From the Guidelines
From 7 eggs retrieved, you can expect approximately 1-2 PGT-normal embryos by day 5. The progression typically follows a pattern of attrition: about 70-80% of eggs may fertilize (5-6 embryos), then about 40-50% of those might develop to blastocyst stage by day 5 (2-3 embryos), and finally about 40-60% of blastocysts may be chromosomally normal after PGT testing (1-2 embryos) 1. These numbers are influenced by several factors including maternal age, which is the strongest predictor of embryo euploidy rates. Women under 35 generally have higher rates of normal embryos (50-60%) compared to women over 40 (20-30%). Other factors affecting these outcomes include egg quality, sperm quality, laboratory conditions, and individual health factors.
Key factors to consider in this process include:
- Ovarian stimulation protocols, which can impact the number of eggs retrieved and subsequent embryos available for testing 1.
- The use of a GnRH antagonist protocol for high responders to ovarian stimulation, as recommended in the Chinese experts' consensus guideline on preimplantation genetic testing of monogenic disorders 1.
- The importance of patient education on the risks and potential outcomes of PGT-M, including the possibility of a low number of oocytes being retrieved or no transferable embryos 1.
The clinical process of PGT-M is the same as that of routine IVF-embryo transfer (IVF-ET), with the goal of obtaining more embryos for genetic testing and transfer in the PGT cycle 1. By understanding these factors and the typical attrition rate, reproductive endocrinologists can better counsel patients and optimize treatment strategies to increase the chances of having normal embryos available for transfer.
From the Research
Expected Embryo Yield at Day 5 with PGT Normal
- The number of embryos expected at day 5 with PGT normal cannot be directly determined from the provided studies, as they do not report on the specific relationship between the number of eggs retrieved and the number of embryos at day 5 with PGT normal.
- However, study 2 reports on the performance of preimplantation genetic testing for aneuploidy in IVF cycles for patients with advanced maternal age, repeat implantation failure, and idiopathic recurrent miscarriage, and found consistent live birth rates across different indications.
- Study 3 compares the effectiveness and cost of in-vitro fertilization with or without preimplantation genetic testing for aneuploidy when only one or two blastocysts are obtained, and found that PGT-A reduces the number of embryo transfers and miscarriages while the cumulative live birth rate per patient remains unaffected.
- Study 4 reports on the reproductive potential of embryos that achieve blastulation on day 7 followed by preimplantation genetic testing for aneuploidies, and found that day 7 embryos resulted in lower implantation and live birth rates compared to day 5 and day 6 embryos.
- Study 5 compares the effectiveness of two protocols of blastocyst biopsy submitted to preimplantation genetic testing for aneuploidies, and found that the new biopsy method exhibits advantages over the day-3 hatching-based TE biopsy method.
- Study 6 investigates the impact of preimplantation genetic testing on obstetric and neonatal outcomes, and found that PGT pregnancies had lower rates of low birth weight, very low birth weight, and very preterm births compared to IVF/ICSI pregnancies.
Factors Affecting Embryo Yield
- Maternal age: Study 2 found that PGT-A improves live birth rates in IVF cycles for patients with advanced maternal age.
- Number of eggs retrieved: While not directly reported in the studies, the number of eggs retrieved is likely to affect the number of embryos available for PGT testing.
- Embryo development: Study 4 found that embryos that achieve blastulation on day 7 have reduced implantation potential compared to day 5 and day 6 embryos.
- PGT-A protocol: Study 5 found that the new biopsy method exhibits advantages over the day-3 hatching-based TE biopsy method.