In vitro fertilization and embryo transfer is commonly referred to as “IVF”. IVF involves removing the eggs and sperm, fertilizing them in vitro under human manipulation, culturing them into embryos, and then implanting them back into the mother’s body, the entire process really only lasts 2-6 days in the test tube. Due to the rapid advances in reproductive technology, such as the birth of new ovulation needles, improved super ovulation methods, the use of transvaginal ultrasound for egg retrieval, major breakthroughs in in vitro fertilization techniques, improvements in in vitro culture techniques, and changes in embryo implantation methods, the technology has become increasingly sophisticated, making IVF one of the most popular forms of assistance for all infertile couples seeking a child.
Intracytoplasmic single sperm injection technique
Single sperm intracytoplasmic injection 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. For those who require this technique, the pregnancy rate is increased.
Indications include.
(i) Those who require sperm retrieval via the testes or epididymis, and men with severe oligospermia usually require ICSI for fertilization;
②People who have failed conventional IVF fertilization may need to be fertilized by ICSI (not absolutely);
③For some couples with unexplained infertility, ICSI can also be considered for fertilization;
(iv) Those with previous history of abnormal fertilization, such as multiple sperm fertilization [1].
Preimplantation embryo genetic diagnosis techniques
Preimplantation genetic diagnosis is an early prenatal diagnosis method that analyzes the genetic material of gametes or embryos before embryo implantation and detects whether the gametes or embryos have abnormal genetic material; through PGD, embryos with normal test items are selected for transfer.
Indications include.
①Sex-linked genetic disorders;
②Single gene related genetic disorders;
③Chromosomal disorders [2];
④ Abnormalities in chromosome number and structure;
(5) High-risk groups who may have children with abnormalities.
I. 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 thawing embryo transfer has become an indispensable method in IVF treatment.
II. The procedure for freeze and thaw embryo transfer is usually as follows.
For women with regular menstruation, the transfer can be done after ovulation, depending on the stage of embryo (oogenesis or blastocyst) at the time of embryo freezing, to determine whether the embryo should be transferred 3 or 5 days after ovulation.
For women with irregular menstruation, the endometrium can be constructed using an artificial cycle. This is usually done by starting 4-6 mg of estradiol valerate orally daily on day 2 of menstruation (or progesterone withdrawal bleeding), monitoring the endometrium after 8-10 days, and starting progesterone administration when the endometrium is ≥8 mm thick, with embryo transfer 4-5 days later. In case of transferring blastocysts, the time of transfer is postponed.
III. Embryo thawing and transfer
The embryos are thawed and frozen on the day of embryo transfer and the transfer procedure is the same as for fresh embryo transfer [3].
IV. Luteal support in frozen-thawed embryo transfer cycles
Luteal support is essential for women who use the artificial cycle method to construct the endometrium, because these women have no follicular growth, no corpus luteum formation and lack of their own secreted progesterone in the body during the artificial cycle, and therefore must rely on exogenous progesterone to support normal endometrial development and embryo implantation.
In women undergoing embryo transfer in a natural cycle, is the application of progesterone support necessary? Some literature reports no difference in pregnancy rates with or without the application of luteal support in this setting, and therefore it is not considered necessary for these individuals.
Embryo-assisted hatching
The human fertilized egg is early encased in the zona pellucida, from which the embryo must hatch before it can be implanted. When the zona pellucida is too hard, too thick, or otherwise impaired in lysis, it can prevent the embryo from hatching, resulting in failure of implantation.
Specific methods of embryo-assisted hatching include.
(i) zona pellucida cutting method;
②Laser perforation by acidic liquid etching: A laser is used 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 with too thick zona pellucida and repeated IVF failures, embryo-assisted hatching can be considered to improve embryo fertilization rate.
IVF Technique Blastocyst Culture
In IVF, blastocyst is the final stage of embryo culture in vitro, which is usually formed on day 5-7 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.
I. Advantages of blastocyst culture and blastocyst transfer
1. Developmental potential of embryos: Whether an embryo can develop to blastocyst is related to its own genes. When an embryo has no developmental potential or carries abnormal chromosomes and genes, it can be eliminated naturally due to its own developmental abnormalities during the extended culture process, and only the best quality embryos can develop into blastocysts.
2. More synchronization between fetal development and endometrium: Blastocyst stage transfer can provide a natural environment closer to reproductive physiology and has a higher implantation capacity.
3. Less risk of multiple pregnancies: Because of the high implantation rate of blastocyst transfer, the number of transferred embryos can be reduced. In case of high quality blastocysts, single blastocyst transfer is advocated, which can low the rate of multiple pregnancies.
4. Embryo culture provides sufficient time for split stage embryo biopsy for preimplantation genetic diagnosis (PGD).
2. Disadvantages of blastocyst culture
1. Embryo culture failure: Blastocyst culture requires high conditions, and due to laboratory culture conditions or embryos themselves, embryos may stop developing or degenerate, resulting in no embryos available for transfer.
2. Waste of more oogenic embryos: Since the in vitro culture environment is not the natural in vivo environment after all, prolonging the culture time may degrade some of the oogenic embryos that can be implanted.
Suitable groups for blastocyst culture
1. Patients who have failed in IVF;
2. Patients with more fetuses: Because of the high implantation rate of blastocyst transfer, it can enable patients to get pregnant as early as possible and save time and energy;
3.When the endometrium and embryo development are not synchronized: in fresh embryo transfer cycle, when the progesterone is significantly elevated before egg retrieval, the endometrium development is not synchronized with the embryo, and blastocyst transfer can correct this asynchrony and improve the pregnancy outcome;
4. Patients who undergo pre-implantation genetic diagnosis.
Suitable groups
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.