The canine placenta is an underexamined organ. Placental abnormalities can affect foetus development and may be responsible for a low weight of the infant at birth; however, knowledge on their clinical significance in the canine species is limited. We aimed to describe macroscopic and microscopic findings in the canine placenta and amnion at term in clinically uncomplicated pregnancies and to evaluate their relationship with birth weight of healthy puppies. During natural delivery or C‐section, the birth weight of 82 puppies was recorded, 72 placentas and 66 amnions were recovered. The foetal and maternal surfaces of the placental girdle, marginal haematoma and amnion were evaluated. Each gross finding was recorded, morphometrically assessed and sampled for histological diagnosis. Furthermore, specimens of placenta and amnion were collected from representative areas and microscopic deviations from normal structure were evaluated in haematoxylin and eosin sections. Gross examination revealed ‘abnormalities’ in the 75.4% of the collected placentas. Necrosis was the gross change most commonly observed in the placental girdle (72.5%). Congestion (17.4%) and clotted blood/fibrinoid material (2.9%) were also observed. No gross changes of either the marginal haematoma or the amnion were recorded. Histologically, placental girdle showed necrosis (62.3%), mineralization (52.2%), congestion (36.2%) and neutrophilic infiltration (27.5%). Marginal haematoma exhibited mineralization (11.6%) and neutrophils (29%), while necrotic foci were rarely observed (4.3%). In the amnion, the most frequent alteration observed was hypertrophy of the epithelium (35.9%) followed by oedema (31.2%), mineralized foci (28.1%), fibrosis (23.4%), congestion (15.6%) and more rarely neutrophils (12.5%). Puppies’ birth weight was not statistically affected by either gross or histological abnormalities. Our study revealed that macroscopic and microscopic ‘abnormalities’ of the placenta and amnion may be common in uncomplicated pregnancies at term; however, no implications on puppies’ birth weight were observed. Deviations from ‘normal’ morphology of canine foetal adnexa warrant further investigation to assess their clinical implications if present.

中文翻译：

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足月时犬胎盘和羊膜的大体和组织学发现：什么是正常、异常或病理性的？

犬胎盘是一个检查不足的器官。胎盘异常会影响胎儿发育，并可能导致婴儿出生时体重偏低；然而，关于它们在犬科动物中的临床意义的知识是有限的。我们旨在描述临床无并发症妊娠足月时犬胎盘和羊膜的宏观和微观发现，并评估它们与健康幼犬出生体重的关系。在自然分娩或剖腹产期间，记录了 82 只幼犬的出生体重，回收了 72 个胎盘和 66 个羊膜。评估胎盘带、边缘血肿和羊膜的胎儿和母体表面。记录每个总发现，进行形态测量评估并取样用于组织学诊断。此外，从代表性区域收集胎盘和羊膜样本，并在苏木精和伊红切片中评估与正常结构的微观偏差。大体检查显示 75.4% 的收集胎盘存在“异常”。坏死是胎盘带中最常见的总体变化 (72.5%)。还观察到充血 (17.4%) 和凝血/纤维蛋白物质 (2.9%)。没有记录边缘血肿或羊膜的明显变化。组织学上，胎盘带显示坏死（62.3%）、矿化（52.2%）、充血（36.2%）和中性粒细胞浸润（27.5%）。边缘血肿表现出矿化 (11.6%) 和中性粒细胞 (29%)，而很少观察到坏死灶 (4.3%)。在羊膜中，观察到的最常见的改变是上皮肥大 (35.9%)，其次是水肿 (31.2%)、矿化病灶 (28.1%)、纤维化 (23.4%)、充血 (15.6%) 和更少见的中性粒细胞 (12.5%)。幼犬的出生体重在统计学上不受肉眼或组织学异常的影响。我们的研究表明，胎盘和羊膜的宏观和微观“异常”可能在无并发症足月妊娠中很常见；然而，没有观察到对幼犬出生体重的影响。犬胎儿附件“正常”形态的偏差需要进一步调查以评估其临床意义（如果存在）。幼犬的出生体重在统计学上不受肉眼异常或组织学异常的影响。我们的研究表明，胎盘和羊膜的宏观和微观“异常”可能在无并发症足月妊娠中很常见；然而，没有观察到对幼犬出生体重的影响。犬胎儿附件“正常”形态的偏差需要进一步调查以评估其临床意义（如果存在）。幼犬的出生体重在统计学上不受肉眼异常或组织学异常的影响。我们的研究表明，胎盘和羊膜的宏观和微观“异常”可能在无并发症足月妊娠中很常见；然而，没有观察到对幼犬出生体重的影响。犬胎儿附件“正常”形态的偏差需要进一步调查以评估其临床意义（如果存在）。