embryo donation

The path to parenthood can take many roads. There is no single “right way” to become a parent, so you may be debating which path is the right one for you. Two options include egg donation or adoption. If you’re asking yourself “should I adopt or find a donor?” then this article is for you.  Let’s delve into some of the pros and cons to see what feels best for you and your future family. 

Egg donation

The first child born from egg donation was reported in Australia in 1983 and the first American child born from egg donation was in February 1984. Before this medical intervention, for most,  adoption was the only path to parenthood. Egg donation opened the door for more people to become parents. With egg donation, those who are experiencing infertility, have high risks of passing on genetic disorders to their offspring, or have dealt with multiple IVF failures in the past, can have children. 

Pros of using donor eggs

• You can fulfill your dream of raising a child and becoming a parent.
• Donor egg IVF has high success rates, allowing childless people / couples to start a family.
• The opportunity to have a child with a biological relation to the father and biologically related siblings.
• If you are biologically female and plan on carrying the pregnancy, you can still experience delivery and nursing.

Cons of using donor eggs

• It can take a long time to find a donor that you connect with.
• It can be expensive, though with our Family by Co platform, we’ve removed cash compensation for donors from the equation. Instead, our members freeze their eggs entirely for free when giving half of the eggs retrieved to your family.
• Loss of a genetic tie to the mother.
• Fear about telling your child and other people in your life
• There are no guarantees that an embryo will be created.

Adoption

Adoption is the legal process through which a person assumes the parenting responsibilities for someone else's biological child. The concept of adoption exists across cultures and countries and may be traced all the way back to 6th century AD Roman Law. During this time, if the family patriarch did not have a male heir, an heir could be adopted. This was important for the Romans because by adopting one another’s sons, the nobility ensured the wealth would stay within a few families. In the United States, the first modern adoption legislation, the Adoption of Children Act, was passed in Massachusetts in 1851. This act required judges to determine that adoptive parents had “sufficient ability to bring up the child” and that “it is fit and proper that such adoption should take effect.” Today, adoption can take many forms - open, semi-open, domestic and international. 

Pros of adoption

• You can fulfill your dream of raising a child and becoming a parent.
• You get to share your love with a child that may otherwise not have had the best opportunities in life. Studies have shown that adoptive children are less likely to abuse drugs or alcohol and more likely to graduate from high school and go on to college than those who remain in foster care. They are also more likely to have successful careers and strong relationships.
• Because you are helping birth parents who may have not otherwise been able to care for the child, the parents can feel at peace knowing their child will be loved and taken care of.

Cons of adoption

• It can take a long time - anywhere from 9 to 12 months - to find an adoption opportunity.
• It can be very expensive. For domestic infant adoption the cost can be anywhere from $40k to $70k and up.
• The birth parent has a right to change their mind. Depending on the state, that may be anytime while pregnant or up to 30 days after the adoption. 
• Since most adoptions are open, there is a chance that the birth parent may want to be a part of the child’s life, and that may be difficult for some adopting parents.
• Different states have different laws on who can become an adoptive parent based on age, sexual orientation and even religious affiliation.

Embryo donation

Embryo donation is typically not the first choice for most couples starting  infertility treatment, but if you have not been successful with traditional infertility treatment using your own eggs and/or sperm, or are having problems finding a donor, this is a great viable option. 

Pros of embryo donation

1. You can fulfill your dream of raising a child and becoming a parent.
2. Because the embryos are already created and readily available, you can get started whenever you are ready.
3. Can be less expensive than egg and sperm donation and adoption.
4. You can still experience pregnancy, delivery, and nursing.
5. There won’t be a genetic imbalance if only one partner uses a donor.

Cons of embryo donation

1. Embryo donation is technically an adoption. Because you may not have all the medical history of one or both the donors, it can potentially introduce some unpredictability into the genetic makeup of the family.
2. Although readily available, because it is an adoption, it can still sometimes take a long time to match with an embryo.
3. There are no guarantees that an embryo transfer will be successful and result in a pregnancy and delivery.

Which one is right for me?

The decision to use medical intervention to conceive a child or to go through an adoption agency to start a family is an extremely personal one. As you can see above, all paths come with their own set of unique challenges. The best thing you can do is become educated in all your options. Get second and third expert opinions. Seek out legal counsel and ask questions. No one but you can make this decision, but whatever decision you choose, know that you are not alone. Many have walked down these roads to have their family and none of them would have done it any other way.

