While removal of two blastomeres decreases the likelihood of blastocyst formation, compared with removal of one blastomere, Day 3 in vitro developmental stage is a stronger predictor for Day 5 developmental potential than the removal of one or two cells. The biopsy of only one cell significantly lowers the efficiency of a PCR-based diagnosis, whereas the efficiency of the FISH PGD procedure remains similar whether one or two cells are removed. Delivery rates with live birth per started cycle were not significantly different.

The early OHSS pattern is associated with exogenously administered HCG and a higher risk of preclinical miscarriage, whereas late OHSS may be closely associated with the conception cycles, especially multiple pregnancies, and is more likely to be severe. Further clarification of these two different clinical entities could have implications for research protocols as well as for preventive and management strategies for OHSS.

The absence of a beneficial treatment effect in this randomized clinical trial provides no arguments in favour of PGS to improve live birth delivery rate following single-embryo transfer in women under the age 36. Clinical Trials.gov: NCT00670059.