Things You Need To Know About Blastocyst

How do they come to be? What stages will they go through? How does the IVF lab tell if it is a good embryo during in vitro fertilization? Should you be transferring 1 or more embryos? Are you more likely or less likely to have more than 1 child?

Babies and Us Fertility Created on 7th Mar, 22

Blastocysts may not be a term that seems particularly pleasant, and it is not just due to its name that sounds like something out of NASA or a warzone. You cannot see an embryo except under a microscope, so they are a bit of a mystery. So when you decide to undergo IVF (in vitro fertilization) and learn about embryos for the first time, it is natural to have many questions. 

How do they come to be? What stages will they go through? How does the IVF lab tell if it is a good embryo during in vitro fertilization? Should you be transferring 1 or more embryos? Are you more likely or less likely to have more than 1 child?


Please visit us at Babies & Us Fertility IVF & ICSI Centre, a world-class fertility centre in Mumbai. Our highly skilled and knowledgeable team will be happy to answer all your questions.


In this article, we have listed a few important things you should know about blastocysts.


What is a blastocyst in the IVF process?

In the IVF (in-vitro fertilization) procedure, your doctor will prescribe fertility drugs to encourage the discharge of healthy eggs from your ovaries. The eggs are then extracted from your ovaries and fertilized with your partner’s sperm in a clinic. 


Once fertilized, the embryo is planted in your uterus. Finally, the embryo must attach itself to your uterine wall for a pregnancy to begin. 

Transferring a fertilized embryo to a female uterus is a crucial step of the procedure. A blastocyst is an embryo that is 5 – 6 days old. 


Till a decade ago, doctors would transfer 3-day old embryos. Most clinics now feel that transferring more developed embryos – embryos that are 5 - 6 days old and have entered the blastocyst stage – increases the likelihood of an ongoing pregnancy.


When is an embryo transfer required?

The IVF procedure and embryo transfer are utilized when natural fertilization is not an option or is prevented by a condition. An embryo transfer can be done for a variety of reasons, including:


  • Fallopian tube damage: Embryos move via the fallopian tubes on their way to the uterus, so if the tubes are blocked or compromised, the fertilized eggs cannot reach the womb.
  • Endometriosis: In this disorder, tissue from the uterus gets implanted outside and starts growing outside the uterus. This can disrupt a woman's reproduction functions.
  • Ovulation disorder: Irregular ovulation means fewer eggs are available for successful fertilization, and your doctor may recommend the IVF procedure.
  • Genetic disorders: Genetic abnormalities, such as sickle cell anemia, cystic fibrosis, etc., can also inhibit pregnancy.
  • Uterine fibroids: These are tiny non-cancerous tumors on the uterus wall that sometimes may cause inefficiency in an egg's ability to plant itself in the uterus.
  • Premature ovarian failure: This is when the ovaries are not able to generate enough estrogen or release eggs properly.
  • Age: The chances of conceiving naturally become harder as we age, so IVF can be a good option.
  • Natural fertilization failure: The causes include poor sperm movement, testes injury, semen anomalies like misshaped sperm affecting its ability to penetrate the egg.


Babies & Us Fertility IVF & ICSI Centre is among the best IVF clinics in Mumbai, providing sophisticated fertility treatments to couples facing issues with natural conception. Single women who want to save their youthful, healthy eggs for motherhood in the future can opt for egg freezing.


We have pioneered several strategies to increase the rate of pregnancy success and live birth.


Is blastocyst (5 – 6 day embryo) transfer better than 3-day embryo transfer?

An embryo that survives for 5 days is more suitable for implantation and successful pregnancy. Many embryos do not survive until the 5th day; for example, an embryo will usually stop developing by day 3 if there is a serious problem with sperm quality.


However, a healthy diet can assist embryos in reaching day 5, and according to numerous researches, blastocyst growth and culturing have several benefits. Blastocyst transfers have a more significant chance of succeeding than early transfers.


Should I be worried that fewer embryos will survive till the blastocyst stage?

Some patients are concerned that there will be fewer or no extra embryos to freeze in the future. This is a baseless argument. It is preferable to get to day 5 and determine the quality of your embryo. Yes, a few embryos will not last till the 5th day and will be lost in the process. However, with any luck, you will be able to transfer the finest one and freeze 1 or 2 good ones for the future.


IVF patients sometimes ignore freezing embryos for a 2nd attempt. Frozen embryo transfers, especially those involving blastocysts, are practically as successful as fresh embryo transplants. So, here is a strategy. On day 5, if you have 2 blastocysts, implanting 1 and freezing the other would be a good idea. 


Is it better to insert 1 blastocyst or 2?

Single embryo transfer has been proven to be the best option. Thanks to advances in extended culture technologies and cryopreservation, the blastocyst stage embryos are of better quality even after freezing.


Gone are days of taking chances with multiple embryo transfers known for raising the risk of multiple pregnancies. 



Years ago, IVF clinics would implant up to 4 embryos that were 3 days old, and everybody involved (medics and the family) would hope for the best. The possibility of having multiple pregnancies was stressful until the dating scan (between 10 - 13 weeks).


Blastocyst implantation is the best option for many couples. Blastocysts help you in improved decision-making and having more control over outcomes. While a study published in 2019 found that blastocyst transfers raised the likelihood of premature birth and bigger babies, the probability was very minor. 


Choosing the right fertility centre is critical before undergoing a blastocyst transfer. We are here to help you in your beautiful journey of parenthood. 


Please schedule an appointment with our highly-experienced team at Babies & Us Fertility IVF & ICSI Centre. Let us work together to create the family you long for and the future you desire.