Embryo grading plays a critical role in assisted reproductive technology (ART), providing valuable insights into the quality of embryos and their potential of developing into a healthy pregnancy. But — and I speak from personal experience — embryo grading can also be one of the most complicated aspects of ART (an already complex process!) to navigate. In my case, I actually had one fertility clinic — where I did my retrieval cycles — disagree with my new clinic about which embryo was the best quality to transfer. When transfer day came and the embryologist read aloud which embryo they’d be using, imagine my surprise when it was a different embryo than the one I expected. 

Thankfully, my (very patient) reproductive endocrinologist walked me through my clinic’s data on various embryo grades and the success rates of each. And luckily, this embryo transfer resulted in the healthy birth of my son. But, since we all don’t know what we don’t know, the goal of this article is to ensure that you are armed with all the facts about embryo grading. We’ll discuss how different embryo grades influence the chances of success in ART procedures, including IVF. That way, you can ask the right questions, make more informed decisions, and maximize your prospects of achieving a successful pregnancy — with donor eggs or your own. Let’s jump in. 

What is embryo grading?

Embryo grading involves the visual assessment of morphological characteristics of an embryo by a trained embryologist, to evaluate the quality of embryos and their chances of developmental success into a healthy pregnancy. In other words, embryo grading is important because it can give you an idea of your odds of success prior to transferring that embryo. It can also provide insight into whether or not another IVF cycle might be beneficial, with or without adjustments to the treatment protocol.  

During the embryo grading process, embryologists evaluate factors such as cell number, cell symmetry, fragmentation, and the appearance of the zona pellucida. These assessments are typically conducted at the embryo’s cleavage stage (day 2 or 3 of development) and the blastocyst stage (day 5 or 6 of development) following fertilization, for embryos that have made it to this point. 

Understanding different embryo grades and their significance

Embryo grading systems provide a framework for embryologists to assign ratings based on specific morphological features. And while these systems are standardized, the grading system used can vary depending on the clinic. Embryo grading systems are equally applicable in donor egg IVF cycles, enabling the evaluation of embryos derived from donor eggs. 

Some commonly used embryo grading systems include: 

Gardner's blastocyst grading system 

The Gardner embryo grading system (sometimes referred to as the Gardner and Schoolcraft system) is widely used, and takes into account three main factors: expansion grade, inner cell mass (ICM) grade, and trophectoderm (TE) grade. Here's a breakdown of each component:

Expansion grade 

The expansion grade refers to how much the embryo has grown and expanded in the culture medium. It is usually assessed on a scale from 1 to 6. Here's what each grade means:

• Grade 1: The embryo is not expanded or only slightly expanded.
• Grade 2: The embryo has started to expand, with a small fluid-filled cavity called a blastocoel.
• Grade 3: The embryo has further expanded, and the blastocoel is larger.
• Grade 4: The embryo is even more expanded, with a significant blastocoel.
• Grade 5: The embryo has expanded further, with the blastocoel filling most of the embryo.
• Grade 6: The embryo has fully expanded, with a large blastocoel and thinning of the outer layer.

A higher expansion grade generally indicates better developmental potential.

Inner Cell Mass (ICM) grade

The ICM is a cluster of cells inside the embryo that will eventually develop into the fetus. It is graded based on its appearance and overall quality. Here's a simplified breakdown of ICM grades:

• Grade A: The ICM is tightly packed, with many cells and high density.
• Grade B: The ICM is looser or slightly less dense than Grade A, but still considered good quality.
• Grade C: The ICM is fragmented or has fewer cells, indicating lower quality.

Embryos with a higher ICM grade have a higher likelihood of successful implantation and pregnancy.

Trophectoderm (TE) grade

The trophectoderm is the outer layer of cells that will develop into the placenta. It is also graded based on its appearance and overall quality. Here's a simplified breakdown of TE grades:

• Grade A: The TE is tightly packed, forming a cohesive layer.
• Grade B: The TE is slightly looser or has minor irregularities but is still considered good quality.
• Grade C: The TE is fragmented or has more significant irregularities, indicating lower quality.

Embryos with a higher TE grade generally have a higher chance of successful implantation and pregnancy.

