It is normal that not every egg retrieved at egg collection will be mature, or be able to fertilise normally. After the eggs have been inseminated with sperm via In Vitro Fertilisation (IVF), or Intracytoplasmic Sperm Injection (ICSI), they are left uninterrupted and assessed the next day for signs of fertilisation.

The embryologist will observe each egg and look to identify the presence of pronuclei (PN). Pronuclei represent the presence of the genetic material (DNA) within the fertilised egg (zygote). A successfully fertilised egg will have two pronuclei (2PN), one from the egg, and one from the sperm. Some eggs may present with an abnormal number of pronuclei, containing too little (1PN), or too much (3PN+) DNA. Embryos resulting from abnormally fertilised eggs may have reduced pregnancy potential, or an increased risk of leading to miscarriage.
All normally fertilised eggs (2PN) will be kept and grown in the lab, while abnormally fertilised eggs will be discarded or monitored in the lab depending on the type of abnormality present.

The 2PN stage is an important milestone in embryonic development, as it signifies successful fertilisation and the potential for further embryonic development.

Embryo grading is an important part of the In Vitro Fertilization (IVF) process. The purpose of grading embryos is to determine the pregnancy potential of each embryo and determine whether they are suitale to be transferred back into the uterus, or frozen. Grading involves assessing the number of cells within each embryo, as well as the quality of these cells. It also takes into consideration each embryos ability to meet particular developmental milestones throughout its growth in the lab. Embryo grading is performed by a skilled embryologist using a grading system that assigns a grade or score to the embryos based on their physical characteristics.

There are a number of grading systems used to assess the quality of embryos in IVF, and the way in which the grade is communicated may vary depending on the clinic or laboratory. The most widely understood system is the Gardner grading system, which was developed by David Gardner and colleagues in the early 2000s.

The Gardner grading system assigns a grade to the embryos based on their appearance and development on days two, three, and five after fertilization. Here is a breakdown of the grading system:

Day 2:

• Grade 1: Four cells of equal size
• Grade 2: Four cells of slightly uneven size
• Grade 3: Four cells of significantly uneven size

Day 3:

• Grade 1: Eight cells of equal size
• Grade 2: Eight cells of slightly uneven size
• Grade 3: Eight cells of significantly uneven size

Day 5:

• Grade 1: Blastocyst with an expanded cavity and a well-defined inner cell mass and trophectoderm
• Grade 2: Blastocyst with a less expanded cavity and less defined inner cell mass and trophectoderm
• Grade 3: Blastocyst with a small cavity and poor inner cell mass and trophectoderm

The grade assigned to the embryo is based on the best score it receives on each day of assessment. For example, an embryo that receives a grade 1 on day two, a grade 2 on day three, and a grade 2 on day five would be assigned a final grade of 2.

The grading system is used to help embryologists select the best quality embryos for transfer back to the patient’s uterus. In general, embryos with higher grades have a better chance of implantation and a successful pregnancy. However, it is important to note that embryo grading is just one factor that is considered when selecting embryos for transfer, and other factors such as the patient’s age, medical history, and previous IVF outcomes are also taken into account.

If your embryo develops into a high-quality blastocyst on day 6, we will not perform an immediate embryo transfer. Instead, we will freeze the blastocyst because we want to place it back into the uterus on day 5 to account for its slower development. This gives the embryo the best chance for successful implantation.

No, it is not possible to perform rescue ICSI on the IVF eggs as we cannot confirm if a sperm has already entered the egg. Adding another sperm at this point could result in an abnormal embryo.

During your cycle, we monitored the growth of your follicles using ultrasound. Follicles over a certain size should contain mature eggs, and we collected the eggs when the follicles were deemed ready. Unfortunately, not all large follicles contain mature eggs. You can discuss this further with your specialist during a review appointment.

No, we cannot inject immature eggs as they do not have the potential to fertilize normally. A mature egg has undergone a maturation process where it removes half of its genetic material to make space for the DNA from the sperm. If an egg has not undergone this process, it will have too many chromosomes and will not result in a viable pregnancy.

It is difficult to determine why an embryo did not survive. When grading embryos for freezing, we assess them based on their development stage and the quality of the cells visible at the time of freezing. Although a good quality embryo should typically survive the freeze, this outcome could indicate that the embryo had abnormalities. However, each embryo can respond differently to the freezing/thawing process, so it does not necessarily mean that your other embryos will have the same outcome.

Day 3 and Day 5 embryos refer to the age of the embryo in vitro, meaning the number of days since fertilisation of the egg in a laboratory setting.

A Day 3 embryo, also referred to as a cleavage stage embryo, is typically a 6-12 cell structure.

By Day 5, an embryo will hopefully have undergone many cell divisions, having hundreds of cells, and now be referred to as a blastocyst. Blastocysts have an identifying fluid-filled cavity surrounded by a layer of cells. At this stage, the inner cell mass has formed and will eventually develop into the embryo, while the outer layer of cells will eventually form the placenta.

Not every embryo will reach the blastocyst stage, this is a normal and expected outcome of extended embryo culture. Some embryos will arrest in development which will help deselect against the poorer quality embryos lacking the potential for pregnancy.

In summary, the main difference between a Day 3 and Day 5 embryo is the degree of development and differentiation of the cells.

In order to be suitable to freeze, an embryo must meet standardised criteria which has been set to ensure only embryos with the potential for pregnancy are stored for future use.

Embryos need to have reached set developmental milestones, as well have a suitable embryo grade. Poor quality embryos, such as those that have poor cell division, do not have the potential to lead to a viable pregnancy. They are also less likely to survive the freezing and thawing process and are therefore not suitable for storage.

It is important to note that not all embryos are suitable for freezing and that the quality of the embryo at freezing may affect how well the embryo survives the thawing process. Typically, it is expected that 90-95% of frozen blastocysts will survive the process.

IVF (In Vitro Fertilization) and ICSI (Intracytoplasmic Sperm Injection) are two assisted reproductive technologies (ARTs) used to treat infertility. The only differences between the two, is the method of insemination used.

IVF is a process where the retrieved eggs are added to a prepared sperm sample in a laboratory dish. The sperm and eggs are then left together whereby the sperm is required to find and fertilise each egg naturally.

ICSI on the other hand, is a more invasive procedure where a single sperm is injected directly into each mature egg. ICSI is typically used in cases of male infertility, where the sperm has difficulty reaching and fertilising the egg on its own, or in cases of previous failed fertilisation using IVF.

IVF with MIRI is a type of assisted reproductive technology (ART) where the fertilised eggs are monitored in a specialised incubator (MIRI) that provides constant time-lapse imaging. This allows embryologists to closely observe the development of embryos in real-time, increasing the chances of successful implantation and pregnancy.

UTM is a substance used in some IVF cycles to help the embryo attach to the uterine wall more effectively. It is a type of growth factor and is applied to the embryos before they are transferred to the uterus.

No, our clinic does not currently offer PGD/PGT-A testing. However, we can recommend clinics that offer these services for those who require them. We hope to provide this service in the near future.

All women of reproductive age have some abnormal eggs, which increase with age.