Blastocyst Culture and Transfer 

What is Blastocyst culture and transfer?

      A blastocyst is an embryo that has developed for five to six days after fertilization. At this point the embryo has two different cell types and a central cavity. It has just started to differentiate. The surface cells, called the trophectoderm, will become the placenta, and the inner cells, called the inner cell mass, will become the fetus. A healthy blastocyst should begin hatching from its outer shell, called the zona pellucida by the end of the sixth day. Within about 24 hours after hatching, it should begin to implant into the lining of the mother's uterus.

      The ultimate goal of Blastocyst culture and transfer is to provide high quality embryos which are capable of continued normal development, ready to implant and result in live births.

Blastocyst culture and transfer is the most advance in the ART technique. Traditionally, IVF technique, embryos have been transferred to the uterus on the second or third day of development after in vitro fertilization and initial embryonic cell division. This day of embryo transfer has been a compromise between maximizing the degree of embryo selection available through longer culture in the IVF Lab versus minimizing the exposure of the embryos to culture media which, in the past, could only sustain growth for 2-3 days. There are some advantages to culturing the embryos to the blastocyst stage of development prior to transfer. The growing embryo must get over several hurdles before reaching the blastocyst stage. After five days of growth, the cells of the embryo should have divided many times over, and have begun to differentiate by function. The embryos that survive to this stage of development are usually strong, healthy. They are now called Blastocyst. Two important factors had limited the number of embryos that will survive to this stage. First, the inherent "health" of any embryo will dictate its ability to continue to grow and divide. Several eggs may have initially fertilized, but only a few will progress to the four-cell stage, fewer still to the eight-cell stage, and even fewer will develop into Blastocyst. These arrested and / or fragmented embryos do not have the developmental potential to become babies, so it is better to identify these embryos prior to transfer. By allowing the all embryos to grow in the laboratory for five days, they will sort themselves out. The ability to grow embryos for five days to the blastocyst stage of development in the laboratory, rather than the previous traditional three days, allows clinicians to determine with greater certainty which embryos are really the "best" in terms of their potential for implantation. By transferring only Blastocyst with high developmental potential, fewer embryos may be transferred to achieve the high chance of pregnancy. This means fewer multiple gestations (twins, triplets, etc.). Another advantage is that the blastocyst stage of development is the appropriate time to transfer embryos back into the uterus since the developing embryos usually spend their first 4-5 days of life in the Fallopian tubes, not the uterus. Thus the environment for the embryos is appropriate. But blastocyst culture and transfer technique also has a down side; it may be that none of the embryos develop to the blastocyst stage. In that case there will be no embryo transfer. Although that would be a very sad story, but anyway it is better than the high anxiety waits for the first pregnancy test. 

Is Blastocyst culture and transfer for everyone?

The indications for a blastocyst transfer are:

(1) Young or old patient who has approximate 10 eggs per stimulation will have good prognosis.

(2) Patients with one or more failed many treatment cycles, since this would answer the question of whether or not those persons’ embryos are capable of growing to the blastocyst stage.

(3) Unexplained infertility.

(4) Patients who do not want to run the risk of multiple gestations.

(5) Patients who have fewer oocytes retrieved, fewer fertilized or fewer dividing embryos by day three in culture have little advantage using blastocyst culture, since little is to be gained in further embryo "self selection". 

Program Summary for Patients Undergoing Blastocyst Culture and Embryo Transfer

The following is an outline of the basic flow of steps for most patients. 

Blastocyst culture and related procedures require the following steps: 

1. Patient Selection:

A complete evaluation of fertility factors (These are egg, sperm and uterine cavity) is important prior to considering Blastocyst culture and transfer technique. The following conditions can be successfully treated with Blastocyst culture and transfer technique. 

Tubal Disease Patients with tubal blockage or severe pelvic adhesions, or who have not conceived after tubal surgery are good candidates for Blastocyst culture technique. 

Moderate to Severe Male Factor The ability to treat sperm in the lab by various techniques, along with the ability to concentrate large numbers of motile sperm around eggs makes Blastocyst culture and transfer technique a potential treatment for couples whose infertility is due to poor semen quality. 

Endometriosis As endometriosis often results in pelvic anatomy distortion and adhesion, the Blastocyst culture and transfer technique procedure allows the egg and sperm to meet and fertilize in an environment free of endometriomas and be transferred directly into the uterus. 

Immunologic Infertility Blastocyst culture and transfer technique allows fertilization outside the body, away from the destructive actions of anti-sperm antibodies. 