Combining the expansion grade, ICM grade, and TE grade provides an overall assessment of the embryo's quality and potential for successful implantation and pregnancy. However, the grade of the embryo is just one piece of the puzzle. The success of embryo transfer depends on various individual factors, including your age, overall fertility health, uterine environment, and the skill of the doctor.

Society for Assisted Reproductive Technology (SART) grading system

The SART embryo grading system focuses on the evaluation of cleavage-stage embryos (day 2 or 3). It takes into account parameters such as the number and symmetry of blastomeres, the presence of fragmentation, and the appearance of the cytoplasm. Embryos are generally graded on a scale from 1 to 4:

• Grade 1: These embryos are considered of excellent quality. They have equal-sized and symmetrical blastomeres (cells) without any fragmentation. These embryos have a higher likelihood of successful implantation and pregnancy compared to lower-graded embryos.
• Grade 2: These embryos are still of good quality but may show minor asymmetry or minimal fragmentation. Although they may have slight imperfections, they still have a reasonable chance of successful implantation and pregnancy.
• Grade 3: These embryos have moderate asymmetry or fragmentation. The presence of moderate irregularities may slightly decrease their chances of successful implantation and pregnancy compared to higher-graded embryos.
• Grade 4: These embryos exhibit significant asymmetry or fragmentation. These embryos have more substantial irregularities, significantly reducing their chances of successful implantation and pregnancy compared to higher-graded embryos.

Cummins' embryo grading system:

The Cummins' grading system is another method used to assess cleavage-stage embryos. It is quite similar to the SART system, but while the SART system primarily focuses on the symmetry of blastomeres and the degree of fragmentation, the Cummins system emphasizes the size and fragmentation of those blastomeres. 

Unlike the SART grading system, through the Cummins embryo grading system, embryos are actually scored on a scale from 1 to 5 (vs. 4):

• Grade 1: Embryos that receive a Grade 1 are considered of excellent quality. They have blastomeres (cells) that are of equal size and show no fragmentation. Grade 1 embryos have a higher chance of successful implantation and pregnancy compared to lower-graded embryos.
• Grade 2: Grade 2 embryos are still considered good quality, but they may have minor imperfections. These embryos might have some minor asymmetry or minimal fragmentation, meaning that the blastomeres may not be perfectly equal in size, and there may be some small fragments. Grade 2 embryos still have a reasonable chance of successful implantation and pregnancy.
• Grade 3: Embryos with Grade 3 have moderate asymmetry or fragmentation. This means that the blastomeres may show more unevenness in size, and there may be a moderate amount of fragmentation present. Grade 3 embryos have a slightly lower chance of successful implantation and pregnancy compared to higher-graded embryos.
• Grade 4: Grade 4 embryos have significant asymmetry or fragmentation. The blastomeres may show significant variation in size, and there may be a substantial amount of fragmentation present. Grade 4 embryos have a lower chance of successful implantation and pregnancy compared to higher-graded embryos.

How important are embryo grades, anyway? 

Embryo grades provide valuable insights into the developmental potential of embryos, but they are not the sole determining factor of success. It’s important to recognize that grading systems primarily evaluate morphological characteristics and do not consider other crucial aspects, such as genetic abnormalities or the embryonic environment. 

While higher-graded embryos generally have higher implantation rates, it is not uncommon for lower-graded embryos to still result in successful pregnancies. The decision regarding embryo selection should involve a comprehensive evaluation of individual patient factors, including age, fertility history, and the number of available embryos.

How to know a "good" embryo grade

Understanding how to interpret embryo grades is vital for patients undergoing IVF. Typically, embryos with higher grades possess certain characteristics indicative of better developmental potential. For instance, in the Gardner system, high-quality blastocysts often have a fully expanded blastocoel, a tightly packed ICM with many cells, a well-formed TE with few or no fragments, and a smooth and even zona pellucida. These features suggest a greater likelihood of successful implantation and subsequent pregnancy. 

While these grading systems provide a standardized approach, there may still be some variability in interpretation between embryologists and clinics, based on that clinic’s own success rate data with embryos of different grades. Additionally, newer systems and modifications continue to emerge, aiming to improve the accuracy and reliability of embryo grading.

Understanding the grading system used by your fertility clinic and discussing it with your reproductive specialist can help you interpret and interpret the grading of your embryos more effectively. Remember, the grading system used may influence the way embryos are selected for transfer or cryopreservation.

Which embryo should I transfer first?

