RESUMO
OBJECTIVE: To compare the influence of the obstetrical condition on neonatal respiratory performance, to estimate surfactant synthesis through lecithin and sphingomyelin ratio (L/S) in amniotic fluid of pregnant bitches and correlate the L/S with the respiratory condition during the first hour of life. DESIGN: Prospective randomized study. SETTING: University veterinary teaching hospital and private referral centers. ANIMALS: In accordance to the condition at birth, puppies from 25 healthy bitches aged 2-6 years were allocated into: Eutocia Group--EUT (n = 19 neonates and 14 bitches); Dystocia Group--DYS (n = 8 neonates and 5 bitches) and Elective Cesarean Section Group--CS (n = 12 neonates and 11 bitches). INTERVENTIONS: Amniotic fluid was drawn from amniotic sac and lecithin (L) and sphingomyelin (S) were measured by high performance liquid chromatography to obtain the L/S ratio. Neonatal physical examination was performed at 1, 5, and 60 minutes after delivery, and included the assessment of respiratory rate (RR) and respiration effort (RE). MEASUREMENTS AND MAIN RESULTS: CS group had significantly lower amniotic L/S ratio when compared to EUT and DYS. There were no significant differences between vaginal groups (EUT versus DYS) in respect to L/S ratios. RE of eutocic neonates improved promptly, while RE of DYS and CS groups improved only 1 hour following birth. Moreover, amniotic L/S ratio positively correlated with RR after 60 minutes. CONCLUSIONS: We identified a possible influence of the delivery method on the final surfactant maturation process. Thus, neonates born by elective CS prior to the onset of expulsive uterine contractions should have their respiratory parameters carefully monitored. Additionally, we propose that assessment of respiratory parameters 1 hour following birth can serve as a practical means to indirectly estimate pulmonary maturation (ie, surfactant synthesis) in puppies.