Table I.

Definitions and description of measures used to quantify gestational age and gestational age acceleration

1. Clinically estimated gestational age: Gestational age at birth as determined in routine clinical care through measurements on ultrasound before 20 wk, or menstrual history if no ultrasound dating was available

2. DNAm gestational age: Gestational age at sample collection predicted from DNAm. This measure is highly correlated with gestational age, but differences between gestational age and DNAm gestational age are observed and may reveal an infant’s developmental maturity.

3. Gestational age acceleration: Calculated as residual of an individual proband’s DNAm gestational age onto the regression curve of gestational age and DNAm gestational age for the complete cohort. This measure is used to assess an infant’s developmental maturity. A positive gestational age acceleration indicates a more mature infant than their gestational age suggests and a negative gestational age acceleration indicates a less mature infant than their gestational age suggests. It is important to note that gestational age acceleration is independent of gestational age.