Title:
Gestational age versus birthweight to predict outcomes in neonates with extreme prematurity

Authors:
Elizabeth B. Ausbeck MD¹, P. Hunter Allman MS², Jeff M. Szychowski PhD^1,2, Akila Subramaniam MD, MPH¹, Anup Katheria MD³

 Institutions:

¹Department of Obstetrics and Gynecology, Center for Women’s Reproductive Health, University of Alabama at Birmingham, Birmingham, AL

²Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL

³Neonatal Research Institute, Sharp Mary Birch Hospital for Women and Newborns, San Diego, CA

Background:

• Delivery <28 weeks’ gestational age (GA) accounts for the majority of neonatal morbidity and mortality
• -GA is the main determinant for antepartum/delivery interventions
• Many centers also incorporate estimates of fetal weight, with certain thresholds below which fetal interventions may not be offered

Objective:

• To evaluate the predictive value of birth gestational age (GA) and birthweight (BW), independently and combined, for neonatal mortality and morbidity in a contemporary cohort of extremely preterm infants

Study Design:

• Secondary analysis of multicenter RCT (PREMOD2) that compared umbilical cord milking to delayed cord clamping in premature newborns
• Inclusion criteria:

• • GA 23⁰-27⁶ weeks

• Exclusion criteria:

• • Major congenital anomalies
  • Severe placental abruption
  • Transplacental incision
  • Umbilical cord prolapse
  • Hydrops fetalis
  • Placenta accrete with bleeding accrete
  • Monochorionic multiple gestations
  • Fetal or maternal risk for severe compromise at delivery
  • Inability to return for 24-month neurodevelopmental testing

• Primary outcomes:

• • Neonatal death
  • Composite of severe neonatal morbidity (components in Figures)

• Analysis

• • Multivariable logistic regression used to model outcomes based on GA, BW, or both GA&BW as primary independent predictors
  • Receiver operator characteristics (ROC) curves and area under the curve (AUC) were determined for the 3 models
  • AUCs were compared with contrast matrices to determine if GA, BW, or GA&BW had superior ability to predict the primary outcomes
  • Planned subgroup analysis for small for gestational age (SGA) infants

Results:

• Of 474 neonates in the RCT, 182 (38%) were included in this analysis
• Neonatal death occurred in 15% (n=27)
• Severe neonatal morbidity occurred in 76% (n=139)
• Figure 1

• • No significant difference in the predictive value for neonatal death based on GA, BW, or GA&BW (AUC_GA=0.85, AUC_BW=0.85, AUC_GA&BW=0.86)
  • Also no significant difference in the predictive value for severe morbidity based on GA, BW, or GA&BW (AUC_GA=0.81, AUC_BW= 0.80, AUC_GA&BW = 0.82)

• Figure 2

• • For SGA infants, no difference in the predictive value for either outcome based on GA, BW, or GA&BW

Conclusions:

• GA and BW are both good predictors of neonatal morbidity and mortality in severely preterm neonates
• Combining the two is not more predictive than either alone, even in SGA infants