Placental morphometric and hemodynamic parameters as predictors of early neonatal adaptation in dogs

Placental dysfunctions are associated with fetal restriction growth and unfavorable neonatal outcome, with reduced uteroplacental blood flow being one of the most frequent causes of placental insufficiency. This study compared fetoplacental Doppler ultrasonography throughout gestation and placental morphology of neonates presenting either high or low vitality at birth.

Puppies born by elective c-section were assigned to: High Vitality Group (vitality score ≥ 7, n = 10 and 7 bitches) and Low Vitality Group (<7, n = 12 and 8 bitches). Pregnant bitches were retrospectively evaluated by prenatal obstetric ultrasonography and Doppler of uterine and umbilical arteries. Placentas from each neonate were collected, macroscopically assessed and evaluated for morphometry via stereology and scored histological findings. During specific time-points of the postnatal period (0, 5-10, 60 min and 6 h), neonatal clinical evolution (peripheral oxygen saturation, lactatemia, weight, temperature and vitality - heart and respiratory rate, muscle tone, irritability reflex and mucous color) was monitored.

Hemodynamic indices of the uterine artery at late pregnancy (55-57 days) in Low-vitality Group were higher compared to High-vitality bitches. Significant reduction in fetal heart rate occurred as parturition approached, regardless of the experimental group. In the marginal hematoma region, glandular, junctional and lamellar zone, no significant differences were found between the High and Low Vitality Groups across placental morphological and stereological analysis, but specific placental features are related to neonatal outcome.

Neonatal vitality is unrelated directly to morphological characteristics of the canine placenta. However, uteroplacental hemodynamics assessed by Doppler ultrasonography during final gestation and changes in fetal heart rate near birth can predict neonatal clinical performance.