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STUDY QUESTION In oocytes of advanced maternal age (AMA) women, what are the mechanisms leading to aneuploidy and what is the association of aneuploidy with embryo development? SUMMARY ANSWER Known chromosome segregation errors such as precocious separation of sister chromatids explained 90.4% of abnormal chromosome copy numbers in polar bodies (PBs), underlying impaired embryo development. WHAT IS KNOWN ALREADY Meiotic chromosomal aneuploidies in oocytes correlate with AMA (>35 years) and can affect over half of oocytes in this age group. This underlies the rationale for PB biopsy as a form of early preimplantation genetic testing for aneuploidy (PGT-A), as performed in the 'ESHRE STudy into the Evaluation of oocyte Euploidy by Microarray analysis' (ESTEEM) randomized controlled trial (RCT). So far, chromosome analysis of oocytes and PBs has shown that precocious separation of sister chromatids (PSSC), Meiosis II (MII) non-disjunction (ND), and reverse segregation (RS) are the main mechanisms leading to aneuploidy in oocytes. STUDY DESIGN, SIZE, DURATION Data were sourced from the ESTEEM study, a multicentre RCT from seven European centres to assess the clinical utility of PGT-A on PBs using array comparative genomic hybridization (aCGH) in patients of AMA (36–40 years). This included data on the chromosome complement in PB pairs (PGT-A group), and on embryo morphology in a subset of embryos, up to Day 6 post-insemination, from both the intervention (PB biopsy and PGT-A) and control groups. PARTICIPANTS/MATERIALS, SETTING, METHODS ESTEEM recruited 396 AMA patients: 205 in the intervention group and 191 in the control group. Complete genetic data from 693 PB pairs were analysed. Additionally, the morphology from 1034 embryos generated from fertilized oocytes (two pronuclei) in the PB biopsy group and 1082 in the control group were used for statistical analysis. MAIN RESULTS AND THE ROLE OF CHANCE Overall, 461/693 PB pairs showed abnormal segregation in 1162/10 810 chromosomes. The main observed abnormal segregations were compatible with PSSC in Meiosis I (MI) (n = 568/1162; 48.9%), ND of chromatids in MII or RS (n = 417/1162; 35.9%), and less frequently ND in MI (n = 65/1162; 5.6%). For 112 chromosomes (112/1162; 9.6%), we observed a chromosome copy number in the first PB (PB1) and second PB (PB2) that is not explained by any of the known mechanisms causing aneuploidy in oocytes. We observed that embryos in the PGT-A arm of the RCT did not have a significantly different morphology between 2 and 6 days post-insemination compared to the control group, indicating that PB biopsy did not affect embryo quality. Following age-adjusted multilevel mixed-effect ordinal logistic regression models performed for each embryo evaluation day, aneuploidy was associated with a decrease in embryo quality on Day 3 (adjusted odds ratio (aOR) 0.62, 95% CI 0.43–0.90), Day 4 (aOR 0.15, 95% CI 0.06–0.39), and Day 5 (aOR 0.28, 95% CI 0.14–0.58). LIMITATIONS, REASON FOR CAUTION RS cannot be distinguished from normal segregation or MII ND using aCGH. The observed segregations were based on the detected copy number of PB1 and PB2 only and were not confirmed by the analysis of embryos. The embryo morphology assessment was static and single observer. WIDER IMPLICATIONS OF THE FINDINGS Our finding of frequent unexplained chromosome copy numbers in PBs indicates that our knowledge of the mechanisms causing aneuploidy in oocytes is incomplete. It challenges the dogma that aneuploidy in oocytes is exclusively caused by mis-segregation of chromosomes during MI and MII. STUDY FUNDING/COMPETING INTEREST(S) Data were mined from a study funded by ESHRE. Illumina provided microarrays and other consumables necessary for aCGH testing of PBs. None of the authors have competing interests. TRIAL REGISTRATION NUMBER Data were mined from the ESTEEM study (ClinicalTrials.gov Identifier NCT01532284). [ABSTRACT FROM AUTHOR]

It is essential to deposit embryos as gently as possible during IVF, avoiding manoeuvres that might trigger uterine contractions which could adversely affect the results of this treatment. The time during which the embryo transfer catheter remains in the cervical canal might be related to stimulation of contractions. This study investigates the influence that the time interval before withdrawal of the catheter after ultrasound (US)-guided embryo deposit might have on the pregnancy rate in patients under IVF cycles. A total of 100 women about to undergo transfer of at least two optimal embryos was studied. The women were prospectively randomized into two groups: (i) slow withdrawal of the catheter immediately after embryo deposit (n = 51); and (ii) a 30 s delay before catheter withdrawal (n = 49). The pregnancy rates for transfer in the two groups were 60.8 and 69.4% respectively, with no significant differences. There were no statistically significant differences in pregnancy rates between the two patient groups. The results indicate either that the waiting interval was insufficient to detect differences, or that the retention time before withdrawing the catheter is not a factor that influences pregnancy rate. [ABSTRACT FROM AUTHOR]