Post-warming embryo morphology is associated with live birth: a cohort study of single vitrified-warmed blastocyst transfer cycles.

PURPOSE: This study aims to examine whether blastocyst morphology post-warming correlates with live birth. METHODS: In this cohort study, morphological characteristics post-warming were reviewed in all single vitrified-warmed blastocyst transfer cycles performed between November 2016 and May 2017. Immediately before transfer, the degree of blastocoel re-expansion was graded as A, fully expanded; B, partially expanded ≥ 50%; C, partially expanded < 50%; and D, collapsed. The degree of post-warming cell survival was graded on a scale of 50 to 100% and was then classified into 4 groups: very low 50-70%, low 71-80%, moderate 81-90%, and high 91-100%. RESULTS: Overall, 612 cycles were reviewed, of which 196 included PGT-A tested embryos. The live birth rate (LBR) increased from 11.4% in the collapsed blastocysts group to 38.9% in the post-warming full re-expansion group (p < 0.001) and from 6.5% for blastocysts with a very low cell survival rate to 34.7% for blastocysts with high cell survival rate (p = 0.001). LBR was 6.7% for blastocysts with the worst post-warming morphological characteristics, namely, collapsed with very low cell survival rate. On multivariate analyses, partial blastocyst re-expansion ≥ 50%, full re-expansion, and high cell survival rate remained significantly associated with live birth, after controlling for female age, pre-vitrification morphological grading, and PGT-A. A sub-analysis of cycles using PGT-A tested embryos showed similar results. CONCLUSION: Post-warming re-expansion and high cell survival rate are associated with higher LBR in euploid and untested blastocysts. However, embryos with poor post-warming morphology still demonstrate a considerable probability of live birth, and they should not be discarded.

Revisiting Isaac Newton's Index Chemicus: A Response to Richard S. Westfall.

Previous attempts to date the five editions of Isaac Newton's Index Chemicus found in Keynes MS 30 (King's College Library, Cambridge University) have relied on an incomplete examination of the citations Newton provides for his references. This study shows that a full examination of all Newton's citations provides a more accurate method of dating, and thus pushes the timeline of production for all versions forward several years from the early 1680s to the early 1690s. It also proves that authors previously thought to be unimportant to Newton's late alchemical writings, such as Robert Boyle, played a larger role than once recognised. Finally, Newton's use of a text received from Fatio de Duillier for the later versions of the Index Chemicus suggests that the final versions may have been the product of a collaboration between the two.