Risk Factors for Acidosis or Difficult Clinical Presentation at Birth and Correlation with Unfavorable Early Neonatal Outcomes : A Hospital-Based Study

BACKGROUND: Whether low Apgar Score (AS) or evidence of umbilical cord acidosis (UCA) is the best predictor of early unfavorable neonatal outcome is still a matter of debate. The burden of these conditions in the whole population of liveborn infants, including preterm babies, and the association with maternal, obstetric and environmental risk factors have not been fully investigated. OBJECTIVE: To retrospectively analyse the distribution of UCA and/or low AS among babies born in a single neonatal tertiary care center over a 5 yrs-period (2005-2009) and to investigate the correlation with maternal, neonatal, obstetric and environmental variables. DESIGN/METHODS: A hospital-based case-control retrospective study was performed. Data on 33202 infants inborn were used. Inclusion criteria were (at least one): AS at 1'≤ 5, umbelical pH ≤ 7.05, BE ≤ -12 mmol/L. Controls were inborn and randomly selected in the same period. Maternal, obstetric and neonatal variables, day and time of delivery, early neonatal outcomes (intubation at birth and NICU admission) were recorded. RESULTS: 1529 cases (4.6% of liveborn babies; 822 male, GA 37.5±4 wks, BW 2946±847g) were compared to 1764 controls (5,3%; 822 male, 38.3±2.1 wks, BW 3182±567 g). The 2 groups were homogeneous. Low AS was reported in 26% of cases, UCA in 6.1%, low pH+low BE in 13.5%, low BE in 41%. At the multivariate analysis male sex (OR 1.2, CI 1.1-1.4), vacuum extraction (3.2, 2.3-4.6), birth during the night (1.3, 1.1-1.6), post-term (1.3, 1.0-1.6), VLBW (4.8, 2.4-9.4), ELBW (12, 5.5-29.1) significantly predicted UCA and/or low AS. Babies with low AS were more likely to be either intubated (36, 18.5-73.9) or NICU admitted (34, 25.2-48.4); while UCA (3.2, 1.69-6.11), UCA+low BE (5, 3.87-8.92) were only associated with a higher risk for NICU admission. Low BE alone wasn't associated with poor outcome. CONCLUSIONS: A difficult clinical presentation at birth is the major determinant for either resuscitation or NICU admission while UCA, mainly combined with low BE, only predicts need for further observation in NICU. Isolated abnormal BE is not a risk factor. VLBW and ELBW infants are at higher risk of a challenging presentation at birth. Environmental factors, such as delivery during evening time, might play a role.