P-231 How many blastocysts are necessary to reach pregnancy with preimplantation genetic testing?
Authors: Badalotti M , Badalotti-Teloken I , Wingert F  M , Vasconcelos N  F , Hentschke M  R , Trindade V  D , Arent A  C , Azambuja R , Dornelles V  C , Petracco A 
Published: July 2024

Abstract

Study question
What is the influence of the number of blastocysts before biopsy on the prognosis of pregnancy in preimplantation genetic testing for aneuploidy (PGT-A) cycles?

Summary answer
The number of pre-biopsy blastocysts seems to be a parameter that can be used as a prognostic factor for the pregnancy chance in PGT-A cycles.

What is known already
Advances in embryo cryopreservation techniques have allowed for a greater use of PGT. Studies showed that PGT-A has improved live birth rates while reducing the number of embryos transferred. There is a lot of information about the role of the oocyte number as a predicting factor for pregnancy rate. However, little information is available about the influence of the number of blastocysts before performing PGT-A on the chance of achieving a pregnancy.

Study design, size, duration
Retrospective study performed in a reproductive medicine center using the first IVF cycle from 2016 to 2023, including 682 patients with at least one blastocyst before undergoing PGT-A. All patients performed a single embryo transfer in each procedure, in up to 4 transfers.

Participants/materials, setting, methods
The sample was divided into four groups according to the blastocyst number: G1, 1 to 2 blastocysts (n = 324); G2, 3 to 4 (n = 197); G3, 5 to 9 (n = 137); and G4, ≥ 10 blastocysts (n = 24); each group was divided according to female age (≤ 37 and &gt; 37) Variables: female age, and euploidy, clinical pregnancy per transfer and cumulative clinical pregnancy rates. Data were compared between groups. Statistical analysis: Chi-square test (Bonferroni correction) and Anova (p &lt; 0.05).

Main results and the role of chance
The results in G1, G2, G3 and G4 were, respectively: female age, yo (40 vs. 38.4 vs. 37.2 vs. 34.7, p &lt; 0.01); euploidy rate (34.6 vs. 67.2 vs. 83.2 vs. 100.0, p &lt; 0.0001), clinical pregnancy rate per transfer, % (45.5 vs. 58.6 vs. 72.8 vs. 95.8 p &lt; 0.0001 ), cumulative clinical pregnancy rate, % (15,7 vs. 39.4 vs. 60.6 vs. 95,8% p &lt; 0.0001). Women with 1 to 2 blastocysts before biopsy had a cumulative pregnancy rate more than 3-fold lower than those with 3 to 4 blastocysts (%, 39.6 vs. 15.3, p &lt; 0.001, OR 3.59, CI 95% 2.32 to 5.57) and more than 8-fold lower than those with 5 to 9 blastocysts (%, 60,6 vs. 15.3, p &lt; 0.001, OR 8.42, CI 95%: 5.20 to 13.64). The comparison in each group according to female age showed that until 9 blastocysts, the younger women had a pregnancy rate higher than the older, respectively (%): G1: 30.8 vs. 12.5, p = 0.001; OR 3.1, CI 95%: 1.44 to 6.48; G2: 57.4 vs. 30.2, p &lt; 0.001; OR 3.10, CI 95%: 1.61 to 5.98; G3: 72.6 vs. 50.7, p = 0.009. OR 2.58; IC 95%: 1.19 to 5.67; and G4: 93.8 vs. 87.5, p = 0.268.

Limitations, reasons for caution
As a retrospective study, data collection and filling limitations should be considered.

Wider implications of the findings
The number of pre-biopsy blastocysts appears to be a parameter that can be used as a prognostic factor for the pregnancy chance in PGT-A cycles. Even transferring 1 embryo, the pregnancy rate/transfer was higher with more blastocysts. In patients with less than 10 blastocysts before PGT, age influences pregnancy rates.

Trial registration number
Not Applicable