The purpose of artificial insemination is to increase the chances of normal sperm reaching the site of fertilization, thus improving the woman’s chances of conception. Depending on the route of insemination, it can be classified as intravaginal, intracervical, intrauterine, intrafallopian, intrafollicular and intraperitoneal. Intrauterine insemination (IUI) is the most commonly used procedure, in which treated sperm is injected into the uterine cavity of a woman, either during the natural menstrual cycle or during the application of low-dose ovulation-promoting drugs. Depending on the source of sperm, it can be divided into IUI with husband’s sperm and IUI with sperm donor. Before performing IUI, couples need to undergo a comprehensive evaluation after appropriate medical and laboratory examinations, including detailed medical history taking, informed consent education, etc. In particular, a hysterosalpingogram should be performed, and the most basic requirement is a patent fallopian tube. I. Indications for artificial insemination
The most common indications for clinical implementation of IUI are mild male oligospermia and/or unexplained infertility.
(i) Mild to moderate semen abnormalities
Mild to moderate oligospermia, weak and abnormal spermatozoa in males. The sperm density should generally be above 10 million/ml, the motility rate (grade a+b) above 25% and the malformation rate below 90%. There is no definite criterion for choosing ICSI or IUI for low sperm quality. It has been reported that the pregnancy rate is significantly lower after IUI with a total sperm count of <10 million in the original semen, while the low limit of total motile sperm count after treatment varies from 3 million, 5 million to 10 million according to different studies .
(ii) Ejaculation disorders
1, anatomical and structural abnormalities of the male genital tract, such as hypospadias, retrograde ejaculation
2. mental and neurological, such as impotence, premature ejaculation, spinal cord injury, etc.
(iii) Unexplained infertility
For the diagnosis of unexplained infertility, it is necessary to determine that the female partner has normal ovulation, the pelvis is normal on laparoscopy, and the male partner has normal semen analysis twice. The data found that the pregnancy rate in couples with IUI increased by an average of 6.1% compared to couples with ovulation guidance alone, while the pregnancy rate in the latter increased by only 3.9% compared to the pregnancy expected without intervention.
(iv) Cervical factors
Thick or scanty cervical mucus, including after electro-ironing or cryotherapy for cervicitis and after cervical conization.
(v) Abnormalities of the female genital tract
Vaginal cervical stenosis, vaginal cramps during intercourse, etc.
(vi) Immunological factors Positive anti-sperm antibodies
(vii) Endometriosis Mild to moderate endometriosis
(viii) Ovulation disorders (PCOS)
This includes WHO type I and type II ovulation disorders. For patients with ovulation disorders, ovulation promotion guided intercourse for 3-6 cycles may be preferred before considering artificial insemination after failure. Also, as a form of male fertility preservation, it has gained wide acceptance for male oncology patients to freeze their sperm prior to treatment and resuscitate it for IUI when needed. Severe abnormalities of male sperm are the most common indications for donor insemination.
(i) Non-obstructive azoospermia
These include spermatogenic disorders, congenital testicular dysplasia, and Crohn’s disease.
(ii) Severe semen abnormalities
These include obstructive azoospermia, severe oligo-, hypo- and malformed spermatozoa, etc. However, it is actually possible for all such patients to obtain offspring using their own sperm through intracytoplasmic single sperm microinjection (ICSI) in oocytes. However, the cost of ICSI treatment may make it unaffordable for some patients to opt for donor insemination. For this group of patients, a fully informed conversation should be held prior to treatment to inform them of the opportunity to obtain their own blood relatives’ offspring, allowing the couple to consider the situation holistically.
(iii) Family or hereditary diseases of the male partner
Such as hemophilia, Huntington’s disease, etc. Such patients can also be screened for certain genetic disorders through pre-implantation genetic diagnosis (PGD) and can also obtain healthy offspring with their own sperm.
II. Implementation of artificial insemination procedure
Artificial insemination can be performed during natural cycles or ovulation cycles. Currently, donor insemination tends to use the natural menstrual cycle, while husband insemination tends to use the ovulation-promoting cycle.
(i) Natural menstrual cycle insemination
The female partner has a regular menstrual cycle and the growth of follicles and endometrium should be monitored continuously from the 10th-12th day of menstruation. If the diameter of the dominant follicle reaches 17-19mm and urinary LH is positive, IUI will be considered 12-24 hours later. if urinary LH is negative or lack of sufficient LH peak to induce ovulation, HCG 5000iu can be injected to induce ovulation as appropriate and IUI will be performed 28-36 hours later. progesterone will be applied for luteal support after the procedure and pregnancy will be detected 15 days later.
