Page 944 - The Veterinary Care of the Horse

sterile needle through the wall of the vagina and into the foetal sac under ultrasound

guidance.
VetBooks.ir 3 Abort the pregnancy and start again. This is only possible up to 35 days when the

endometrial cups develop. After 35 days, the pregnancy can be aborted but the mare is
unlikely to return to fertile oestrus within the same breeding season owing to continued

production of hormones by the endometrial cups.

Abortion of twins

Undetected twin pregnancies often end in abortion. If this occurs late in pregnancy, there is a
possibility of problems during delivery which can lead to loss of the mare. Twins that are

born alive are usually underweight and need a great deal of care. It is common for one or
both of them to die within a few days of birth. Those that survive are less likely to achieve a

high level of performance than single foals.

Abortion

The incidence of abortion in the last third of pregnancy is relatively low. However, even with
the best of care, some mares will not carry their foals to term.

POSSIBLE CAUSES OF ABORTION

These include the following.
• A twisted or abnormally long umbilical cord which restricts the circulation between the

foetus and placenta. The average cord length is 70 cm (28 in) but some are up to 110 cm
(43 in); it is thought that a longer cord is more likely to become tangled around the foetal

limbs or compressed (Figure 19.20).
• Infection: bacterial, fungal or viral (EHV-1, EVA).

• Twins: the placenta is rarely able to nourish two foals to full term.

• Maternal stress, e.g:

– malnutrition

– pain
– colic

– endotoxaemia, e.g. from serious types of colic

– a high temperature

– transport