If you’ve made it to the point where you have more than one blastocyst embryo available to transfer, congratulations! That’s a huge weight off of your shoulders. Now, you’re likely focused on the next big decision: which embryo should I transfer first? Doctors may have different opinions on this, depending on various factors. Here are a few considerations as you and your doctor weigh this decision: 

Implantation potential

As we previously mentioned, higher graded embryos generally have a higher potential for successful implantation and pregnancy. They often exhibit better morphological characteristics and developmental quality, which can increase the chances of successful embryo implantation and subsequent pregnancy. Therefore, some clinicians may recommend transferring higher graded embryos first to maximize the likelihood of achieving a successful pregnancy.

Number of embryos

If you have a limited number of embryos available for transfer, some doctors may advise starting with the higher graded embryos. This approach aims to optimize the chances of achieving a pregnancy early in the treatment process, preserving any remaining higher graded embryos for future transfer attempts. 

Depending on how many kids you want, other doctors may advise the opposite — if you know you want two children, but you transfer a higher graded embryo earlier and get pregnant right away, that will delay your availability to potentially do another IVF cycle again should your lower-graded embryos not result in another pregnancy. Also, if you transfer a lower graded embryo and it does stick, that will only further increase your chances of a successful pregnancy down the line with another embryo, especially a higher graded one!

Patient-specific factors

Factors such as your age, fertility history, previous IVF outcomes, underlying medical conditions, and specific treatment goals should be taken into consideration. If you’ve undergone previous IVF cycles and had unsuccessful outcomes with higher graded embryos, your doctor might consider altering the approach and prioritize transferring lower graded embryos first to try something different. Although higher graded embryos generally indicate better chances of a successful pregnancy, it’s not impossible to have a baby using a lower graded embryo. They still show implantation potential and result in successful pregnancies in some cases.

We recommend talking with your REI to receive personalized guidance based on your specific situation. They can provide the most up-to-date clinical information, evaluate your individual factors, and offer recommendations tailored to your needs and timeline. 

Embryo grading for donor egg IVF cycles

With a donor egg IVF cycle, embryo grading is equally important. However, other factors, such as the intended parent or gestational carrier’s uterine environment and receptivity, still play a significant role in the success of donor egg IVF cycles. It’s also critical to understand that embryo grading is not indicative of the presence or absence of chromosomal abnormalities or specific genetic factors.

At Cofertility, the average number of mature eggs a family receives and fertilizes is 12. Some intended parents want to do two egg retrievals with the donor which is definitely possible. We also ask each of our donors whether they are open to a second cycle as part of the initial application — many report that they are!

You can see how many eggs are retrieved in the first cycle and go from there. If, for any reason, the eggs retrieved in that round do not lead to a live birth, our baby guarantee will kick in and we’ll re-match you at no additional match deposit or Cofertility coordination fee.

In conclusion

Embryo grading serves as a valuable tool in assessing the developmental potential and quality of embryos in assisted reproductive technology (ART). While higher-graded embryos generally exhibit higher implantation rates and better chances of success, embryo grade is not the end-all-be-all when it comes to predicting pregnancy outcomes. 

Grading systems primarily evaluate morphological characteristics and do not account for genetic abnormalities or the embryonic environment. Because of this, the decision regarding embryo selection should involve a comprehensive evaluation that considers multiple factors beyond just the assigned grade. Your fertility doctor can provide personalized guidance to optimize your chances of achieving a successful pregnancy based on their specific circumstances. We wish you all the best!

The embryo transfer is an exciting and pivotal time in the in vitro fertilization (IVF) process. It’s when the embryo is transferred to the uterus of the intended mother or a gestational carrier, in hopes that it snuggles in for nine months and becomes the child you’ve always dreamt of.

You may be wondering if you should transfer one (single embryo transfer, or SET) or two (double embryo transfer, or DET) embryos, to increase your chances of a happy, healthy baby.  

This article will dissect the complexities of this decision-making process, taking into consideration both personal choices, and also help answer this question to intended parents using donor eggs.

First off, what is an embryo transfer?

Understanding what an embryo transfer entails is important to appreciating the decision-making process between single or double embryo transfer.

After an egg, or eggs, are fertilized with sperm, an embryo develops in a controlled laboratory environment for a few days under the careful watch of a trained embryologist. If and when the embryo reaches a particular developmental stage (ie. blastocyst stage), it is suitable for transfer.

