Ultrasound‐guided fetal thorax compression to reduce post‐fixation twins in the mare

Abstract

BackgroundManagement of twin pregnancy after conceptus vesicle fixation in the horse is challenging because the reduction techniques described are either invasive, difficult to perform or associated with disappointing success rates.ObjectivesTo evaluate the success of transrectal ultrasound‐guided fetal thorax compression for reducing post‐fixation twin pregnancy in mares.Study designRetrospective clinical study.MethodsSixteen mares were presented for twin reduction between 51 and 79 days of gestation. History obtained from the owner and/or referring veterinarian detailed information regarding the mare (age, breed), pregnancy (day of gestation, dizygotic versus monozygotic twins, unilateral versus bilateral fixation), treatment and outcome (one live fetus at discharge; live singleton at foaling) after twin reduction. Transrectal fetal thorax compression was performed under ultrasound guidance by two experienced operators.ResultsOverall 9 of 16 twin pregnancies were successfully reduced and the likelihood of success was significantly higher in dizygotic than monozygotic twins. The procedure was successful in 9 of 10 dizygotic twins but unsuccessful in all six cases of monozygotic twins. Among the dizygotic twins, two mares lost the pregnancy after discharge from the clinic, seven mares delivered a healthy foal of normal size.Main limitationsSmall case number.ConclusionsTransrectal ultrasound‐guided fetal thorax compression is a minimally‐invasive and successful technique for reducing dizygotic twin pregnancies at approximately 2 months of gestation, but does not lead to any live births in cases of monozygotic twins.

Twin management in the mare: A review

“…The technique is performed by rectal manipulation and involves the isolation of the smallest or most easily accessible fetus with compression of its fetal neck/thorax between the ultrasound probe and the mare's pelvic brim/lateral abdominal wall by applying constant, increasing pressure to cause cardiac arrest, but without rupturing the chorioallantois. [51][52][53][54] Successful application results in faint valve movements or cardiac arrest immediately after performing the reduction or within 24 h. Cardiac arrest can be presented after a single session, however manipulation may need to be repeated on consecutive days. 52 The combination of a tocolytic, spasmolytic drug and NSAIDs can be administered at the time of the procedure to facilitate the isolation of the fetus, prevent rectal straining and inhibit prostaglandin release.…”

“…[51][52][53][54] Successful application results in faint valve movements or cardiac arrest immediately after performing the reduction or within 24 h. Cardiac arrest can be presented after a single session, however manipulation may need to be repeated on consecutive days. 52 The combination of a tocolytic, spasmolytic drug and NSAIDs can be administered at the time of the procedure to facilitate the isolation of the fetus, prevent rectal straining and inhibit prostaglandin release. In addition, post-reduction treatment, including NSAIDs and progestin therapy can be administered, however this does not seem to be critical.…”

“…In addition, post-reduction treatment, including NSAIDs and progestin therapy can be administered, however this does not seem to be critical. 52 Regular ultrasonographic monitoring following this procedure is suggested to assess both the demise of the reduced fetus and the viability of the remaining fetus as an unsuccessful outcome is often not immediately apparent and abortion usually only occurs about 1 month after the procedure. 52,53 The thoracic compression technique is currently favoured and most effective between 55 and 65 days of gestation [52][53][54] and a live foal success rate of 60% (6/10; unilateral fixed twin pregnancies) can be expected.…”

“…52 Regular ultrasonographic monitoring following this procedure is suggested to assess both the demise of the reduced fetus and the viability of the remaining fetus as an unsuccessful outcome is often not immediately apparent and abortion usually only occurs about 1 month after the procedure. 52,53 The thoracic compression technique is currently favoured and most effective between 55 and 65 days of gestation [52][53][54] and a live foal success rate of 60% (6/10; unilateral fixed twin pregnancies) can be expected. 53 Recently, Arnold et al 52 also reported a successful reduction to a singleton in 9 out of 10 (90%) dizygotic twins, seven of which have resulted in the birth of a normal sized single foal (70%).…”

“…52,53 The thoracic compression technique is currently favoured and most effective between 55 and 65 days of gestation [52][53][54] and a live foal success rate of 60% (6/10; unilateral fixed twin pregnancies) can be expected. 53 Recently, Arnold et al 52 also reported a successful reduction to a singleton in 9 out of 10 (90%) dizygotic twins, seven of which have resulted in the birth of a normal sized single foal (70%). Disadvantages and factors that negatively impact the outcome are: time spent to perform the procedure, multiple manipulations in consecutive days, operator's experience and insufficient isolation of the targeted fetus.…”