Assisted reproductive technologies offer couples who cannot conceive naturally an important chance at parenthood. However, completing a fertility treatment successfully can be a physically and emotionally demanding journey.

Embryo quality is one of the key milestones along this journey. Understanding how embryos are graded can make the process easier and even encouraging.

“You deserve to be heard, seen, treated with respect, and supported throughout your life.”

If You Have Day 3 Embryos

After egg retrieval and laboratory fertilization, day 3 is the first major evaluation point for your embryos. In some cases, a day-3 transfer is performed at this stage.

What exactly are day-3 embryos? At this stage, the cells divide but do not grow in size, remaining roughly the size of an unfertilized egg. On day 3, the embryologist examines the embryo’s morphology under a high-power microscope, focusing primarily on the number and appearance of the cells.

An embryo developing normally ideally has between 6 and 10 cells, with 8 being optimal. Research shows that day-3 embryos with 8 or more cells have notably higher live-birth rates.

However, not all good-quality embryos follow the rules. Some may have 3, 5, or 6 cells because cell division is not always synchronized.

While counting the cells is straightforward, evaluating their appearance is more difficult, especially if the embryo cannot be viewed straight on. Day-3 embryos are graded from 1 to 4 (or 5), depending on lab protocol, with grade 1 being the highest.

What does the embryologist look for?

• Each cell should have a nucleus
• Cells should be similar in size
• Fragmentation: up to 20% is acceptable; higher levels may compromise cell function due to cytoplasm loss

If You Have Day 5 Embryos

Some fertility clinics prefer transferring embryos on day 5, when they reach about 80 cells and are known as blastocysts. At this stage, the embryologist can better evaluate two key structures:

• The inner cell mass (ICM) — which forms the fetus
• The trophectoderm — which forms the placenta; a normal trophectoderm is essential for ongoing development

Blastocyst grading is complex and typically combines a number grade (1–6) with letters (A, B, or C), where A indicates the highest quality. Importantly, these grades can change from one day to the next. A blastocyst graded C may later progress to an A, and blastocoel expansion may move from grade 1 to 6 within 24 hours.

Studies show that higher-graded blastocysts are associated with better pregnancy and live-birth outcomes, while lower-graded ones show lower rates — but not in all cases. Grading cannot predict success with certainty, and hope should never be lost based solely on these scores. însă nu întotdeauna. Notele nu pot prezice cu certitudine succesul unei sarcini, iar speranța trebuie menținută indiferent de scorul obținut.

Contact me

Talk with me about
Embryo Grading

If you have questions related to embryo grading or would like recommendations on evaluating and monitoring your newborn during the first days of life, you may request an individual consultation at any time. A thorough assessment helps determine the most suitable monitoring and support plan for your child.

Talk with me now