Now, at this point, some families opt to do PGT testing, which looks to see if the embryo contains the correct amount of chromosomes. Embryos with the right number of chromosomes — 46 — are considered “euploid,” and those with extra chromosomes or chromosome deletions are considered “aneuploid.” PGT is a way to screen for genetic disorders in embryos created through IVF before they are transferred to the uterus. Read more about PGT testing.

All embryos are then “graded” by the embryologist to evaluate their quality and chances of developmental success into a healthy pregnancy. Based on this assessment, your fertility doctor will recommend the order and number of embryos to be transferred. This is the stage where the choice between a single embryo transfer or a double embryo transfer is usually made.

Finally, the selected embryo(s) is transferred to the uterus via a thin catheter, typically under ultrasound guidance. If the embryo implants in the uterine lining, it may lead to pregnancy.

Embryo transfers and the history of IVF

When IVF was in its infancy, following the birth of the first IVF baby, Louise Brown, in 1978, the process was distinctly different from what it is today. In the early days, IVF involved the transfer of fresh embryos, without the technological advancements available now. This is because we didn’t have the technology to freeze and preserve embryos for genetic testing or future transfer.

At the time, this approach was taken to increase the likelihood of pregnancy, compensating for the uncertainties around embryo viability. However, this practice led to a higher incidence of multiple pregnancies (pregnancies of twins, triplets, or more), with associated health risks for both mothers and children.

With the development of cryopreservation techniques, it became possible to freeze embryos for later use, allowing for more flexibility and planning in the transfer process. This technology also enabled better timing for embryo transfer, and gave patients a break between the egg retrieval and embryo transfer. 

Simultaneously, genetic testing of embryos significantly increased the success rates of IVF, even with the transfer of a single embryo.

Guided by these advancements, the American Society for Reproductive Medicine (ASRM) now recommends elective single embryo transfer (eSET) in most cases, especially for women under the age of 35 with a favorable prognosis. This shift towards eSET reflects a growing emphasis on minimizing the risks associated with multiple pregnancies without compromising success rates.

So how many embryos should I transfer?

The decision regarding the number of embryos to transfer should weight the potential success rate against the risks associated with multiple pregnancies. Factors such as age, the quality of the embryos, previous IVF attempts, and individual patient preferences play an important role in this decision.

Let’s go through the pros and cons of each option:

Elective single embryo transfer (eSET)

Pros:

• Reduced risk of multiple births: eSET almost eliminates the chance of a multiple pregnancy (twins, triplets, etc.), thus reducing the associated health risks for both the mother and the babies.

Cons:

• Possibly lower success rates: Some studies have shown that eSET may yield a slightly lower live birth rate compared to double embryo transfer.

Double embryo transfer (DET)

Pros:

• Potentially higher success rates: By transferring two embryos, DET may improve the chances of pregnancy, especially when there are concerns about embryo quality.
• Chance to have twins: If you always wanted twins, transferring two embryos gives you a better chance of that dream.

Cons:

• Riskier pregnancy and birth: DET significantly increases the risk of twins or higher-order multiples, leading to more complicated pregnancies and a higher chance of preterm births and low birth weight.

It’s important to discuss this with your fertility doctor and get their input. Because ASRM usually recommends a single embryo be transferred, in most cases fertility doctors will recommend just that.  

How many donor egg embryos should I transfer?

When donor eggs are utilized, a couple other factors need to be considered. Donor eggs are from younger women who have gone through extensive medical screening, and thus, embryo quality tends to be higher. Because of this, it increases the chances of success, even if the mother is older, or if she experienced failed IVF in the past. In donor egg cases, eSET is generally preferred to minimize the risk of multiple pregnancies while maintaining a satisfactory success rate.

Summing it up

If you are wondering if eSET or DET is right for you, talk to your fertility doctor. They can help talk you through the pros and cons, and help select an approach that best fits your needs.

For those using donor eggs, the generally higher quality might lean the decision towards eSET, while personal preferences and specific medical situations might suggest otherwise. By carefully considering the nuanced pros and cons, you can make a well-informed choice in your pursuit of parenthood. We wish you all the best!

Starting with a fertilized egg, embryo development is a complex biological phenomenon that has fascinated scientists for centuries. With advances in assisted reproductive technology (ART), particularly in vitro fertilization (IVF), our understanding of embryo development has expanded dramatically — contributing to the birth of 91,771 ART-conceived babies in 2022! 

