The process of placentation is essential for embryonic/fetal development and for a regular pregnancy. Proliferation, differentiation and cell death are the driving forces of placentation, determining the fate of trophoblast cells. Furthermore, angiogenesis is also part of the process of placentation and is related to a functional placenta. Thus, abnormalities at any stage of this development can lead to deficient or pathological placental function and, therefore, cause complications in pregnancy [1,2].

The placenta is responsible for several vital functions for the fetus, such as nutrition, gas exchange and excretion, which is directly related to its development [3]. Morphologically, the canine placenta belongs to the zonary type. It is composed of three distinct zones: the girdle, the marginal hematoma and the chorioallantoic membrane, in which the girdle forms a band that surrounds the fetus and acts as transfer zone to maternal and embryonic/fetal substances [4].

Studies in humans have already described that the assessment of the placenta can predict maternal and neonatal alterations, such as causes of miscarriage, prematurity or neonatal immaturity, among others [5]. Some studies have already correlated raw placental data – such as length, width, and weight – with negative perinatal outcomes, such as neonatal death [5,6]. Also, these data are even related to hypertension in adulthood [5,6]. In veterinary medicine, examination of the placenta is considered part of obstetric procedures in mares [7], and the proportion of sick foals is higher when placental abnormalities are observed [8,9]. Nonetheless, in bitches, this practice is not yet part of the obstetric routine.

In addition, studies have shown that pregnant women with preeclampsia have a lower placental weight and volume [10]. Therefore, it leads to newborns with lower weight [10]. Lower birthweight is related to the lower uteroplacental blood flow, lower concentration of growth factors and alterations in angiogenesis resulting from this pathology [10]. Low birth weight is one of the most important causes of weakness and death in neonates, with a negative influence on their future viability [11].

Therefore, this study aimed to verify if there is a relationship between placental weight and volume and canine neonates’ weight at birth. Furthermore, verify whether the placental weight and volume influence postnatal viability.