LORI.equine

Umbilical cord length and abortion

Keywords: abortion, equine, umbilical, cord, length

Abnormalities of the umbilical cord have been implicated as causes of abortion in mares. In some cases, a cord abnormality suggests strongly that it has resulted in abortion. In the absence of funisitis (inflammation of the umbilical cord) excessive length and twisting are two suggested causes. Some suggest that 6 or more twists my be abnormal but more twists than that can be seen in normal pregnancies. Sacculation of the urachus and mild contusions of the cord are less convincing as causes of abortion. Some data suggests that umbilical cords are longer in older mares and are in turn, associated with abortion. However, it is difficult to separate the effects of long umbilical cords from those of chronic endometrial fibrosis and other defects associated with aging.

Opinions vary as to how long a cord must be to be considered pathological. Some colleagues consider cords with a total length of more than 80 centimeters (intra- plus extra-amnionic) to be abnormal; others, over 100 cm. Therefore caution must be exercised in implying that the length of the cord has played a role in abortion. Many normal foals are born with cord lengths within the range of 80 to 100 cm. The reason for associating cord length with abortion is remains poorly understood but it may be related to disturbances of blood flow within the cord, especially when they are more than five or six twists in a cord.

In the following image, the two placentas are from two normal foals born on the same day. One has a cord that is 45 cm in length; the other, 92 cm.

Image size: 1500 x 948px

In the following case, the foal was also normal, yet the cord was more than 2 meters long. The extra-amnionic cord alone measured 200cm. With a modest 40cm added for the length of the intra-amnionic cord, the total length would have been approximately 240cm. Interestingly, the umbilical cord was unusually long during the previous foaling but its length was not recorded. It is not known if the sire was the same in both cases.

Image size: 1208 x 1036px. Copyright: Dr Cyril Stephen. Charles Sturt University. NSW.  Au. cyrilstephen@gmail.com

Image size: 1650 x 1409px

In the six month old fetus aove, the intra-amnionic cord alone was 75 cm in length. The extra-amnionic cord was not submitted because it was disposed of when the retained placenta had been expelled. Had that part of the cord been included, the total length would almost certainly been longer than 100cm. Even at term, that would have been considered to be long. Therefore abortion may indeed have been due to its long umbilical cord. In addition, there were 11 twists in the intra amnionic portion of the cord. Finally, the cord showed sacculations of the urachus. In normal foalings these urine-filled sacculations do occur but are not common. Insets show the length of the intra-amnionic cord and urine in a large sacculation.

In the main image, forceps have been inserted into the external orifice of the urachus, where urine drains into the allantois. The extra amnionic cord had been ripped off at this point, its vascular fragments visible adjacent to the forceps.

Note: Excessively short cords may also be abnormal. They have been implicated as a cause of premature rupture during the second stage of foaling and asphyxia

References:

Hong, C.B. et al. 1993  Equine abortion and stillbirth in central Kentucky during 1988 and 1989 foaling seasons. Vet Diagn Invest 5:560-566

Tengelsen, L.A. et al 1997. A 12-year retrospective study of equine abortion in Michigan Vet Diagn Invest 9:303-306

Whitwell. K.E. 1975. Placental pathology: Morphological studies on the normal singleton foal at term. Res. Vet. Sci. 19: 44-55.