The Maternal Blood Transcriptome Reflects Molecular Signatures Associated With Large Offspring Syndrome and Other Adverse Pregnancy Outcomes in Cattle.

Large offspring syndrome (LOS) in cattle is a phenomenon characterized by fetal overgrowth that is largely associated with calves derived from in vitro produced embryos. Here it was tested whether occurrence of LOS as well as two other adverse pregnancy outcomes, stillbirth and abortion, could be predicted using changes in the maternal blood transcriptome early in gestation. Blood samples were collected from Holstein and crossbred heifers at 40-50 days of gestation following embryo transfer of in vitro produced embryos. A total of 203 samples were selected for RNA-sequencing and used to compare recipients of embryos resulting in live-born calves of normal birth weight (control; n = 96) with recipients of embryos resulting in LOS calves (n = 15), stillbirths (n = 43), and abortion before 210 days of gestation (n = 49). Large offspring syndrome was defined based on birth weights greater than 2 standard deviations from the mean. The number of differentially-expressed genes (p < 0.01) was 32, 176, and 100 for comparisons of control versus LOS, stillbirth and abortion, respectively. Biomarkers were identified in a randomly selected, balanced training dataset using Random Forest after filtering for differential expression. Markers were then tested in the held-out dataset through 6 machine learning models. The best biomarkers consisted of 26, 24, and 28 genes for LOS, stillbirth and abortion, respectively. The accuracy of prediction ranged from 0.91 to 0.965 for LOS, 0.73 to 0.98 for stillbirth, and 0.62 to 0.96 for abortion. Despite the relatively small sample size, the model demonstrated high sensitivity for LOS classification, supporting that the maternal blood transcriptome in early pregnancy reflects molecular alterations associated with fetal overgrowth that can be predictive of the condition.