Unexplained infertility that has not responded to other types of therapy Blastocyst culture and transfer has successfully treated such couples. Blastocyst culture and transfer can demonstrate the ability of the sperm to fertilize eggs become to growing embryos and grow to the final stage "the Blastocyst". Rarely, unexplained infertility may be due to defects in gamete function. 

2. Pre-Cycle Evaluation:

To achieve good success rate, it need to meticulous evaluation of three factors (egg, sperm and uterine cavity) that contribute to a favorable outcome with blastocyst culture and transfer. 

A. The first of these is the woman's ability to respond to fertility drugs. While age affects this parameter, measurements of FSH and Estradiol on the third day of the menstrual cycle help us estimate a woman's ability to produce extra eggs in response to fertility drugs. In general, women with high FSH levels and/or early high estradiol are more resistant to ovarian stimulation. 

B. The second factor to evaluate is the uterine environment. It is recommended that the woman undergoes a one-time office hysteroscopy prior to beginning a Blastocyst culture and transfer procedure. The hysteroscopy allow us to look inside the uterine cavity and make sure there are no fibroids, polyps, or scar tissue that could interfere with implantation. If the woman has had a recent hysterosalpingogram (HSG), and the uterine cavity appears normal, the hysteroscopy can be waived. Also, women undergoing Blastocyst culture and transfer should have the length of their uterus carefully measured, in order to accomplish an atraumatic embryo transfer later on.

Cervical cultures for ureaplasma, chlamydia, and gonorrhea are taken before commencing treatment. Organisms such as ureaplasma have been associated with poor reproductive outcome and poor embryonic growth in the laboratory.

Finally, the uterine lining is evaluated prior to ovulation using a sonogram. Certain patterns of uterine lining development especially when the lining is thin are associated with poor pregnancy rates. These sub-optimal patterns can sometimes be improved with estradiol supplementation. 

C. The third factor is the male factor. This requires a semen analysis. In addition, sperm antibodies are measured in both partners. High levels of sperm antibodies can interfere with fertilization in the laboratory, and special techniques are employed to correct this problem. 

Couples undergoing Blastocyst culture and transfer are screened for syphilis, hepatitis and HIV. Patients who have major medical, surgical, or psychological problems are required to be treated before the starting cycle. 

In addition to the above medical evaluation, couples contemplating Blastocyst culture and transfer are informed of the availability of a counsellor. The licensed counsellors are familiar with the emotional impact of infertility and infertility treatments, and can help the couple deal with this important aspect of their care. 

3. Ovulation Induction and Monitoring:

Blastocyst culture and transfer success rates depend upon the numbers of eggs, fertilized eggs, growing embryos or blastocysts available for transfer. Additionally, the egg retrieval must be carefully timed so as to retrieve mature eggs. To accomplish these two goals, ovulation induction medications and careful monitoring are employed. 

Once menses occurs, a sonogram is done to make sure there are no ovarian cysts, and a blood estradiol level is measured to make sure that everything is in control. On a specified day the woman begins injections of Gonadotropins according to a schedule that is provided by the clinic. We arbitrarily call the first day of Gonadotropin administration Cycle Day 1. In order to monitor a patient's response to these drugs, daily sonograms and serum estradiol levels are performed starting on Cycle Day 7. These help us determine when the eggs are ready for collection. 

Once the follicles (containing the eggs) are deemed ready, the patient stops taking Gonadotropins. About 36 hours prior to the anticipated egg retrieval, the patient takes an injection of human chorionic gonadotropin (hCG). This hormone replaces the woman's normal LH surge, and is necessary for a final maturation of the eggs so that they can be fertilized. 

4. Egg Retrieval:

In almost all cases, egg retrieval is accomplished non-surgically using a vaginal ultrasound probe to guide a needle into the ovaries. The procedure does not require general anesthesia and is performed with just simple intravenous sedation. An anesthesiologist administers the sedation to maximize your comfort and safety. As a result, the experience is not painful and recovery is rapid. 
 
 

5. Sperm Processing:

Freshly ejaculated sperm must undergo biochemical and structural change called capacitation before they can fertilize an egg. In a Blastocyst culture and transfer cycle, sperm are capacitated in the laboratory and the motile and healthy sperm are isolated prior to inseminating the eggs. 

6. In Vitro Fertilization:

In-vitro fertilization literally means "fertilization in glass". Follicular fluid removed from the ovaries is examined in our lab for the presence of eggs. These are isolated and placed in culture media where they are allowed to further mature. A few hours later, portions of the processed sperm are placed around each egg. Only 50 to 100 thousand sperms are needed for each egg. This is why men with low sperm counts can often fertilize eggs in the lab. 

