Choosing the best embryo is one of the major challenges for achieving success in in vitro fertilization (IVF). Traditionally, embryo evaluation has been based on morphological quality (how the embryo looks like) and chromosomal status as diagnosed by a genetic testing. However, recently new techniques that do not require manipulation of the embryo have been developed and have shown promising results.

The goal of this observational study is, by combining two non-invasive techniques, to find out some parameters during embryo development which may be related with the embryo's chromosomic status. For that, infertile women planning to undergo an IVF/ICSI treatment with a recommended niPGT-A (non-invasive Preimplantation Genetic Testing for Aneuploidies) will be invited to join the study. The main question it aims to answer is:

• Can morphokinetics parameters correlate with embryo chromosomal status?

Participants will follow their previously programmed IVF/ICSI treatment and no additional visits/interventions will be required by their participation in the study. The obtained embryos will be cultured in a time-lapse system instead of in a conventional incubator, and niPGT-A will be performed. Following the standard practice, a deferred single embryo transfer (SET) will be performed according to the niPGT-A results. After the transfer, patients will be followed-up as usual.

Embryo selection represents one of the major challenges for achieving success in in vitro fertilization (IVF) cycles. Traditionally, embryo evaluation has been based on morphological quality and chromosomal status as diagnosed by a genetic testing. However, recently new non-invasive techniques that do not require additional manipulation of the embryo have been developed and have shown promising results. One such technique is the time-lapse (TL) system imaging, which considers the embryo's development in relation to its rate of division and evolution (morphokinetics). Several algorithms have been developed to aid in the selection of embryos with the highest potential for implantation by collecting data on morphokinetic events during in vitro preimplantation development. Another non-invasive method is the analysis of the cell-free desoxyribonucleic acid (cfDNA) in the culture medium, considered as a non-invasive preimplantation genetic testing for aneuploidies (niPGT-A). Despite both techniques have shown promising results, each one has its limitations, and further research is necessary to identify synergies between them with the aim of finding a more powerful approach for embryo viability evaluation.

The combination of TL and niPGT-A might have the potential to improve the embryo evaluation and thus to improve the reproductive outcome rates in IVF treatments. Therefore, the aim of the present pilot study is to identify morphokinetic parameters during embryo development in a time-lapse system which may correlate with niPGT-A results.

Once the study is approved by the competent Research Ethics Committee of each center, the recruitment and selection of patients will follow. Every potential participant will be asked to sign the study informed consent. To comply with the study design and the proposed hypothesis, an estimated total number of 200 patients will be recruited.

This is a multicenter, international, competitive, observational, prospective cohort study in which infertile women scheduled for an IVF/ICSI treatment with medical recommendation of niPGT-A will have their embryos cultured in a time-lapse system instead of in a standard incubator. On day 6/7 of embryo development, the embryo's culture medium will be collected and analyzed by niPGT-A. A subsequent embryo transfer will be performed following the niPGT-A report recommendation and participants will be followed up as routine by their gynecologist. If a pregnancy is achieved, participants will be followed up until the 12th gestational week and, if possible, until the delivery. If pregnancy is not achieved, patients can perform as many SET/COS as they need during the study recruitment period.

Data exported from the medical records and source documents will be duly codified to protect the clinical and personal information of patients in accordance with the current legislation on data protection. This information will be exported to an internal database. An interim data analysis will be carried out once the 50% of the niPGT-A cycles (100 cycles) is reached. It will help us to assess the enrollment rate, protocol compliance and an early evaluation of the study objectives.

Patient´s participation will comprise an estimated total time of up to 11 months: 1 month for the COS cycle + 1 month for the ET cycle + ≤ 9 months for the follow-up period (≤12th gestational week and ≤ 40th gestational week, when applicable).

Inclusion Criteria:

• Study ICF signature.
• Female age between 20 and 42 years (bot included).
• IVF, ICSI or IVF/ICSI performed in fresh own or donated oocytes. Note: donor sperm is allowed.
• niPGT-A cases with a deferred SET (of a day 6/7 vitrified blastocyst) for any medical indication.
• Embryos cultured individually in a TL system from day 0/1 to day 6/7.

Exclusion Criteria:

• Embryos with abnormal fertilization (different from 2PN). (Note: In case of no 2PN embryos, patients may repeat the COS cycle).
• Female/couple with PGT-M and/or PGT-SR indication.
• Assisted hatching and/or artificial collapse before media collection.
• Known abnormal karyotype.
• Pathologies or malformations affecting the uterine cavity (polyps, intramural myomas ≥ 4cm or submucosal, septum or hydrosalpinx) during the patient's participation. (Note: patients are allowed to participate if the pathology is previously operated at least 3 months before patient enrollment).
• Any illness or medical condition that is unstable or which, according to medical criteria, may put at risk the patient's safety and her compliance in the study.

Infertile women complying with the selection criteria who are patients at an assisted reproduction center and, by medical recommendation, are undergoing a fertility treatment with non-invasive preimplantational genetic testing for aneuploidies.