Embryo Quality & Grading – Does It Affect IVF Success?

By BSc, MSc (senior clinical embryologist), BSc, MSc, PhD (senior clinical embryologist), MD, FACOG, FACS, FACE (reproductive endocrinologist), BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 03/31/2014

With the exception of artificial insemination, fertilisation occurs outside the female body in most assisted reproductive techniques and later embryo transfer is performed.

For selective embryo transfer, specialists rely on a series of criteria which help determining the quality of the embryos.

While embryos are being cultured, their quality is microscopically assessed. Embryo quality assessment implies analysing both embryo morphology and embryonic development.

Understanding embryo grading

Grade I

Cells or blastomeres are of equal size and no fragmentation is seen. Their texture is uniform and they are light-coloured. There is no evidence of multinuclear blastomeres (more than one nucleus per cell).

Grade I

Grade II

Minor fragmentation only (less than 15% of the embryo) and/or cells are mostly of equal size.

Grade II

Grade III

The fragmentation rate is 10-40% of the embryo. Blastomeres are of unequal size and/or their surface is less smooth.

Grade III

Grade IV

The fragmentation rate is higher than 40%. Cells are now dark-coloured and less smooth.

Grade IV

Grade V

Fragmentation is heavy and the embryo is dark-coloured.

Grade V

Factors examined

As regards embryo morphology, the following aspects are taken into account: the zona pellucida thickness, the cytoplasmic vacuoles, the adhesion between blastomeres and the presence of a cytoplasmic filament.

If the zona pellucida is especially thick, embryo transfer can be performed previously to the assisted zona hatching (AZH) technique, a.k.a. assisted hatching (AH). AZH may facilitate the inner cell mass to break through the zona pellucida.

Zona pellucida

Embryonic development is another marker for embryo quality assessment.

This criterion can be summarised as follows: the greatest number of cells, the greater probability of implantation into the maternal uterus, always respecting the maximum of 4 cells two days after fertilisation and 8 cells for 3-day embryos.

Embryos with a cleavage faster than normal are considered as poor quality embryos, since they are more likely to develop a genetic alteration, usually aneuploidy.

Conclusions

Grade I and grade II embryos are considered good quality embryos.

Conversely, grade III embryos are considered as moderate quality embryos, although there are still chances for pregnancy. Embryo quality is related to embryonic development and embryo–endometrial linkage capacity. However, grade III embryos are not necessarily associated with a genetic alteration. Grade IV embryos present a poorer prognosis.

Grade V embryos are not transferred to the maternal uterus. They are cultured while their progress is monitored. Nevertheless, practically overall majority of grade V embryos do not continue its development. Their poor development may indicate that they are non-viable.

FAQs from users

What causes poor quality embryos?

By Mark P. Trolice MD, FACOG, FACS, FACE (reproductive endocrinologist).

This is a very common question but not an easy answer. First, the term “quality” is not well defined in reproductive medicine: is it based on appearance of the embryo?; is it the chromosomal competence of the embryo; or the structrual/genetic make-up? The first two metrics are definable – we can grade an embryo base on appearance; we can test the embryo for the chromosomal content. Neither of these qualifiers correlate well with the ability for the embryo to result in a live birth. Structural/genetic make-up is not able to be tested at this time.

Traditionally, we have considered a woman’s age as the dominant forcé contributing to egg “quality.” The percentage of chromosomally abnormal embryos increase as the woman ages. While male fertility declines with age, we do not have as much information on their contributions to embryo quality.

Can you pregnant with C and D scored embryos?

By José Muñoz Ramírez BSc, MSc, PhD (senior clinical embryologist).

Yes, although the chances are quite low.

When we classify embryos according to their quality at the lab, we do so by evaluating their implantation potential, that is, trying to "guess" which ones have greater chances for attaching tot he uterus, and which don't. C and D scored embryos are embryos of moderate-to-low quality, which means that a C or D scored embryo has a reduced chance of implantation if compared to a B or A scored embryo. In any case, however, whenever we select an embryo for the transfer, it's because it has been observed that its implantation potential is a good one.

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.

References

Authors and contributors

 Edurne Martínez Sanz
Edurne Martínez Sanz
BSc, MSc
Senior Clinical Embryologist
Bachelor's Degree in Biochemistry from the University of Navarra and Master's Degree in Biotechnology from the Valencian Infertility Institute (IVI) and the University of Valencia (UV). More than 10 years' experience working as an embryologist for several fertility clinics, including IVI, Grupo Hospitalario Quirónsalud, and currently, Reproducción Bilbao. More information about Edurne Martínez Sanz
 José Muñoz Ramírez
José Muñoz Ramírez
BSc, MSc, PhD
Senior Clinical Embryologist
Bachelor's Degree in Biology from the University of Malaga. Master's Degree in Genetics by the University of Alcalá, and Master's Degree in Assisted Reproduction from the University of Valencia. He works as a clinical embryologist at Clínica Tambre (Madrid, Spain), in addition to being an Associate Professor at the University of Murcia. More information about José Muñoz Ramírez
 Mark P. Trolice
Mark P. Trolice
MD, FACOG, FACS, FACE
Reproductive Endocrinologist
Mark P. Trolice is the Director of Fertility CARE – The IVF Center and Clinical Associate Professor in the Department of Obstetrics & Gynecology (OB/GYN) at the University of Central Florida College of Medicine. He is Board-certified in REI and OB/GYN, and maintains annual recertification. His colleagues select him as Top Doctor in America® annually, one among the top 5% of doctors in the U.S. More information about Mark P. Trolice
License: ME 78893
 Neus Ferrando Gilabert
Neus Ferrando Gilabert
BSc, MSc
Embryologist
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information about Neus Ferrando Gilabert
Adapted into english by:
 Sandra Fernández
Sandra Fernández
BA, MA
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

Find the latest news on assisted reproduction in our channels.