Peripheral whole blood was collected in cfDNA BCT tubes (Streck, catalog 230470) then plasma isolated within 30 minutes and frozen. cfDNA was isolated from 1 mL of plasma using using the QIAampMinElute ccfDNA Mini Kit (Qiagen Catalog 55204).  Methyl-seq libraries were prepared using NEBNext EM-seq Kit (New England Biolabs Catalog E7120S) from 10 ng cfDNA (or all cfDNA isolated if < 10 ng isolated for the sample). cfDNA was not sheared for sequencing. 20 pg of unmethylated lambda DNA and 1 pg of methylated pUC19 DNA, were spiked into the input cfDNA to determine the C-U conversion efficiency of methylation libraries. Lambda phage and pUC19 DNA spike-ins were used to assess conversion and off-target conversion efficiency for each sample. All samples had above 97% conversion and off target conversion below 1.7%. Indexed libraries were pooled, spiked in with 10% PhiX, and sequenced with run of 2 × 150bp+8 bp using NovaSeq 6000 S4 Reagent Kit v1.5 (300 cycles) (Illumina Catalog 20028312). Coverage was between 8× and 24× for all but one sample (exception was one 16-wk sample with coverage of 4.8×), with mean of 16× and median of 15×. The BAM file was produced by (1) removing duplicate reads, (2) filtering out spike-in reads that aligned to phiX, lambda phage, or pUC19 genomes, then (3) aligning the remaining reads to GRCh38. (For alignment results of spike-in control reads please refer to Supplemental Dataset S21 of our publication: https://doi.org/10.1073/pnas.2406954122)