The eggs and sperms are left to incubate together in a carefully controlled environment. Approximately 18 to 24 hours following insemination, the eggs are inspected under the microscope to determine how many have been successfully fertilized. These embryos will be kept in the laboratory as they continue to grow and develop until the moment of transfer. 

7. Embryo Transfer:

The embryos are transferred via a thin plastic tube through the cervix into the uterine cavity. They are then deposited in the upper part of the uterus and the catheter is withdrawn. This is generally a painless procedure and the patient remains on bed for 2 hours, after which she is sent home. As implantation will occur in the following two or three days the patient is instructed to rest at home during this time after the transfer. Light activities allowed without stress and most sleep well at night. 

Depending on the quality of the embryos and the couple’s preference, the embryos will be transferred into the woman’s uterus 5 days after egg retrieval. Three days after egg retrieval, the embryos have cleaved and contain 8 cells each. If embryo transfer is performed at this time, approximately 3 to 5 embryos are transferred depending on the couple’s desires and the quality (grading) of the embryos. Currently, we suggest couples to transfer their embryos 5 days after egg retrieval at a more advanced stage of development (blastocyst stage). These blastocysts have a higher implantation rate than embryos grown only three days, and are more likely to succeed in initiating a pregnancy. As result, only two blastocysts need to be transferred to have the same pregnancy rate usually seen when 3 or more embryos that have been grown for only 3 days are transferred into the uterus. As a result, fewer embryos are needed to achieve the same or higher pregnancy rate, with a lower incidence of multiple gestation. 

8. Post-Transfer Management:

During the follow-up phase, the woman receives daily vaginal suppository of progesterone with the goal of enhancing implantation. Ten to twelve days after the embryo transfer, blood pregnancy tests are performed. Rising blood levels of the pregnancy hormone, hCG, indicate that implantation has occurred. Approximately 10 days after the first hCG level, the blood test will be confirmed that the pregnancy is ongoing. Confirmation of a clinical pregnancy is made by ultrasound about 2 weeks later. 

9. Cryopreservation:

Freezing extra embryos gives couples an additional opportunity to conceive without going through stimulation cycle and egg retrieval. The success rate with frozen/thawed embryos is improved when the woman uses hormone replacement instead of her natural cycle. About half or two-thirt of the frozen embryos survive the defrosting process. 
 
 
 
 

10. Other related procedures: 

1) Intracytoplasmic sperm Injection (ICSI) is a technique where the embryologist captures a sperm in a very small glasspipette and inserts it directly into the egg. Many or all the eggs are treated in this manner and the fertilized eggs are monitored for continued growth. The use of intracytoplasmic sperm injection allows a male with an extremely low sperm count or poor motility to fertilize eggs. 

2) Assisted Hatching is another procedure which involves removing the layer of cells from around the fertilized egg to help facilitate implantation by the embryo. It is recommended for women, who have had previously unsuccessful cycles, who are older, or who have elevated FSH levels. 

3) Testicular Sperm Extraction (TESE) is a simple and minimally invasive procedure where a small amount of testicular tissue is removed via a needle biopsy. It is performed under local anesthesia and mild sedation. A sperm is then inserted into each egg using the ICSI procedure. TESE allows for the retrieval of sperm from men who are unable to produce sperm in their ejaculate because of an obstruction or absence of the vas deferens. 

4) Preimplantation Genetic Diagnosis is allows us to identify of genetic disease in the embryo before the embryo implantation (before the pregnancy is establish) and thus eliminates the need for possible pregnancy termination after prenatal diagnosis of a genetically-affected fetus. This new technique marries the recent spectacular advances in molecular genetics and assisted reproductive technology. Five days after fertilization, it is possible to remove 5 or 10 cells from the blastocyst stage embryo without detriment to its further development and these are tested. If the embryo is judged to be free of the disease it can be put back into the uterus.  

The advantages of this test are that it is performed much earlier than the prenatal diagnostic tests, and as only those embryos free of disease will be transferred into the uterus there is only a very small possibility that an affected child will be born. The disadvantages of the procedure are that the woman must undergo in-vitro fertilization so that there are sufficient embryos to examine. 

A frequently raised concern by many couples is that of bearing abnormal children as a result of these procedures. Fortunately, a review of several thousand Blastocyst culture and transfer births has shown no higher incidence of birth defects, or genetic abnormalities, when compared to the population at large. 

11. Couple Participation:

We are well aware that infertility exacts a very heavy toll. The emotional, financial, and physical burden is often overwhelming. It is for this reason that we encourage both partners to be supportive of one another, and participate in the treatment process together. The male partner should make every effort to accompany his partner with every visit. We understand this is not always possible, but it is highly recommended. Cooperation and carefully follow the treatment process will enhance the pregnancy rate.