Gestational Age Clocks
The cell type specificity of DNAm has complicated the use of the
epigenetic clock to study pre-natal environmental
exposures74 as the
composition of cord blood is distinct from venous blood, thereby
rendering clocks developed using venous blood unsuitable for gestational
epigenetic age (GEA) predictions. The Horvath pan-tissue clock
incorporated cord blood samples in its training set but set their CA at
“0”75. This may lead
to lower accuracy in neonatal blood samples as it does not account for
their actual gestational age. Since then, gestational epigenetic clocks
have been developed as summarized in Table 2 .
The study of the relationship between maternal exposures and DNAm has
expanded rapidly. However, some studies use gestational age (as
estimated through either last menstrual period or ultrasound
methods)24 while others
use GEA. Much like the use of EAA in childhood and adult studies, GEA
can provide insight into the role of DNA methylation in traits in
infancy.