Where should the “test tube baby” go? Part 1: “Transplantation”

There are two ways to place high-quality embryos: cryopreservation and transplantation. Today we will talk about transplantation.

Under normal physiological conditions, the embryo will develop into the morula and blastocyst stage 4 to 5 days after ovulation and enter the uterus and implant successfully. Implantation refers to the process of the embryo invading the endometrium through interaction with the endometrium. Only when the embryo implants successfully can it indicate the success of conception. Embryo transfer is the last step in the birth of a "test tube baby" and it is also a very important step. Therefore, a delicate embryo transfer is crucial to the success of IVF.

Embryo transfer is performed under the guidance of abdominal B-ultrasound. The doctor determines the direction of the transfer tube and the appropriate embryo placement position, and uses a fine transfer tube to implant the embryo into the uterine cavity. This operation is simple and fast and can be completed in 2 to 5 minutes. Depending on whether the transplanted embryo is a fresh embryo (embryo formed during the egg collection cycle) or a frozen embryo (embryo that has been vitrified and revived), the transplant is divided into fresh transplant and frozen revived transplant.

Fresh embryo transfer is routinely performed 3, 5 or 6 days after egg retrieval. High-quality cleavage-stage embryos on the 3rd day or high-quality blastocysts on the 5th or 6th day are selected for intrauterine transfer. Fresh transfer can avoid embryo damage that may occur during the freezing and thawing process, and reduce the patient's medication and costs. Since the ovaries are in a state of overstimulation after the ovulation cycle, the success rate of fresh transfer is slightly lower.

Cryo-thaw transfer is also commonly known as "frozen embryo" transfer (FET). Whether the patient's frozen embryos are in the cleavage stage (third day) or the blastocyst stage, they are all called "frozen embryos". Frozen embryos "hibernate" in liquid nitrogen at -196℃. They need to be "awakened" before they can be transplanted. This "awakening" process is called recovery. The embryo cells "hibernating" in liquid nitrogen are in a hypertonic state. After being taken out of liquid nitrogen, they are immediately placed in a recovery solution containing a non-permeable cryoprotectant that forms a hypotonic environment. Through the recovery solution from high to low concentrations, the embryo cells gradually return to an isotonic state, thereby "awakening" the embryo. After the embryo is awakened, it can be transplanted after being cultured in vitro for more than 2 hours. With the improvement of the level of assisted reproductive technology, the proportion of frozen-thaw embryo transplantation has gradually increased. Advantages of frozen-thaw technology: 1. It can reasonably limit the number of transplanted embryos and reduce the rate of multiple pregnancy; 2. It provides patients with embryo transplantation failure or miscarriage with the opportunity for re-transplantation; 3. At present, the country advocates the second and third child policy. The frozen-thaw transfer technology can preserve the fertility of excess embryos and save the patient's treatment costs.

Factors affecting transplantation include age, cycle number, number of transplanted embryos, serum E2 level, progesterone level on the day of HCG injection, hydrosalpinx, endometriosis, etc. These factors can reduce the quality of eggs or endometrial receptivity and affect the clinical success rate of transplantation. In addition to the above female factors, poor sperm quality of the male partner and abnormal chromosomes of eggs or sperm can also affect the clinical pregnancy rate and live birth rate. At the same time, on the day of the transplantation operation, the doctor will instruct the patient on how to use the medication, and on the 14th day, come to Ji'ai to draw blood to test the blood HCG value to determine whether the patient is pregnant. The doctor will guide the subsequent medication based on the blood report. If you are out of town or for other reasons and cannot come to Ji'ai for a blood test, you can go to the nearest medical examination and call the attending physician of the outpatient clinic for follow-up treatment and medical advice.

Here are some simple questions to answer:

Is there a difference in the success rate of fresh transplants and frozen-thaw transplants?

A: No, many studies have shown that the success rate of cryopreservation transplantation is higher than that of fresh transplantation. With the advancement of cryopreservation technology, the rate of whole embryo freezing cycles in reproductive centers is increasing day by day. However, fresh transplantation can avoid freezing damage caused by low embryo quality and reduce the financial burden on patients.

Do embryos at different stages of development have the same success rate for transplantation?

A: Different. Clinically, there are different embryo transfer cycles. The most commonly used ones are D3 cleavage-stage embryos and D5 or D6 blastocyst-stage embryos. The success rate of blastocyst-stage embryo transfer is higher than that of cleavage-stage embryos. However, in an egg retrieval cycle, the formation rate of high-quality cleavage-stage embryos is 50-60%, and the formation rate of blastocysts is 20-30%, so blastocyst culture will increase the cycle cancellation rate and transplant cancellation rate. It is hoped that patients will follow the doctor's advice and choose individualized embryos of the appropriate period for transplantation.

Does it mean that the more embryos are transplanted, the higher the pregnancy rate?

A: Not really. Retrospective data analysis found that transplanting more than two embryos does not increase the pregnancy rate, but increases the risk of multiple pregnancies. The goal of ART assisted reproductive treatment is to give birth to a single, full-term, healthy baby, minimize twin pregnancies, and eliminate the risk of triplet pregnancies.

Is embryo transfer painful? Do I need anesthesia?

Answer: The embryo transfer process is a very gentle operation with very little pain, so no anesthesia is required.

Do I need to take leave or stay in bed after the transplant?

A: No need to stay in bed. Experts recommend that patients lead a normal life after embryo transfer, pay attention to diet (eat more vegetables and protein-rich foods), maintain a good mental state, and reduce strenuous exercise. Come to the hospital 14 days after the transfer to determine whether you are pregnant by testing the blood HCG content. The doctor emphasized that you should not stop taking the medicine on your own before taking a blood test for HCG to confirm whether you are pregnant.

Can IVF be used to customize twins?

A: No, IVF twins are related to the number of embryos transplanted. The consensus of domestic experts is that "the number of embryos transplanted per transplant cycle is ≤ 2". The transplanted embryos may all survive and implant, or they may not survive. Therefore, 1 to 2 embryos are transplanted, and how many embryos survive and implant in the uterus is a matter of probability. However, twin or multiple pregnancies may cause some complications, such as anemia, hypertension, premature birth, low birth weight and postpartum hemorrhage, which threaten the health of mother and baby, or even life.

Can IVF customize the gender of the child?

A: IVF cannot customize the gender of the child, which is illegal in China. If the patient has a sex chromosome genetic disease, pre-implantation prenatal diagnosis technology is necessary to obtain a healthy child.