Jeffcott L B, Rossdale P D
J Reprod Fertil Suppl. 1979(27):563-9.
The position, posture and presentation of the fetus were studied by serial radiography of the abdomen in 18 crossbred Pony mares near term and during first- and second-stage labour. In 3 mares the fetal position was assessed before and after induction of parturition with the synthetic prostaglandin, fluprostenol. In late gestation and up to the time of first-stage labour the fetus lay in ventral position with the forelimbs and poll flexed or partly flexed. At this time fetal movements were confined to flexion and extension of neck and forelimbs, but at parturition the head and limbs gradually extended the the forelimbs, head and neck rotated so that dorsal position and cranial extension were achieved. From this position, with the forelimbs and muzzle engaged in the cervical canal, delivery was quickly effected. The trunk and hindlimbs came into dorsal position during second-stage labour. The mechanics of these fetal movements and their relation to causes of dystocia are discussed.
通过对18匹近足月、处于第一产程和第二产程的杂交母马进行腹部系列X线摄影，研究了胎儿的位置、姿势和胎位。对3匹母马在使用合成前列腺素氟前列醇引产前后评估了胎儿位置。在妊娠后期直至第一产程，胎儿呈腹位，前肢和头顶屈曲或部分屈曲。此时胎儿的活动仅限于颈部和前肢的屈伸，但在分娩时，头部和四肢逐渐伸展，前肢、头部和颈部旋转，从而达到背位和头向伸展。从这个位置开始，前肢和口鼻部进入宫颈管，分娩迅速完成。在第二产程中，躯干和后肢转为背位。讨论了这些胎儿运动的机制及其与难产原因的关系。
