Transvaginal ultrasound-guided pregnancy reduction (TUGR) is a procedure described for
the management of twins post-fixation in the horse. Success rates are often disappointing
but are reported to be more favorable for bilaterally situated twins and when intervention
takes place before day 35 of gestation. This study aimed to determine whether stabbing the
embryo/fetus rather than aspirating conceptus fluids improved the likelihood of success,
measured as the birth of a normal live singleton foal. Data from 103 TUGR interventions
were analyzed by logistic regression analysis; method of treatment, relative conceptus
location (i.e., uni- vs. bilateral), and stage of gestation were included as interdependent
factors that potentially influence the outcome. Overall, 34/103 (33%) TUGR interventions
resulted in a single live foal. There was no significant difference (P ¼ 0.14) in the outcome
between TUGR based on fetal stabbing (12/28: 42.9%) versus fluid aspiration (22/75: 29.3%).
There was also no significant influence (P ¼ 0.11) of the conceptuses being located unilaterally
(19/65: 29.2%) versus bilaterally (15/38: 39.5%). However, TUGR was numerically
more successful (P¼0.05)when performed Day 35 of gestation (21/53: 39.6%), as opposed
to > Day 35 (13/50: 26%). Day 45 may represent an even more critical time point because
only 2 out of 15 TUGRs (13.3%) performed beyond this day resulted in the birth of a live foal,
compared with 11/35 (31.4%) performed between Days 36 and 45. Although the numbers are
low, this suggests that TUGR is not the method of choice for reducing > Day 45 twins. Four
pregnancy losses were recorded 1 to 7 months post-TUGR (4/38: 10.5%), and although it is
tempting to attribute the losses toTUGR, this rate of late gestation pregnancy loss is normal.
We conclude that TUGR by fetal stabbing does not offer significant advantages over fluid
aspiration. However, TUGR should be performed before Day 35 of gestation and is considered
primarily a salvage procedure to be used when re-breeding is not a viable alternative.