Total RNA was isolated from placental samples using the RNeasy Mini Kit (Qiagen, Valencia, CA) and stored in RNAse-free water at −80°C (12 (link)). Yields were quantified using a Qubit Fluorometer (Thermo Scientific, Waltham, MA) and an Agilent Bioanalyzer was used to assess integrity (Agilent, Santa Clara, CA). Ribosomal RNA was removed using a Ribo-Zero Kit (39 (link)), with the remaining RNA converted to cDNA using random hexamers (Thermo Scientific, Waltham, MA). The HiSeq 2500 platform (Illumina, San Diego, CA) (40 (link)) was used to assess transcriptome-wide 50 bp single-end RNA-seq, which was conducted in three sequencing batches and samples were randomized across batches; 10% of samples within each batch were run in triplicate.