How To Deal With Twin Conception

How To Deal With Twin Conception

Differential growth rates can be identified using ultrasound Frequently the conceptus which is small for its gestational age is the one that fails Resorption is more likely for conceptuses that fix within the same uterine horn. Some twin conceptions result in the birth of a single healthy foal, i.e. nature ensures that one pregnancy fails early enough to prevent interference with development of the other.


Coping with the problem The problem for the stud veterinarian is to decide whether and when to intervene. The decision must be made before day 33 if the mare is to stand a chance of getting in foal again during the same breeding season. Interference with a twin pregnancy can be by: abolition of the whole pregnancy by lysing the corpora lutea with prostaglandin. If initiated before day 36 the mare will usually have a normal subsequent heat with average fertility; attempts to do this after day 36 (when endometrial cups secrete eCG) may not succeed and are unlikely to be followed by a fertile heat.


Manual rupture of one conceptus is the usual course of action, The smaller conceptus should always be chosen. Early conceptuses (14-17 days) are not difficult to crush but as they are mobile in the uterine lumen they cannot always be easily fixed. As the conceptus develops from day 21 greater pressure is required to rupture it, and after day 25, repeated attempts may be required. As pregnancy proceeds after day 21, manual disruption of one pregnancy is more likely to be followed by death of the other, i.e. complete pregnancy failure.

The reason for this is not known but it may be related to the larger volume of conceptual fluid that is released. Bicornual pregnancies are most easily treated by this method, although gentle squeezing of two conceptions at the same site (unicornual) may be attempted in the hope that only one conceptus will be destroyed. In some cases it may not be possible to burst one conceptus; however, repeatedly squeezing it may cause sufficient damage that it subsequently resorbs.

Successful twin management usually requires early and repeated examinations. The initial ultrasound examination should be performed on day 14 or 15. Manual examinations after diagnosis and treatment of twins can confirm or otherwise the continuance of pregnancy. Ultrasound examination is superior, in the hands of an experienced clinician, as the course of development of twins or a surviving singleton can be monitored more accurately.