Pregnancy Outcomes with IVF and ICSI: An Embryologist Explains

Pregnancy Outcomes

“Pregnancy Outcomes with IVF and ICSI: An Embryologist Explains” Guest post by Kristen Jones, Embryologist

The decision to move on to the next phase of fertility treatments is a big one. There are so many factors to consider when thinking about In Vitro Fertilization (IVF) – emotional stability, finances, timeline, and current health status are just some of them. There are also many steps involved in IVF that require a basic understanding of the process in order to make the best decisions for you.

One of those decisions is whether to have Intracytoplasmic Sperm Injection (ICSI).

fruit and vegetables that look like sperm and an egg

To ICSI or not to ICSI?

 In an IVF cycle, you may hear your doctors referring to IVF and ICSI. While it may result in differences in fertilization rates (more on that below), it makes no difference to your stimulation or your cycle, and it is simply how the eggs are going to be inseminated. Your cycle will still start with controlled ovarian stimulation, monitoring, and then trigger injection, followed by your egg collection. After egg collection, the eggs need to meet with the sperm, and this needs to happen either with the assistance of ICSI, or just by placing the eggs and sperm in a petri dish together.

With IVF, a measured concentration of washed sperm is placed together with the eggs. This is the more natural, less invasive way, as the eggs are not manipulated.

Your doctor may be happy for you to proceed in this manner if:
  • There is a history of natural pregnancies in the past
  • Sperm quality is good
  • You have not had poor or failed fertilization in the past

The other option is ICSI, which stands for Intracytoplasmic Sperm Injection.  It is a process in which the eggs are stripped of their fluffy cumulus cells and examined for the presence of a polar body. Anything with a polar body is a mature egg and can be injected with a single sperm. As with IVF without ICSI, the eggs are checked for signs of fertilization the morning after egg retrieval. It is generally deemed a good result if at least 50% of the eggs have been fertilized.  This is the same rate of fertilization we would expect in the case where ICSI is not deemed necessary.  Patients that have had a previously unsuccessful round of IVF may get better results with ICSI.

a bee fertilizing a flower

Your doctor may suggest ICSI if you have:
  • A history of poor fertilization
  • Very poor sperm count or motility
  • High DNA fragmentation
  • Particular types of genetic testing done

So, is one better than the other? All things being equal, no. Statistically, success rates with IVF and ICSI are comparable and it’s up to your individual circumstances and your doctor to decide what is better for you.

improving egg quality ivf success

Day 3 vs. Day 5 Transfer

Another big decision many couples need to make is whether to transfer an embryo on day 3 or day 5 (that is, once the fertilized egg has been growing and dividing for three days post-retrieval or 5 days post-retrieval).

Day 3

A day 3 embryo is known as a cleavage stage embryo and should be around 6-10 cells. The embryo gets graded on the evenness and symmetry of the cells, and the amount of fragmentation. If only a couple of embryos are available, or they are not developing well, some doctors like to perform a day 3 embryo transfer.  This is because these embryos may do better in the natural incubation of the uterus, and this approach avoids the risk of the embryo(s) not making it to the blastocyst stage in the lab.

Day 5

Day 5 is when the embryo should be reaching the blastocyst stage. A blastocyst consists of a fluid-filled cavity, the inner cell mass (a ball of cells that hopefully becomes the baby), and the surrounding trophectoderm cells (which invade the endometrium to undergo implantation). The cavity of the embryo needs to expand fully until it hatches out before implanting.

Not all fertilized eggs make it to the blastocyst stage.  The embryos that stop developing usually do so as they cannot activate their genome (which occurs after day 3), and so these embryos arrest (stop developing) or develop poorly. Therefore, if an embryo makes it to a good quality blastocyst on day 5 we know that is it more likely to keep developing compared to the ones that stopped at day 3.

Studies show that success rates between day 3 and day 5 embryos are comparable and therefore certain circumstances will vary in what is the best option. The best one for you is individual to your circumstances and what your specialist feels is right for you.

Answering your Questions

Question 1

Do 5-day and 6-day blastocyst embryos with the same quality rating have similar live birth rates? I saw different opinions online but so far I am unable to find any concrete randomized test results with large samples.

– Rachel

Answer: Statistically, day 5 embryos do have a higher chance of pregnancy and a paper was published by Fertility and Sterility (Shapiro et al., 2001) that showed nearly a double chance with embryos that made blastocyst on day 5. However, there are still many day 6 embryos that result in pregnancy. A study published by Reproductive Biomedicine Online (Yee & Tian, 2019) showed significantly fewer euploid embryos on day 6 embryos (43% vs 53% on day 5s) but that embryos that are euploid have the same chance of success regardless of the day of development.

IVF abd ICSI questions answered

Question 2

My husband and I were unsuccessful in creating an embryo out of 12 mature eggs/sperm. My doctor said it would be an uphill battle to try again; since the reason is unknown…what can I do to try to improve this or figure out what is the cause? – Laura

Answer: It is up to your doctor to investigate what is going on and for this, he may look at both egg and sperm factors. It doesn’t necessarily mean that you will get the same results in a subsequent cycle; some patients get better results with different stimulation protocols or even just by trying ICSI if IVF alone was previously used before.

Some factors that could have impacted your previous cycle could be DNA fragmentation of sperm or poor egg quality. Maternal age is one of the biggest factors that can impact embryo quality.  Maternal age specifically can impact the progression of embryos past the day 3 point.  Some women of advanced maternal age opt to proceed with donor eggs from a younger donor.  There are also some approaches that can be used to help increase egg quality and sperm health and you can speak with your doctor about taking a few cycles to improve gamete (egg and sperm) quality before your next round.

About the Author

My name is Kristen and I am an Accredited Embryologist in Perth, Australia.

After going through my own struggles to conceive, I became passionate about educating others on the science behind fertility and fertility treatment to make it a more positive, less stressful experience. I Like My Eggs Fertilised is a place for all things IVF and embryology where I can help educate and support you on your fertility journey.

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