(ii) IUI in pro-ovulatory cycle
The application of ovulation-promoting drugs can increase the number of developing follicles and improve the chances of conception, but complications such as ovarian hyperstimulation syndrome (OHSS) and multiple pregnancies can also occur. Therefore, ovulation-promoting drugs should be limited to the lowest effective dose during the IUI cycle.
The following ovulation-promoting regimens are currently in use.
1. Clomiphene citrate + gonadotropin + human chorionic gonadotropin;
Clomiphene is the first line of ovulation promotion, starting on the 3rd-5th day of menstruation, 50mg/day for 5 days. The potential antiestrogenic effects of CC may cause endometrial dysplasia and cervical mucus thickening, and supplementation with estradiol valerate (Tegretol) 1-2 mg/day is indicated until pregnancy is confirmed by urine test 14 days after IUI. Because of the antiestrogenic effect of clomiphene, the high E2 level produced by follicles has a weak positive feedback effect on pituitary gland, and the endogenous LH peak formation is not high enough to cause ovulation obstruction, so hCG must be added in clomiphene ovulation cycle, while hCG is added in gonadotropin-only ovulation cycle as appropriate to control ovulation time.
2. Letrozole + Gn + hCG
Letrozole is an aromatase inhibitor that overcomes the side effects of clomiphene. Letrozole 2.5mg/day orally on day 3-5 of menstruation for 5 days. hMG can be used as human menopausal gonadotropin (hMG), which should be started from 75iu/day for 3-5 days, and the maximum dose should not exceed 150iu/day.
3. Gn+ hCG
Urotrophin 75iu/day should be started on the 5th day of menstruation and injected intramuscularly for 4 days to observe the follicular development, and then continued or increased to 150 iu/day as appropriate. During ovulation, the follicle diameter should be monitored by ultrasound and hCG should be injected at the right time. 2000-6000 IU of hCG should be injected intramuscularly or 250ug subcutaneously when the diameter of the dominant follicle is ≥18mm. If many follicles are found, gonadotropin-releasing hormone agonist (GnRHa) can be used to stimulate the endogenous LH peak to induce ovulation, and treprostinil (Dabigia) 0.1mg subcutaneous injection can be used instead of hCG to induce final maturation of follicles and ovulation, which can achieve the purpose of ovulation and avoid the effect of hCG induced OHSS.
III. Selection of the timing of artificial insemination
The timing of artificial insemination injection of sperm should be chosen as close to the time of ovulation as possible. The main methods to determine ovulation at an early stage are basal body temperature measurement and the change of cervical mucus properties, but their accuracy is low. Vermesh et al. reported that urine LH test strips can predict ovulation in 84% of cases, but due to the presence of luteinized unruptured follicles, ultrasound monitoring of follicular rupture is the absolute determinant of ovulation. In China, a positive urine LH test indicates that ovulation will occur within 24 hours. Therefore, if a positive urine LH test is found in a natural cycle, insemination should be performed within 24-36 hours. In the ovulation cycle, hCG is injected intramuscularly when the dominant follicle reaches 18 mm in diameter. Follicular rupture occurs within 34-46 hours, with an average of 38 hours, so most centers place the timing of IUI at 34-38 hours after hCG injection. Some centers routinely perform two inseminations in a cycle, one before and one after ovulation, but no studies have confirmed a difference in pregnancy rates between one and two inseminations .
IV. Sperm preparation for artificial insemination
The freshly ejaculated semen is collected by masturbation into a sterile sperm collection cup on the day of sperm collection, and the patient is informed to avoid contamination. If previous examinations suggest high sperm density and low semen volume, appropriate amount of culture fluid can be added to the sperm retrieval cup beforehand, and for low sperm density, sperm can be retrieved 1 hour later in a second time to increase the number of effective sperm. For men with retrograde ejaculation, 4g of sodium bicarbonate tablets are taken in 500ml of water the night before sperm extraction; on the day of sampling, another glass of water containing 4g of sodium bicarbonate is drunk to alkalize the urine. Immediately after emptying the bladder, ejaculate through the masturbation method, and at the end of ejaculation, urinate again into a sterile container, and the sperm in the urine can be collected by centrifugation.
The collected semen is placed in a 37°C water bath to liquefy and once liquefied it is ready for processing. Before performing IUI, the sperm must be washed and processed to remove the seminal plasma and to preferentially select the sperm. This is because: prostaglandins in seminal plasma injected into the uterine cavity can cause uterine contractions and severe pain, while unprocessed semen injected directly into the uterine cavity and then into the pelvic cavity carries the risk of causing pelvic infection.
