In vitro fertilization and embryo transfer (IVF-ET) is often called “in vitro fertilization” in our country. In fact, in vitro fertilization is a special technique in which both eggs and sperm are taken outside the body and allowed to complete the fertilization process in an artificially controlled environment outside the body, and then the early embryos are transferred to the woman’s uterus, where they are conceived as a child. The babies produced using in vitro fertilization techniques are called IVF, and these children also grow up in the mother’s womb. It can be said that “IVF technology” is equivalent to “in vitro fertilization”. Indications 1. Patients with tubal obstruction; 2. Patients with unexplained infertility who have failed to conceive through IUI and other treatments; 3. Patients with severe oligospermia in the male partner or azoospermia in the male partner who need to obtain sperm through testicular or epididymal puncture; 4. Women with endometriosis and infertility can use IVF to help them conceive as appropriate; 5. Patients with ovulation disorders who have no mature follicles after general ovulation treatment. Classification 1. conventional in vitro fertilization and embryo transfer techniques; 2. intracytoplasmic single sperm injection techniques; 3. preimplantation embryo genetic diagnosis techniques. Procedure 1. Ovulation treatment Since not every egg can be fertilized and not every fertilized egg can develop into a viable embryo, multiple eggs have to be obtained from the woman’s body to ensure that there are embryos that can be transferred, which requires ovulation treatment for the woman. 2. Egg retrieval The doctor applies a special egg retrieval needle under ultrasound guidance to puncture the mature follicles vaginally and aspirate the eggs. Egg retrieval is usually performed under intravenous anesthesia, so the woman does not feel the pain caused by the puncture procedure. 3. In vitro fertilization Sperm acquisition: While the woman is having her eggs retrieved, the man performs the sperm retrieval. After the semen has undergone a special washing process, the sperm and eggs are placed in a special medium with a view to natural union. This is called conventional fertilization method. 4. Embryo transfer A few days after fertilization, a very thin embryo transfer tube is applied and the best embryos are transferred into the mother’s uterus through the cervix. The number of embryos to be transferred is decided according to age, embryo quality and previous IVF outcomes, usually 2 to 3 embryos are transferred. In recent years, in order to reduce the rate of multiple pregnancies, some centers have opted for single embryo transfer, or a maximum of 2 embryos. Since the embryo transfer tube is very thin and the doctor moves gently, the patient usually does not experience any pain. 5. Luteal support Due to the application of GnRH agonists/antagonists and ovulation-promoting drugs, as well as the loss of follicular granulosa cells due to egg retrieval, women usually have luteal insufficiency during the egg retrieval cycle, requiring luteal supplementation/support with progesterone and/or chorionic gonadotropin. If there is no pregnancy, discontinue progesterone and wait for the onset of menstruation. If pregnancy has occurred, continue progesterone application, usually until 3 weeks after the fetal heart is seen on ultrasound. 6. Determination of pregnancy Serum HCG is measured 14 days after embryo transfer to determine if pregnancy is present. Serum HCG will be measured again 21 days after embryo transfer to see how the embryo is developing. Transvaginal ultrasound at 30 days after embryo transfer to determine if intrauterine pregnancy is present and if there is fetal heartbeat. Success rate The success rate of IVF-ET technique treatment is generally determined by the clinical pregnancy rate, which is the proportion of clinical pregnancy cycles to embryo transfer cycles, and clinical pregnancy is defined as the intrauterine gestational sac observed by vaginal ultrasound 28-30 days after embryo transfer. Success rates vary among IVF centers, with most centers achieving success rates of 30% to 50% per transfer cycle and some reporting success rates of 60% to 70% per transfer cycle. Clinical treatment success rates are influenced by a variety of factors, such as patient selection, clinical treatment methods, and laboratory techniques. Factors affecting the success rate of IVF There are many factors that affect the success rate of IVF. The age of the woman, the etiology of infertility, and the quality of the laboratory at the IVF center are all factors that affect the success rate. Age is an important factor affecting the success rate of IVF, as age increases, the number of eggs decreases, the quality decreases, the fertilization rate decreases, the pregnancy rate decreases significantly, and the miscarriage rate increases. the pregnancy rate of IVF for women aged 41 to 42 years is 12%, the live birth rate of embryos per transfer for women over 42 years is only 5 or 9%, and the miscarriage rate for women over 43 years is 50%. 2. Hydrocele in the fallopian tube significantly reduces the embryo implantation rate and pregnancy rate, resulting in a 50% decrease in pregnancy rate. Therefore, women with hydrosalpinx should have their tubes removed before IVF. 3. Uterine abnormalities such as endometrial polyps, endometritis, previous surgery or inflammation (tuberculosis is the most common) resulting in damage to the endometrium can affect embryo implantation. Complications Overall, IVF technology is safe, but some complications may occur. 1. Ovarian hyperstimulation syndrome (OHSS) Due to the growth of multiple follicles, some factors in the body are altered, causing fluid to leak from the blood vessels into the abdominal cavity or even the chest cavity, resulting in thoracoabdominal fluid. The incidence is about 10%. Most people have mild symptoms, manifesting as abdominal distension, abdominal discomfort and mild nausea, which can be left untreated; however, a few people will have severe abdominal distension, oliguria, abdominal pain, poor nausea, and even chest tightness and shortness of breath, at which time they need to be given intravenous rehydration or even admitted to hospital for treatment. In less than 1% of cases, blood clots or renal failure may occur. 