This article walks through the step-by-step processes involved in unassisted and assisted embryo development, highlighting underlying biological events, how IVF works, and the factors influencing fertilization success. Let’s jump in.

It starts with the egg 

Ovulation is the starting point of embryo development. It is the part of the menstrual cycle when one ovary releases a mature egg. Once it is released, the egg moves down into one of the fallopian tubes, where it can survive for about 24 hours. This can result in pregnancy if the egg gets fertilized by sperm during that time – if it doesn’t get fertilized, the egg will break down and eventually will shed along with the lining of the uterus when you have your period.  This typically occurs around the 14th day in a 28-day cycle, though not for everyone. The day of ovulation varies based on cycle length, anything ranging 21 - 35 days is considered normal. Hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH) play critical roles in inducing ovulation. These hormones are always in your body, but your FSH levels fluctuate throughout the menstrual cycle, typically peaking just before LH levels peak to trigger ovulation.

During an egg freezing / IVF cycle, understanding the timing of your menstrual cycle is important as it influences the scheduling of your treatment. Ovulation is carefully controlled through the administration of hormonal drugs that stimulate the ovaries to produce multiple eggs and bring them to peak maturity. The development of these eggs is monitored through regular ultrasounds and blood tests, which are crucial to ensure the specific medication protocol you are given is personalized to you. Once the eggs are mature, they are retrieved surgically under anesthesia.

Then, the eggs are fertilized 

Fertilization marks a pivotal stage of embryo development. During unassisted embryo fertilization, it occurs in the fallopian tubes and begins when a sperm cell breaks through the outer layer of the egg, the zona pellucida. This penetration triggers reactions that prevent other sperm from entering the egg. Then, the nuclei of the sperm merge with the nuclei of the egg, combining their genetic material to form a zygote, the earliest stage of the embryo.

During IVF, fertilization takes place in a lab setting, using the retrieved eggs and sperm. An embryologist combines each egg with sperm, under a controlled, microscopic watch to monitor daily development. Ideally, the same response occurs as during an unassisted fertilization process. To enhance success rates, especially in cases of male factor infertility and low sperm counts, a single sperm is injected directly into the egg using a technique called intracytoplasmic sperm injection (ICSI). 

The early embryo develops through cleavage 

Once the fertilized egg has created a zygote, it then begins a series of rapid divisions in a process known as cleavage. This stage of embryo development involves the embryo splitting without growing in size, essentially forming a compact ball of cells. Cleavage is vital as it transforms the single-cell zygote into a multicellular entity, setting the foundation for further differentiation and growth. Both in unassisted conception and IVF, studies have shown the quality and speed of these divisions can be an early indicator of the embryo's health and viability.

The blastocyst forms 

About five days after fertilization, the developing embryo hopefully(!) reaches the blastocyst stage. This is when the embryo is made up of two parts: a cluster of cells inside that will develop into the baby (called the inner cell mass) and a shell on the outside that will help form the placenta (called the trophoblast). 

During unassisted conception, the blastocyst travels from the fallopian tube to the uterus throughout this five day period. During IVF, however, the blastocyst first develops within the lab and then is frozen. At this point, many families opt for genetic testing of the embryo. 

Preimplantation genetic testing for aneuploidy (PGT-A) allows families to know whether embryos possess the right number of chromosomes. A “euploid” embryo is genetically healthy enough to transfer. Embryos with chromosomal additions or deletions are considered aneuploid. Mosaics are somewhere in between and we’re still learning more about their potential. 

PGT-M (preimplantation genetic testing for monogenic disorders), on the other hand, takes place if there is a specific genetic diagnosis for which both reproductive partners are carriers. This technology allows embryologists to identify embryos possessing those specific genetic abnormalities. That way, parents can choose to avoid transferring one of these embryos if it would put the future child at risk. 

A healthy embryo is transferred and grows in the uterus

Your PGT results (should you choose to pursue that testing), combined with the grades given to each of your blastocyst embryos, will both factor into your and your doctor’s decision on which embryo would be best suited for transfer. 

During IVF, an embryo transfer procedure is done with great care under ultrasound guidance to optimize the placement of the embryo(s) within the uterine cavity, enhancing the chances of successful implantation. The timing of this transfer is crucial and is carefully synchronized with the recipient's menstrual cycle to ensure the uterine lining is optimally receptive. 