The goal of treating semen is to enrich the largest number of morphologically normal motile sperm in a small culture with seminal plasma, white blood cells and bacteria removed.
The more commonly used method of semen processing is the upstream method. The procedure is as follows: take several test tubes and add 2 ml of sperm culture fluid to each tube. Then slowly add 0.5 ml of liquefied semen to the bottom of each tube to form two interfaces. Cover with a cap, tilt at 45° and place in a 37°C, 5% CO2 incubator for 30-60 minutes. Collect the supernatant of each tube, centrifuge 200 g×5 min, discard the supernatant and then add 2 ml of culture solution, mix well and centrifuge 200 g×5 min. The precipitate was left and 0.5 ml of culture medium was added to make a sperm suspension, and the sperm concentration was adjusted to 10-30×106/ml and set aside. The upstream method uses the ability of spermatozoa to swim across the liquid interface into different cultures, and achieves separation from dead sperm, agglutinated sperm, deformed sperm and cellular impurities on its own. The sperm vitality and viability obtained are high, reaching more than 90%.
V. Operation of artificial insemination
The operation of IUI is relatively simple. The key points are asepsis, gentleness, avoiding infection and stimulation of the endometrium, leading to spasm and the adverse effect of bleeding on sperm survival. The operation is performed with the patient in a bladder amputation position and the vulva, vagina and cervix are wiped with saline. The treated sperm fluid is drawn into the insemination catheter, which is placed into the uterine cavity to a depth that exceeds the endocervix, and the sperm fluid is slowly injected and left for a few moments before retiring the catheter. If difficulties are encountered in placing the outer cuff, a rigid IVF-ET tube can be used to help adjust the bend and then place the outer cuff before placing the inner tube with semen. Try not to touch the bleeding. On the second day after the procedure, observe whether the follicle is expelled or not, and if the follicle is not expelled, perform another IUI. If ovulation has occurred, progesterone gel pills Angiotensin 100mg, Bid, can be applied for 15 days.
For the choice of different insemination tubes, easy operation and less damage are preferred. 2006, a scholar compared the pregnancy rate after operation of four commonly used insemination tubes, namely wallance? embryo transfer tube, IUI tube and cook? and Gynetics? insemination tube. Of these, all were tubes except the wallance? embryo transfer tube, which was a rigid tube. There was no significant difference between the various insemination tubes in terms of bleeding during the pregnancy outcome operation, but the patient’s comfort level was clearly better with the tube.
The total amount of sperm fluid injected into the uterine cavity is 0.2-0.5 ml for conventional intrauterine insemination, and in the case of intrafallopian insemination, the total amount is about 4 ml, which is the amount needed to get to the point of ensuring that the sperm fluid reaches the fallopian tubes and even partially flows into the pelvis. Therefore, intrauterine insemination is the most appropriate when performing insemination after recovery of frozen sperm, due to the limited amount of sperm fluid.
VI. Complications of artificial insemination
(1) Ovarian hyperstimulation syndrome
There is a risk of OHSS when insemination is performed during the ovulation promotion cycle. Therefore, when performing ovulation promotion, the ovarian responsiveness of the patient should be fully evaluated. For patients with high risk of OHSS, such as PCOS, young and thin body type, ovulation promotion with the first-line drug clomiphene is still advocated, and if additional gonadotropins are needed, ovulation should be performed in a small, slowly increasing dose regimen. Once there is a tendency of OHSS, HCG injection should be avoided to induce ovulation and GnRHa should be used to stimulate endogenous LH peak to induce ovulation, and it is recommended to cancel the IUI cycle and pay attention to contraception.
(2) Pelvic infection
As an intrauterine operation, IUI carries the risk of pelvic infection. For example, contamination during semen collection or processing, and vaginal inflammation in the female patient herself. Therefore, during the handling of semen for IUI and when performing intrauterine sperm injection, the operation should be strictly aseptic, and those with vaginitis must be cured of vaginitis before performing IUI.
(3) Bleeding and injury
IUI is a simple operation and usually does not cause injury, but some patients with difficult intubation may easily cause bleeding. A small amount of intracervical bleeding will not affect the outcome of insemination for pregnancy, but if there is a lot of bleeding in the uterine cavity, it will lead to a decrease in insemination effect. Therefore, care should be taken to operate gently during IUI and to select a suitable insemination tube for the operation. For patients with excessive uterine flexion, cannulation can be performed under ultrasound guidance after filling the bladder to avoid bleeding and injury caused by blind insertion.