2. Side injuries caused by egg retrieval ① Bladder injury, patients can develop hematuria, which can usually be stopped by indwelling a urinary catheter and performing bladder irrigation. (ii) Occasionally, the intestinal canal or blood vessels in the pelvis may be punctured. ③Ovarian bleeding: In a few cases the punctured ovary will continue to bleed, sometimes even requiring open abdomen to stop the bleeding. ④Pelvic infection 3. Ovarian torsion Multiple follicles grow as a result of ovulation promotion treatment or multiple luteal cysts form after egg retrieval, causing the ovaries to enlarge significantly, at which point ovarian torsion can result when the woman is overactive or changes position too rapidly. Patients may experience sudden and severe abdominal pain, which may be accompanied by nausea and vomiting. If the twisted ovary cannot be reset in time, surgical treatment may be required, and in severe cases, the necrotic ovary may need to be surgically removed. 4. Multiple pregnancy The rate of multiple pregnancies due to IVF technology is significantly higher than that of natural pregnancies because of the transfer of multiple embryos to the uterus, which is about 25-30%. The risk of late miscarriage and preterm delivery is significantly higher in multiple pregnancies than in singleton pregnancies, and the risk of gestational diabetes, gestational hypertension, obstructed labor and postpartum hemorrhage is significantly higher in mothers. Therefore, multiple pregnancies are detrimental to both mother and child. Many IVF centers are now reducing the number of embryos transferred or performing single embryo transfers to reduce the rate of multiple pregnancies. For three or more pregnancies, reduction is mandatory, while for twin pregnancies, patients are advised to reduce the number of embryos. 5. Ectopic pregnancy The incidence of ectopic pregnancy in the general population is 1% to 2,5%. Although IVF involves the transfer of embryos into the uterus, due to the influence of tubal chemokines on the embryos, the embryos can wander into the fallopian tubes, where they can implant and develop, resulting in ectopic pregnancy. Sometimes the embryo will also implant in the cervix and other areas. Therefore, IVF treatment does not prevent the occurrence of ectopic pregnancy; on the contrary, the incidence of ectopic pregnancy in women undergoing IVF treatment is higher than in the general population, ranging from 2% to 4%. Safety of the offspring produced by IVF technology. Specific methods 1. intracytoplasmic single sperm injection technique Intracytoplasmic single sperm injection (ICSI) is a special form of fertilization that accompanies IVF, a technique in which a single sperm is injected directly into the egg cell to assist in fertilization, abbreviated as ICSI. but even though the sperm is injected directly into the egg cell, fertilization is still not guaranteed. For those who require this technique, the pregnancy rate is increased. Indications include: ① those who need sperm retrieval via the testes or epididymis, and men with severe oligospermia usually need ICSI for fertilization; ② those who have failed previous IVF conventional fertilization may need to be fertilized by ICSI (not absolutely); ③ for some couples with unexplained infertility, ICSI can also be considered for fertilization; ④ those with a previous history of abnormal fertilization, such as multiple sperm fertilization. Preimplantation genetic diagnosis (PGD) is an early prenatal diagnosis method to analyze the genetic material of the gametes or embryos before embryo implantation to detect whether the gametes or embryos have abnormal genetic material; through PGD, embryos with normal testing items are selected for transfer. The indications include: ①sex-linked genetic disorders; ②monogenic related genetic disorders; ③chromosomal disorders; ④chromosome number and structure abnormalities; ⑤high risk groups who may give birth to abnormal children. 3. Embryo freezing and freeze-thaw embryo transfer Freezing of excess embryos for later transfer can increase the cumulative pregnancy rate of IVF and can result in significant cost savings. Sometimes all embryos are frozen when there is a serious risk of OHSS, or when embryo transfer is not advisable for other reasons. Therefore, embryo freezing and embryo thawing transfer have become indispensable methods in IVF treatment. 4. Repeated embryo implantation failure in IVF There are many reasons for repeated embryo implantation failure, some of which are not clear. Treatment that may be helpful includes: ① checking the karyotype of both partners; ② performing hysteroscopy to exclude uterine cavity abnormalities, such as the presence of endometrial polyps; endometrial biopsy to check for endometritis (pathology); ③ endometrial blood flow measurement: some literature reports that the pregnancy rate in those with endometrial blood flow deficiency (iv) if hydrosalpinx is present, the hydrosalpinx must be removed; (v) in some patients, embryo-assisted hatching may increase the chance of embryo implantation; (vi) blastocyst transfer: the pregnancy rate of blastocyst transfer is higher than that of oogenesis embryo transfer. 5. Embryo-assisted hatching The human fertilized egg is encapsulated in the zona pellucida early in life, and the embryo must be hatched from the zona pellucida before it can be implanted. When the zona pellucida is too hard, too thick, or otherwise obstructs the lysis of the zona pellucida, it can prevent the embryo from hatching, resulting in failure of implantation. Specific methods of embryo-assisted hatching include: (1) zona pellucida cutting; (2) acidic liquid etching; and (3) laser perforation: the application of a laser to make a hole in the zona pellucida or to thin the zona pellucida. Women of advanced age are prone to sclerosis of the zona pellucida. For women aged ≥38 years old, with too thick zona pellucida and repeated IVF failure, embryo-assisted hatching can be considered to improve the embryo implantation rate. 6. Blastocyst culture In IVF, blastocyst is the final stage of embryo in vitro culture, which is usually formed on the 5th to 7th day after egg fertilization. In its natural state, the human embryo is implanted into the mother in the form of a blastocyst. Therefore, it is not difficult to understand that blastocyst transfer is performed to obtain a high rate of embryo implantation.