Embryo SurvivalEmbryo Gene ExpressionEffect of Covariates on the Gene Expression Profile and Embryo Size on Day 7. Because the gene expression and embryos size on Day 7 are highly correlated, multivariate analysis can be used to assess the variables simultaneously and determine the role of different factors that produced them. The distribution in embryo cell number on Day 7 (based on stage) is log normal (Supplemental Figure S10; https:// doi .org/ 10 .3168/ jds .2017 -14306). The nanostring gene expression data on Day 7 is very well described by a log-normal distribution with a detection limit of 1. Embryo cell number on Day 7 and gene expression data were therefore log-transformed for analysis. A significant weak relationship was present between Day 7 progesterone and embryo cell number on Day 7 (R2 = 0.08; P = 0.01; Supplemental Figure S11; https:// doi .org/ 10 .3168/ jds .2017 -14306). However, BCS (P = 0.8), BCS change (P = 0.4), and DPP (P = 0.5) had no significant effects on Day 7 embryo size. A multivariate analysis indicated no effect of grade (1, 2, and 3) on the gene expression profile (P = 0.1). A multivariate analysis indicated no significant effects of Day 0 progesterone (P = 0.2), Day 7 progesterone (P = 0.5), BCS (P = 0.6), and DPP (P = 0.6) on the gene expression data (81 genes with gene expression greater than the limit of detection of the assay).