Abstract Labour challenges the newborn to adapt to extrauterine life and survive the troublesome neonatal period. Low vitality is a recurrent problem in veterinary perinatology, and several factors can directly or indirectly culminate in neonatal death. One prime determinant of low vitality in animals is foetal hypoxia resulting from prolonged labour or dystocia. Factors such as foetal acidosis, metabolic and electrolyte imbalances, and asphyxia can quickly lead to neonatal death, while others are a consequence of low vitality in which the weak neonate cannot reach the teat and feed, thermoregulate, or breathe because of airway obstruction by meconium. Neonatal hypoxia can also lead to a failure of passive transfer and neonatal infections. The birth weight, the age of the dam, the size of the litter, and parity are also relevant vitality determinants. Scoring systems, similar to the Apgar score used with human babies, have been modified in veterinary neonatology to identify low vitality neonates in need of medical intervention. This review focuses on the vitality assessments and risk factors associated with neonatal mortality in puppies, calves and piglets. Also reviewed is the relationship of umbilical cord morphology and hypoxia with the premature passing of meconium into the amniotic sac and subsequent aspiration into the lungs. Veterinary literature shows a need to improve Apgar scores in animals by using blood gases and other clinical and laboratory tests. Also, it is necessary to better train veterinarians and personnel to identify low vitality neonates and when necessary to implement a rapid medical intervention.