Fluoroscopic study of the birth posture of the sheep fetus.

Video-taped fluoroscopy was used in a research programme to review the characteristic attitudes of fetal limbs, head, neck and trunk, throughout the course of physiologically normal parturition in sheep. Nine fetuses from eight ewes were monitored during the whole process of natural birth by means of image-intensified X-ray fluoroscopy. All nine births were spontaneous and full term; with one exception they were unassisted. In all examinations the ewes were placed on their left sides on the X-ray table and lightly restrained with loose rope shackles. At parturition the ewes were fully conditioned to the examination procedure and had considerable limb mobility which allowed them to strain naturally during labour. No treatment was given to induce parturition or sedation. The consistency of observations was notable. A major finding was in the postural adaption of the forelimbs, taking the form of carpal extension with extreme flexion of the elbow and shoulder joints. This prepartum posture persisted throughout parturition in all monitored cases and is suggested as normal. The moulding effect of uterine contractions evidently acted on the hindquarters, contributing to their bunched (flexed) posture until mid-expulsion of the fetus. Full extension of all the hind limb joints occurred promptly when the fetal stifle region contacted the maternal pubis at terminal expulsion.