O-184 Validation of a model capable of estimating the minimum number of mature oocytes needed to obtain at least one euploid blastocyst regarding female age
Authors: Rodríguez Varela C , Labarta E , Mascarós J M , Bosch E 
Published: June 2023

Abstract

Study question
Which is the minimum number of mature oocytes needed to obtain at least one euploid blastocyst regarding female age in In Vitro Fertilization (IVF) treatments?

Summary answer
The validated model estimates with a 74% accuracy the probability of having one euploid blastocyst regarding the number of mature oocytes and female age.

What is known already
Female age is significantly and directly related to embryo aneuploidy rates, thus lowering the chances of success in IVF treatments. The current delay in motherhood has led to a large proportion of women of advanced maternal age seeking infertility treatment. The aim of the present study is to determine the number of metaphase II (MII) oocytes needed to obtain at least one euploid blastocyst regarding female age. This information will help to decide the best strategy for each patient, taking also into account other variables such as ovarian reserve, semen quality and oocyte quality.

Study design, size, duration
Retrospective analysis of IVF cycles with pre-implantational genetic testing for aneuploidies (PGT-A) performed over the last 5 years in an infertility clinic in Spain, from January 2017 to March 2022.

Participants/materials, setting, methods
Patients undergoing an IVF cycle in an infertility clinic with own or donated oocytes, regardless semen origin. Only trophoectoderm biopsies performed on day 5 or 6 of development and analyzed using Next Generation Sequencing (NGS) were included. PGT-A was used for reasons such as advanced maternal age, implantation failure and recurrent miscarriage. PGT-A cycles due to a known abnormal karyotype were excluded. Endpoints were analized using binary logistic regression models.

Main results and the role of chance
A total of 3840 IVF-PGT-A cycles meeting the inclusion criteria were performed in the study period. Of them, 939 cycles were discarded due to the absence of any biopsied/analyzed embryo (final sample size=2901). A model for the probability of having at least one euploid blastocyst (pEB) regarding female age and the number of MII oocytes retrieved was created with 80% of the sample (n = 2320) and validated in the remaining 20% (n = 581). The validation of this model showed that it was capable of estimate with an accuracy of 73.88%. The pEB was directly related to the number of MII oocytes retrieved (odds ratio (OR) 1.130, confidence interval (IC) 95% (1.110-1.150); p &lt; 0.001), but indirectly related to female age (OR 0.751, IC95% (0.725-0.778); p &lt; 0.001). The ROC curve showed a significant predictive value of the number of MII oocytes (area under the curve (AUC):0.8041 (0.7882-0.82)) for this model. A mathematical formula was created for the calculation of pEB using this model. The number of MII oocytes needed for a pEB of 75% regarding female age (female age:number MII) was 35:6, 36:9, 37:12, 38:15, 39:18, 40:21, 41:24, 42:27, 43:30, 44:32, 45:35, 46:38, 47:41, 48:44, 49:47, 50:50.

Limitations, reasons for caution
The main limitation of this study is its retrospective design. In addition, it’s important to keep in mind that many other variables should be taken into consideration along with maternal age in the assessment of the number of oocytes needed to obtain at least one euploid blastocyst in IVF treatments.

Wider implications of the findings
Results from this study may constitute a useful tool for both clinical and patient. The clinician may be able to better decide the best strategy for each patient, while the patient will understand more easily this information, helping her morally with the treatment.

Trial registration number
2204-VLC-040-CR