(4) Multifetal pregnancy
In IUI cycles with ovulation promotion, multiple eggs develop and are expelled increasing the risk of multiple pregnancies. The ideal number of developing follicles in an IUI ovulation cycle should be 1-2. If the number of developing follicles exceeds 3, the patient should be advised to abandon treatment to avoid multiple pregnancies.
VII. Pregnancy outcome of artificial insemination
For pregnancy outcome of IUI, there is a wide variation in different reports. The average pregnancy rate is around 10-12% for frank sperm IUI and 15-20% for donor sperm IUI. In addition, the pregnancy rate of IUI also varies between different etiologies and ovulation protocols. Patients with unexplained infertility and cervical factors have relatively high pregnancy rates, while patients with endometriosis have the lowest pregnancy rates with IUI. In ovulation protocols, gonadotropin use does not significantly improve pregnancy rates, but multiple birth rates are significantly higher, so clomiphene remains the first-line agent for ovulation promotion in IUI cycles.
Due to pregnancy rates and cost of IUI cycles, patients often undergo multiple cycles of repeat therapy, and there are differences between centers in how many IUI cycles are routinely followed by a switch to IVF. According to a study by Custer et al, the pregnancy rate decreases significantly after the sixth IUI treatment cycle to less than 5% . Patients should generally be advised to change to IVF after 2-3 cycles of IUI without pregnancy.
VIII. Factors affecting the pregnancy rate of IUI
(1) Age of the infertile couple.
The pregnancy rate of IUI cycles decreases when the age of the couple increases, especially when the female partner is over 38 years old. Plosker et al. reported that the fertility of women aged 24-39 years had a cycle fertility of 0.11-0.14 compared to 0.04 for women aged 40 years or older. The pregnancy rate for donor IUI was 18.9% for women under 40 years of age and only 9.2% for women over 40 years of age. In addition, although the effect of male age on sperm density and viability is not obvious, sperm function and chromatin integrity will be affected and reduce the chance of conception.
(2) Years of infertility
As the number of years of infertility increases, the pregnancy rate of IUI cycles decreases. The effect of the number of years of infertility on the pregnancy rate even exceeds that of the age factor, and the pregnancy rate of women with more than 5 years of infertility is significantly lower than that of women with less than 5 years of infertility.
(3) Causes of infertility
Among the indications for IUI, the cycle pregnancy rate is higher in patients with female cervical infertility, followed by those with unexplained infertility, and lower in those with male factor. Cumulative pregnancy rates of 43% have been reported in patients with cervical factors alone, and natural cycle IUI is recommended in these patients to avoid a high rate of multiple pregnancies. In addition, pregnancy rates are higher in patients with ovulatory disorders and lower in patients with endometriosis. In 2 retrospective studies of donor IUI, the pregnancy rates in patients with endometriosis AFS score stage I/II were 2% and 6.5%, respectively, which were significantly lower than those in the control group of 11.5% and 14%. The reason for this is mainly that kinins and growth factors secreted by endoheterozygous lesions interfere with ovulation, fertilization, embryo development and implantation.
(4) Sperm parameters
In patients with male factor IUI, sperm motility and percentage of normal spermatozoa are important indicators of fertility among semen parameters.Miller et al. reported a pregnancy rate of 12.4% for IUI in patients with a total motile spermatozoa (TMS) of 20 million after treatment and 7.4% for those with 10-20 million motile sperm.Kamath et al. found that motile spermatozoa in the original semen were between 5 and 14%. Kamath et al. found that the pregnancy rate for IUI was only 2.7% when the motile spermatozoa were below 5 million/ml, and that the ideal treatment cycle was one with 10-20 million motile sperm/ml. In addition, the pregnancy rate of IUI decreased from 18.2% to 4.3% when the sperm malformation rate exceeded 90%.
IX. Other related discussions
1. Luteal support in IUI cycles
There has been no clear conclusion on the need for luteal support in IUI cycles. If two or more follicles develop in an ovulatory cycle, the luteal secretion of estrogen and progesterone after ovulation is higher than in a natural cycle, which causes an increase in inhibin A, which suppresses LH and FSH levels. As early as 1995, it was hypothesized that low levels of LH would lead to luteal function defects, as evidenced by low progesterone levels or a shortened luteal phase. According to the recommendations published by Ragin et al. in 2001, luteal support is not necessary after natural cycles or mild ovarian stimulation (1-2 follicle development) IUI, if the patient has no clear evidence of previous luteal insufficiency. There are no clinical controlled studies supporting luteal support after IUI ovulation promotion, so the majority of centers use luteal supplementation after IUI as a routine, more customary than necessary. At the time of luteal supplementation, either hCG or progesterone is an option, but it should be noted that hCG injection may increase the chance of OHSS as well as cause false positives on pregnancy tests.
