturition. In contrast to other domestic species, the FHR curve ascending along with the progressive of second third of pregnancy is remarkable. This work provides additional values that might be useful when evaluating foetal growth and functional haemodynamic changes of foetuses in rabbit pregnancies and may be used in further studies.