Model predicts number of MII oocytes needed to obtain at least one euploid blastocyst: Study
Female age is significantly and directly related to embryo
aneuploidy rates. The current delay in motherhood has led to a large proportion
of women of advanced maternal age seeking infertility treatment, thus
presenting significantly higher embryo aneuploidy rates. Consequently, these
patients are characterized by lower chances of success in in vitro
fertilization (IVF) treatments with their own oocytes and many of them are
finally encouraged to enter the oocyte donation program.
In the assumption of the statement ‘‘the older the patient,
the lower the number of euploid blastocysts,’’ there is a frequently asked
question in the day-to-day operations of an infertility clinic: how many
oocytes each of our patients’ needs, according to female age, to have the
highest chances of obtaining at least one euploid blastocyst in their IVF
treatment cycles? The answer to this question would constitute useful
information for both the clinician and the patient. On the one hand, the
clinician may be able to better assess each patient’s possibilities and the
feasibility of their treatment cycle because it will be easier to explain the
patient’s options. On the other hand, the patient will understand this
information more easily, helping her to cope emotionally with treatment. This
is nowadays feasible because predicting ovarian response with high precision
before starting treatment has become possible with the use of novel biomarkers,
such as antimullerian hormone levels and/or antral follicle count.
The aim of the present study by Cristina Rodríguez-Varela et
al was to design a similar tool to determine the number of metaphase II (MII)
oocytes needed to obtain at least one euploid blastocyst regarding female age
in IVF treatment cycles, considering our own data from the last 5 years using
next-generation sequencing (NGS) on TE biopsies. This information will help to decide
the best strategy for each patient and her individual situation.
Eligible patients were undergoing their first IVF-PGT-A
treatment cycle, in which at least one MII oocyte was obtained, regardless of
oocyte and semen origin. Oocyte donation cycles were included in the donor
group (≤34
years old). Treatment cycles from women with their own oocytes were selected only
when the oocytes were aged ≥35 years (patient group). Only
trophoectoderm biopsies performed on days 5 or 6 of development and analyzed using
next-generation sequencing were included. Preimplantational genetic testing for
aneuploidy cycles because of a known abnormal karyotype were excluded.
A total of 2,660 IVF-PGT-A treatment cycles were performed
in the study period in the eligible population (patients group = 2,462; donors
group =198). The mean number of MII oocytes needed to obtain one euploid
blastocyst increased with age, as did the number of treatment cycles that did
not get at least one euploid blastocyst. An adjusted multivariate binary
regression model was designed using 80% of the patient group sample (n = 2,462;
training set). A calculator for the probability of obtaining at least one
euploid blastocyst was created using this model. The validation of this model
in the remaining 20% of the patient group sample (n = 493; validation set)
showed that it could estimate the event of having at least one euploid
blastocyst with an accuracy of 72.0%
The minimum number of MII oocytes needed to have high
chances of obtaining at least one euploid blastocyst increases with increasing
maternal age. Study model estimates with an accuracy of 74% the probability of
having at least one euploid blastocyst, considering oocyte age and the number
of MII oocytes. This model has been created with the largest database of
IVF-PGT-A treatment cycles ever used for this purpose, including only PGT-A
treatment cycles using NGS on TE biopsies. Once this model has been validated
prospectively and in multicenter studies, it may be useful for both the
clinician and the patient coming to an infertility clinic, whether or not a
PGT-A analysis is performed. The clinician may use this data to propose the
best strategy for each patient, whereas the patient may use this information to
better understand the likelihood of obtaining an euploid blastocyst, helping
her to cope emotionally with IVF treatment. Nevertheless, to this day, this
model has limited clinical value. It should be further validated and optimized
to use it as a clinical support tool, in our own clinic and in many others.
Source: Cristina Rodríguez-Varela, M.Sc.,a Juan Manuel
Mascaros, M.Sc., a Elena Labarta; Fertil
Steril® Vol. 122, No. 4, October 2024
