Transrectal Cranio-Cervical Dislocation of a Twin Fetus in a Mare

A 7-year-old Thoroughbred mare was diagnosed at 40 days gestation with twin fetuses adjacent to each other in the right uterine horn. At 66 days gestation, the mare was given flunixin meglumine (1 mg/kg IV), buscopan (0.4 mg/kg IV), altrenogest (0.044 mg/kg PO SID), and sedated with detomodine (0.006 mg/kg IV) and xylazine (0.3 mg/kg IV). Guided by transrectal ultrasound (7 mHz), the fetal head of the distal twin was stabilized transrectally between the thumb and forefinger. Dislocation was achieved by positioning the thumb at the base of the cranium and applying pressure side to side until a distinctive pop was felt and the thumb and forefinger could be placed between the head and the neck.1 Evaluations were performed one and two days later showed active heartbeats in both fetuses. One fetus appeared normal but the damaged fetus had hyperechoic debris in the fetal fluid and the head was visualized detached from the body. No evidence of the reduced fetus was apparent on ultrasound at 151 days. At 333 days gestation, the surviving foal was born without incident. The fetal membranes showed no abnormalities and no sign of the reduced twin was noted. The foal showed obvious congenital angular limb deformities with the right metatarsus caudally displaced to the tarsus, valgus deformities of both front legs and left hind, and abnormal ossification, particularly of the tarsal bones. After corrective measures, the foal showed moderate improvement, but prognosis for a future as a show horse is guarded.
The mare was rebred and confirmed to have a singleton pregnancy at 14 days gestation. Twin pregnancy is a major cause of pregnancy loss in horses. While early ultrasound diagnosis and transrectal manual reduction of the twin vesicle is very successful, reduction after Day 16 still provides a challenge to equine practitioners.2-5