A primiparous mare foaled a live foal and a mummy. The mummy and its fetal membranes were necrotic and had been invaginated within the fetal membranes of the live foal. Near the mummy, the fetal membranes of the live foal had a clear demarcation between a ‘white’ and a ‘red’ region. The white region was touching the mummy, and some of its features were similar to those of a fetal–foot placental area of degeneration (PAD): it was ischaemic and degenerate (as indicated by hypoplasia, hyaline degeneration, multifocal squamous metaplasia, cell swelling and basement membrane sclerosis) with villi that were shorter than normal and limited in number. However, the PAD in this case was thinner than those in previous reports, and it was much larger, as it surrounded the entire mummy. The red region, which was touching the maternal endometrium, was hyperaemic, but in other respects, it was similar to the fetal membranes in the other uterine horn. To the authors’ knowledge, this is the first extensive report on the histology of type C twinning (i.e. with a mummified foal) in which the death of one foal had not been induced.

中文翻译：

---

母马 (Equus caballus) 双胎妊娠的大胎盘退化区域

一匹初产的母马产下了一只活的小马驹和一匹木乃伊。木乃伊及其胎膜已坏死，并已被内陷于活马驹的胎膜内。在木乃伊附近，活马驹的胎膜在“白色”和“红色”区域之间有明显的界限。白色区域与木乃伊接触，它的一些特征类似于胎足胎盘退化区（PAD）：它是缺血性和退化性的（表现为发育不全、透明变性、多灶性鳞状上皮化生、细胞肿胀）和基底膜硬化），绒毛比正常短且数量有限。然而，这次的PAD比之前报道的更薄，而且更大，因为它包围了整个木乃伊。接触母体子宫内膜的红色区域，充血，但在其他方面，它类似于另一个子宫角的胎膜。据作者所知，这是关于 C 型双胞胎（即木乃伊小马驹）组织学的第一份广泛报告，其中一只小马驹的死亡没有被诱导。