Figure 1.

Study design and methodology. Illumina 450K datasets of fetal placenta samples were downloaded from GEO and restricted to those from normal/typical pregnancies to the fullest extent possible (see “Methods”). Samples were classified into 4 groups according to annotated gestational age, and each dataset was processed through identical subject and probe level QC steps. Single site and region-based analyses were performed in full term samples first, and then also performed in individual trimester datasets to examine replication of full term findings. See “Methods” for additional details.