Research questionDoes complete resection of endometriosis improve embryo quality as assessed by morphokinetic parameters using time-lapse microscopy?DesignFor this retrospective study we analysed 237 fertilised, cultured and transferred embryos from 128 fresh IVF and/ or ICSI transfer cycles. Endometriosis was confirmed or excluded by laparoscopy. Patients were stimulated with recombinant FSH using GnRH agonist and antagonist protocols. After fertilisation, a time-lapse incubation system was used for observation. Embryo quality was assessed using the KIDScore™ D3 and D5 implantation data algorithm.ResultsThe analysis showed a median KIDScore™ D5 of 2.6 (on a scale of 1 to 9.9) for embryos from patients with endometriosis without complete resection. The control group without endometriosis achieved a score of 6.8 (p= 0.003). The median score for embryos from endometriosis patients with complete resection was 7.2, which was a significant increase compared to embryos from patients without complete resection (p= 0.002). We observed an effect size ofr= 0.4 for complete resection versus no resection of endometriosis using the KIDScore™ D5. There were no differences in KIDScore™ D3 between the three patient groups. Pregnancy and miscarriage rates showed the same clinical trends. In three of our four case series of patients who underwent IVF/ ICSI cycles before and after complete resection, we found a marked improvement in embryo quality after complete resection.ConclusionsComplete resection of endometriosis could significantly improve the otherwise poor embryo quality of patients undergoing IVF-procedures. The data, therefore, strongly support recommending surgery to patients with endometriosis prior to assisted reproduction.