2.Withdrawal of IUI cycle
There are 2 main reasons for abandonment of IUI cycles: small follicle ovulation and multiple follicle development. It is generally accepted that follicles that disappear below 15 mm in diameter contain poorly developed eggs and have a very low chance of conception, and this is especially likely to occur in patients of advanced age or with reduced ovarian function. Therefore, patients are advised to abandon the current cycle when small follicles are present in either natural or ovulation-promoting cycles. If small follicular ovulation occurs in 2-3 consecutive cycles of natural cycle monitoring, the ovulation promotion regimen should be changed. It has been reported that early onset LH peaks occur in about 25-30% of IUI ovulation promotion cycles. At this time, the use of the previous cycle’s luteal phase GnRHa continuous pituitary depot injection regimen can avoid early ovulation due to early onset of endogenous LH peaks, but the pregnancy rate does not improve, and it has been postulated that early onset LH peaks are actually a manifestation of low quality of developing follicles. In addition, the use of GnRH antagonists to suppress early onset LH peaks during the IUI ovulation cycle did not significantly improve pregnancy rates. A combination of results from seven clinically randomized controlled studies found only a 5% increase in pregnancy rates in the GnRH antagonist group compared to the conventional ovulation promotion group. The risk of multiple follicular development in the ovulation cycle poses a potential risk of OHSS and multiple pregnancies, which can be managed in three ways: abandonment of the cycle, early puncture of the extra follicles, or IVF, as some centers abroad have stricter criteria for abandoning IUI cycles due to the risk of multiple pregnancies, with two or more follicles >14 or 15 mm in diameter. Early puncture of extra follicles is usually done on the day of the proposed hCG injection in patients with serum estradiol ≤1500 pg/ml and no tendency to OHSS, and after adequate conversation to inform about the risks, the extra follicles can be punctured at the discretion of the patient, and only 1-2 maximal follicles can be kept before hCG injection to avoid multiple pregnancies. Considering the cost of IVF, the risk of pelvic puncture, etc., it is not advocated to change to IVF at present, except for a few patients with PCOS who have ovulation multiple times and have follicles with very close threshold of response to gonadotropins and no dominant follicle growth, small follicles can be retrieved and changed to IVM.
3. Choosing between IUI and IVF
Some couples with infertility may have difficulty in choosing between IUI and IVF, especially those with unexplained infertility. As a specialist, you should help your patients make the most appropriate recommendation and choice based on sufficient clinical evidence. The following clinical evidence can be used as a basis for choice.
(1) Natural cycles of IUI do not increase the chances of pregnancy in couples with unexplained infertility.
(2) Pregnancy rates for clomiphene/IUI cycles range from 5-10%, with similar pregnancy rates within 6 cycles.
(3) Application of Gn ovulation promotion may bring about OHSS.
(4) IVF increases the chance of pregnancy by 6-fold compared to IUI in those with unexplained infertility.
(5) ICSI is more suitable than IUI for severe male infertility.
Most specialists now prefer that couples who are infertile after 4-6 cycles of IUI should be re-evaluated and considered for IVF. In a study by Reindollar et al. 2007, two clinical strategies are compared, one is to start with 3 cycles of clomiphene IUI followed by 3 cycles of gonadotropin IUI and switch to IVF if still infertile; the other strategy is to proceed directly to IVF after 3 cycles of clomiphene IUI, with cumulative clinical pregnancy rates of 65% and 64% for the two strategies, respectively The cumulative clinical pregnancy rates for the two strategies are 65% and 64%, respectively, but the latter shortens the time to conception and reduces costs. In addition, the age of the female patient is also an important reference factor. The birth rate after IUI treatment in women over 40 years of age with unexplained infertility is less than 5%, whereas the birth rate obtained with IVF assisted conception can reach 15%, so IVF should be considered as early as possible for women of advanced age without the need to repeat multiple IUIs.
Overall, the choice of IUI or IVF, or the timing of IUI to IVF, should be based on a combination of patient age, years of infertility, the presence of clear factors unfavorable to pregnancy, financial ability, and other conditions, in order to obtain a higher pregnancy rate in a shorter period of time and at a lower cost.