Prenatal diagnosis of twining in dogs and cats

Prenatal diagnosis is a set of investigations, both instrumental and laboratory, which aim to monitor some aspects of the health of the foetus during pregnancy, from the early stages of embryonic development to the mom ents preceding delivery. Maternal blood analyses and ultrasound are the main non invasive and safe techniques, while amniocentesis and chorionic villus sampling carry a minimal risk of miscarriage, in the human species (1,2). In companion animals, a growin g interest is emerging for the preterm ultrasound morphological screening of embryos and foetuses, aimed to assess the integrity and vitality of the conceptus as well as the early diagnosis of anomalies, which can cause complications in parturition. Among these, twinning has been poorly studied in dogs and cats, probably for the fact that most of the cases are not more recognizable at delivery. This study is a retrospective analysis of the ultrasonographic findings of twinning in the author's clinical activ ity from 2016 to 2022. Dichorionic dizygotic twins are the normality in the multiple offspring of dogs and cats, we considered twins only foetuses sharing the same allantoic sac (monochorionic twins). Only six cases of twinning were recorded, 2 in female cats and 4 in female dogs, out of the whole number of evaluations performed on 3120 foetuses (2640 canines and 480 felines), with an incidence of 0.4% and 0.2% in feline and canine foetuses (1.2% and 0.9% considering the mothers). All the twins had their a mniotic sac and umbilical cord but presented a single placenta and a unique allantoic sac (monochorionic diamniotic twins). No monoamniotic twins were found. Considering that no genetic assay was performed, the finding of opposite sex foetuses in 2/6 cases . Twinning may have an impact on the success of pregnancy, for the risk of dystocia, foetal or neonatal death, as observed in the reported cases. Prenatal ultrasound allows early recognition of twinning in dogs and cats. Planned C section is the main indic ation for twinning in this species.