library_construction_protocol: Virgin females of each strain were time mated at 12 weeks (±4 days) of age with stud males of the respective strain, with pregnancy (P) confirmed by the presence of copulation plug (gestational day (GD) 0.5). On GD6.5 dams were euthanized and the main conductive uterine artery isolated and cleaned of connective and adipose tissue and other vessels and snap-frozen for RNA extraction. Age-matched virgin SHRSP and WKY were used as non-pregnant (NP) controls).  Uterine arteries were harvested from the same horn which contained the most fetuses. Arteries were not harvested from a horn that had less than four fetuses. Arteries were dissected in calcium free physiological salt solution (PSS) solution.  Uterine artery RNA was extracted using the miRNeasy mini kit (Qiagen) according to manufacturer's instructions after homogenisation in Qiazol using TissueLyserII. Total RNA quality was assessed using a eukaryote total RNA picochip on an Agilent Bioanalyzer 2100 (Agilent Technologies, UK). RNA quality was accepted with a RIN >7. Total RNA libraries were prepared with ribosomal-depleted RNA using the Illumina TruSeq Stranded Total RNA with Ribo-Zero Gold kit (Illumina, USA), following manufacturer's instructions.