Ultrasonographic diagnosis of twins in two pregnant bitches: case report

ABSTRACT Multiple pregnancies in humans account for only 3% of pregnancies, 97-98% of which are twin pregnancies and the morbimortality is higher in the monochorionic twins when compared to dichorionic ones. The canine species is naturally multiparous, but the diagnosis of monochorionic twin pregnancy is not common. The objective of this report was to describe the ultrasonographic diagnosis of monochorionic twin pregnancies in two bitches [Pug (case 1) and Shih tzu (case 2)]. It was possible to verify the presence of one gestational vesicle containing two fetuses in each female by observing two heads or two bodies within the same placental site. These fetuses presented adequate viability and normal organogenesis. Their development was similar to the other fetuses. In case 1 they were stillborn and smaller than the other five live-born fetuses. The twins in case 2 were born alive, but they also appeared smaller when compared to the littermates. The gestational risks associated with this condition in pregnant bitches are still unknown, however, there are reports of fetal death in monochorionic pregnancies in this species. Therefore, ultrasonographic exam during pregnancy allows an early monochorionic diagnosis and monitoring the fetal viability could bring health benefits to both the female and the littermates.

摘要 人类多胎妊娠仅占总妊娠数的3%，其中97%~98%为双胎妊娠；且单绒毛膜双胎（monochorionic twins）的病亡率高于双绒毛膜双胎（dichorionic twins）。犬类天生为多胎产仔物种，但单绒毛膜双胎妊娠的临床诊断并不多见。本报告旨在描述两只母犬（病例1为巴哥犬（Pug），病例2为西施犬（Shih tzu））的单绒毛膜双胎妊娠超声诊断结果。通过观察同一胎盘区域内的两个胎儿头部或体部，可确认每只母犬体内存在一个包含双胎儿的妊娠囊（gestational vesicle）。这两例的胎儿均具备良好的生存能力，且器官发生（organogenesis）正常，发育进程与其他胎儿无明显差异。病例1中的双胎为死胎，体型较其余5只活产幼崽更小。病例2中的双胎为活产，但相较于同窝幼崽仍显体型偏小。目前尚不明确母犬该类妊娠相关的妊娠风险，但已有该物种单绒毛膜妊娠出现胎儿死亡的相关报道。因此，孕期开展超声检查可实现单绒毛膜双胎妊娠的早期诊断，而监测胎儿生存能力可为母犬及同窝幼崽带来健康获益。