Non-invasive detection method for screening for a well-developed blastocyst

A method of selecting, and then implanting, a selected human blastocyst into a human subject which comprises:

• (a) obtaining samples of biopsied human trophectoderm cells from each of multiple human blastocysts from a single donor;
• (b) constructing a DNA methylome library from, and sequencing the DNA methylome of, each of the samples of biopsied trophectoderm cells,
• (c) calculating the global DNA methylation level for each of the samples of the biopsied trophectoderm cells based on the sequences of the DNA methylome obtained in step (b) by counting (i) the number of methylated CpGs and (ii) the number of all CpGs and determining the ratio of (i) to (ii) for each of the samples and thereby the global methylation level of each of the blastocysts from which each sample of trophectoderm cells was obtained;
• (d) selecting the human blastocyst for use in implantation which has the global DNA methylation level which is closest to 0.30;
• and
• (e) implanting the human blastocyst selected in step (d) into the human subject.