With the birth of the Royal baby still very much at the forefront of the public’s mind, there was no question that this week I had to look at the use of veterinary ultrasound during pregnancy. Despite the successful fertilisation, and in some cases, fixation of multiple embryos during equine pregnancy, it is now well accepted that twin pregnancies are somewhat a rarity. Although there have been reported incidences of the survival of twin foals during pregnancy, it is the general consensus that twin equine pregnancies should be reduced wherever possible to reduce damage to the mare and/or the foal(s).

One way in which to detect the potential problem of the establishment of a twin pregnancy is to use veterinary ultrasound. Ultrasound can play a dual role here – not only can it help the breeder/farmer/veterinarian (delete as applicable) to visually identify a twin pregnancy, but it can also be used as a method by which to help eliminate one of the embryos.

Elimination of an embryo is a tricky business – the practitioner must be able to remove one embryo whilst simultaneously leaving the other intact and able to grow and develop into a fully-fledged foal. Research into this procedure has revealed that success rates are higher when embryo elimination is carried out earlier in gestation, although the percentage of mares that went on to have a single foal could still be much improved. A paper published by Journée SL. et al (Theriogenology, 2013 Jun 5, Epub ahead of print) revealed that 33% of pregnancies that were subject to embryo reduction resulted in the birth of a single foal, and that carrying out this procedure (transvaginal ultrasound-guided pregnancy reduction) before day 35 of gestation was most effective. In agreement, a paper published by Klewitz J et al. (J Am Vet Med Assoc, 2013 Feb 15: 242(4):527-32), suggested that embryo elimination (transvaginal ultrasound-guided aspiration) was most successful when carried out during early pregnancy, before day 43 of gestation. However, this study demonstrated relatively more success, with 49% of pregnancies resulting in the birth of a single foal. It should be noted that both of these studies were carried out independently and consequently the sample number differed.

It is interesting to note that there is a ‘natural’ alternative to the twin pregnancy dilemma, namely that leaving the pregnancy to progress normally can sometimes result in the natural elimination of the embryo. Alternatively, the decision to terminate the pregnancy can be taken, although the disadvantage here is that both embryos are lost and the mare will be required to fall pregnant all over again (Peter Fenton Equine Veterinary Practice Ltd)

The obvious question therefore is how can the outcome of this procedure be improved? Whatever the requirement for the establishment of pregnancy, it is important that pregnancy outcome is a success. Unfortunately, there is no ‘magic answer’, but continued research, alongside the use of veterinary ultrasound is sure to improve equine birth rates in the future.