Estimating the survival of extremely preterm newborns or determining the risk of disabilities after they are born is based on gestational age and estimated weight. Obstetric dating of gestational age is accurate within 3 to 5 days during the first trimester and only 1 to 2 weeks during the second and third trimesters. Likewise, fetal weight is estimated with 15–20% accuracy and is prone to errors in cases of intrauterine growth restriction. A discrepancy of 1–2 weeks estimated gestational age or a 100–200 g difference in birth weight has significant implications for survival and long-term morbidity. 

Other factors involved in the newborn’s prognosis are the presence of obstetric complications, the status of maternal health, and genetic factors that may affect the outcome. There are tools available to prognosticate these high-risk newborns. These tools factor in gender, antenatal steroid use, and multiplicity. To best apply them to an individual patient, the provider must be aware of the study design behind them.