Macro and microscopic characteristics of the placenta and its relationship with the weight and the Apgar score of canine neonates

Abstract

The placenta is the main organ of pregnancy and is directly related to the proper development of the fetus. The correlation among some placental measurements and their respective neonates is widely studied in the human species. However, the studies regarding bitches are still limited. Therefore, the aim of this work was to evaluate if there is a relationship between placental weight and volume and the weight of neonates at birth in the canine species, as well as its influence on their viability. In this work, 7 bitches, 18 neonates and their placentas were evaluated. The weight of the placentas was measured using an analytical balance and the volume was calculated by measuring the volume of water displaced after placing it in a container of water. The neonates were weighed and classified according to the Apgar score after birth. Samples from each placenta were fixed in formalin and embedded in paraffin, then placed on slides and stained in hematoxylin and eosin. From these samples, the microvascular density (MVD) was calculated, as well as the presence or absence of necrosis, calcification and haemorrhage, classified in scores from 0 to 2. Data were analyzed using Kendall's test. The mean weight of the placentas was 29.11 ± 11.06 g and the volume was 21.33 ± 10.65 cm³. The mean weight of the neonates was 282.94 ± 123.28 g and the Apgar score was 8.83 ± 2.06. The mean MVD of the placentas was 0.04 ± 0.01. A positive correlation was observed between birth weight and placental weight and volume. Placental weight also positively correlated with placental volume. Also, no significant correlation was found between MVD and alterations with placental weight and volume and with the weight and Apgar score of neonates. Among the microscopic changes, only necrosis showed a moderate correlation with placental weight and volume. It can be concluded that the placenta has an influence on the weight of neonates, which is essential for its development in intra and extrauterine life. However, more studies are required in the described species, to better elucidate these questions.