Implantation and fetal development

Ideally, the hope is that the transferred blastocyst will attach itself to the uterine wall— a process known as implantation. During implantation, the outer layer of the blastocyst, known as the trophoblast, connects itself to the uterine lining. As we mentioned, timing is everything — implantation success is influenced by the hormonal balance of the body and the receptivity of the uterine lining, which needs to be thick enough to “accept” the embryo. This will eventually grow into placenta, and will be an essential connection for the transfer of nutrients and oxygen to the embryo as it develops into a fetus and, ultimately, a baby. 

The heart is the first organ to develop within an embryo — by the sixth week of pregnancy, the embryo may have developed an actual heartbeat, which can be measured on ultrasound.

Factors influencing embryo development success

Several factors affect the success of both unassisted and assisted embryo development:

1. Age and quality of eggs: Older women tend to have fewer eggs, and the quality of eggs decreases with age, affecting fertilization rates and embryo development. Utilizing donor eggs can significantly improve outcomes in IVF treatments.
2. Sperm quality: Parameters such as sperm count, motility, and morphology are crucial in both unassisted and assisted fertilization processes.
3. Clinic and lab quality: Not all fertility clinics are created equal, and the same goes for labs. If you have not yet begun the IVF process, ask your clinic about their blastocyst development success rates (it’s key to use this language, as opposed to fertilization rate, for example) and feel free to call other local clinics and do the same. 
4. Embryonic development: The ability of an embryo to reach the blastocyst stage is a key indicator of its viability and potential for successful pregnancy.

A recent study examined a few reasons why embryo growth may stall — in summary, this is largely due to chromosomal fragility and abnormalities. If possible, we recommend undergoing genetic carrier screening before pursuing IVF so as to make the experience as successful as possible and ideally provide a healthy pregnancy. 

Summing it up

In conclusion, the path from egg to blastocyst formation is pretty incredible and requires the completion of several successful steps even before a transfer attempt. As technological capabilities expand within the field of embryology, so too does the potential to assist those facing challenges in unassisted conception. 

If you’re interested in working with an egg donor to help create embryos and start or grow your family, click here to browse our platform with tons of egg donors eager to help. 

FAQs about embryo development

What percentage of fertilized embryos make it to day 5?

About one-half of fertilized embryos continue developing to become a day 5 blastocyst. When an embryo is created using donor eggs, this stat jumps to 60%. 

How long does it take for an embryo to develop after IVF?

In IVF, embryos are typically cultured in the laboratory for 5-6 days to reach the blastocyst stage, which is considered optimal for transfer. However, occasionally embryos may be transferred earlier, at the cleavage stage (day 3). 

Where does the embryo develop?

In unassisted conception, the embryo develops in the uterus. After fertilization, the embryo travels down the fallopian tube and reaches the uterus, where it undergoes several stages of development starting from a zygote to a blastocyst. Successful implantation into the uterine wall is essential for the continued growth and development of the embryo.

While the implantation process remains the same for an embryo’s development during IVF, the actual fertilization process for assisted conception takes place within a lab, where an embryologist combines an egg with sperm under close watch. Only once the embryo has spent 5 days developing into a blastocyst is it transferred into the recipient’s uterus, or may be frozen for a future embryo transfer cycle. 

What is the first organ to develop in the embryo?

The first organ to develop in the embryo is the heart. The heart begins as a simple tube-like structure and starts beating and pumping blood by around the 22nd day after conception, which is essential for the circulation of nutrients and oxygen to the developing embryo.

When does an embryo develop a heartbeat?

An embryo typically develops a heartbeat by the end of the fifth week of pregnancy, which is about three weeks after fertilization. This milestone can often be seen during an early ultrasound scan, and is a crucial indicator of the embryo's viability.

What is preimplantation genetic testing (PGT)?

PGT is a process that screens embryos created through IVF for specific genetic conditions or chromosomal abnormalities. This can help increase the chances of a healthy pregnancy and reduce the risk of miscarriage. Read more about PGT testing here.

Does using frozen eggs affect embryo development?

Research suggests that eggs frozen through vitrification have similar success rates to fresh eggs in IVF. However, the success rates of utilizing frozen eggs still depends on the age of the egg when it was frozen. The younger the egg(s), the greater its potential for successful fertilization and development into a healthy embryo.