Figure 1

Effect of hatching site on the hatching process. (a) Schematic of the morphology of angle measurements of blastocyst hatching sites. During the measurement, two lines were drawn, the tangent line of the ICM arc midpoint and a straight line connecting the hatching site to the ICM arc midpoint. The acute angle between two straight lines is the hatching angle θ. (b) Sorting of blastocysts. Left, middle and right are representative of the hatching blastocysts 0° ≤ θ ≤ 30°, 30° < θ ≤ 60°, and 60° < θ ≤ 90°, respectively. The dotted line marks the ICM circle arc. Scale bar = 50 μm. (c) Percentage of hatching blastocysts 100 hours after administration of human chorionic gonadotropin (hCG) to the 1,827 blastocysts with natural hatching sites. Data were analysed by chi-square test. Percentages without a common letter (a–d) differs (P < 10⁻⁴).