In Vitro Fertilization: History, Terminology, Medical Uses, Rate of Success, Complications and Methods

This method is mainly tried if less invasive or expensive options have failed or are unlikely to work.


The first successful birth of a child after in vitro fertilization treatment, Louise Brown, occurred in 1978. Louise Brown was born due to a natural in vitro fertilization cycle where no stimulation was done.

The procedure was carried out at Dr. Kershaw’s Cottage Hospital (now Dr. Kershaw’sHospice ) in Royton, Oldham.

Robert G. Edwards received the Nobel Prize in Physiology or Medicine in 2010, the physiologist who co-developed the treatment along with Patrick SteptoeSteptoe was not eligible for consideration since the Nobel Prize was not awarded posthumously.

With the donation of ovules and in vitro fertilization, women who have already passed their reproductive stage, have infertile male partners, have idiopathic fertility problems, or have reached menopause, can become pregnant.

Adriana Iliescu had the record of being the oldest woman to give birth through in vitro fertilization and donated ovum when she gave birth in 2004 at the age of 66, a form approved in 2006.

Some couples can become pregnant after in vitro fertilization treatment without any fertility treatment. In 2012, five million children were born worldwide using in vitro fertilization and other assisted reproduction techniques.



From the Latin meaning “in glass,” the term “in vitro” is used because the first biological experiments involving tissue culture outside the living organism from which they originated were carried out in glass containers such as beakers, tubes of the test, or Petri dishes.

Nowadays, the scientific term “in vitro” refers to any biological procedure performed outside the organism. It would usually have occurred to distinguish it from an in vivo procedure, where the tissue remains within the living organism within the body. which is usually found

A colloquial term for babies conceived from in vitro fertilization, “test-tube babies,” refers to containers in glass or plastic resin tubes, called test tubes, which are commonly used in chemistry laboratories and biology.

However, in vitro fertilization is usually done in shallower containers called Petri dishes. A method of in vitro fertilization, autologous endometrial coculture, is done in organic material but is still considered in vitro fertilization.

Medical uses

In vitro fertilization can be used to overcome female infertility due to problems with the fallopian tubes, which makes it difficult to fertilize in vivo.

It can also help in male infertility, in those cases where there is a defect in sperm quality; In such situations, intracytoplasmic sperm injection (ICSI) can be used, where a sperm is injected directly into the ovule.

This is used when the sperm have difficulty penetrating the egg, and in these cases, the sperm of the partner or the donor can be used.

Intracytoplasmic sperm injection is also used when the number of sperm is deficient. When indicated, intracytoplasmic sperm injection increases the success rates of in vitro fertilization.

According to the guidelines of the National Institute of Excellence in Health and Care of the United Kingdom, in vitro fertilization treatment is appropriate in cases of unexplained infertility for women who have not conceived after two years of regular unprotected sex.

Success rates

Success rates of in vitro fertilization, the percentage of all in vitro fertilization procedures that result in a favorable outcome.

Depending on the type of calculation used, this result may represent the number of confirmed pregnancies, called the pregnancy rate, or the number of live births, reached the live birth rate.

The success rate depends on variable factors such as maternal age, the cause of infertility, embryonic status, reproductive history, and lifestyle factors.

Maternal age: younger candidates for in vitro fertilization are more likely to become pregnant. Women over 41 are more likely to get pregnant with a donated egg.

Reproductive history: Women who have been pregnant in many cases are more successful within Vitro fertilization treatments than those who have never been pregnant.

Due to advances in reproductive technology, the success rates of in vitro fertilization are substantially higher today than a few years ago.

Live birth rate

The live birth rate is the percentage of all in vitro fertilization cycles that lead to living birth. This rate does not include miscarriage or intrauterine fetal death, and multiple-order births, such as twins and triplets, are counted as a single pregnancy.

In 2006, Canadian clinics reported a 27% live birth rate. Birth rates in the youngest patients were slightly higher, with a success rate of 35.3% for those under 21 years of age, the youngest group evaluated.

The success rates for older patients were also lower and decreased with age, with 37 years of age with 27.4% and without live births for those more than 48 years, the oldest group evaluated.

Some clinics exceeded these rates, but it is impossible to determine if this is due to a superior technique or patient selection. It can artificially increase success rates by refusing to accept the most challenging patients or guiding them towards oocyte donation cycles (compiled separately).

In addition, pregnancy rates can be increased by placing several embryos with the risk of increasing the possibility of multiple.

Because not every in vitro fertilization cycle initiated will lead to oocyte retrieval or embryo transfer. Reports of live birth rates should specify the denominator: in vitro fertilization cycles started, fertilization recoveries in vitro, or embryo transfers.

The Society for Assisted Reproductive Technology (SART) summarized the 2008-9 success rates for US clinics for fresh embryo cycles that did not include donor eggs.

And they gave live birth rates for the age of the possible mother, with a maximum of 41.3% per cycle started and 47.3% for embryo transfer for patients under 35 years.

Attempts at in vitro fertilization in multiple cycles increase the accumulated rates of live births. Depending on the demographic group, one study reported 45% to 53% in three trials and 51% to 71% to 80% in six attempts.

Pregnancy rate

The pregnancy rate can be defined in several ways. In the United States, the pregnancy rate used by the Society for Assisted Reproductive Technology and the Centers for Disease Control (listed in the table in the Success Rates section) is based on the fetal heart movement observed in the examinations. Of ultrasound.

A French study estimated that 66% of patients who started in vitro fertilization treatment finally managed to have a child (40% during the in vitro fertilization treatment in the center and 26% after the interruption of the in vitro fertilization).

The achievement of having a child after interruption of in vitro fertilization was mainly due to adoption (46%) or spontaneous pregnancy (42%). In 2006, Canadian clinics reported an average pregnancy rate of 35%.

Predictors of success

The main potential factors that influence pregnancy rates (and live births) in in vitro fertilization have been suggested as maternal age, duration of infertility or subfertility, FSH, and several oocytes, all of which reflect the ovarian function.

The optimal age of the woman is from 23 to 39 years old at the time of treatment. Biomarkers that affect the chances of pregnancy from in vitro fertilization include:

Antral follicle count, with a higher count that provides higher success rates.

The levels of the anti-Müllerian hormone with higher levels indicate higher chances of pregnancy and live births after in vitro fertilization, even after adjusting for age.

Semen quality factors for the sperm provider. Level of DNA fragmentation measured, p. Eg using the Comet test, the mother’s advanced age, and the quality of the semen.

Women with ovarian-specific FMR1 genotypes, including het-norm / low, have significantly decreased the chances of pregnancy in vitro fertilization.

Elevation of progesterone (PE) on the day of final maturation induction is associated with lower pregnancy rates in in vitro fertilization cycles in women undergoing ovarian stimulation with GnRH analogs and gonadotropins.

Compared to a progesterone level below 0.8ng / ml, a level between 0.8 and 1.1ng / ml confers a pregnancy probability ratio of approximately 0.8. A status between 1, 2, and 3.0ng / ml confers a pregnancy probability ratio between 0.6 and 0.7.

On the other hand, progesterone elevation does not seem to confer a lower possibility of pregnancy in thawed cycles and cycles with the donation of ovules.

Characteristics of the cells of the cumulus oophorus and the granular membrane are easily aspirated during the recovery of the oocyte.

These cells are closely associated with the oocyte and share the same microenvironment. The expression rate of specific genes in these cells is associated with a higher or lower pregnancy rate.

An endometrial thickness (EMT) of less than 7 mm decreases the pregnancy rate by an odds ratio of approximately 0.4 compared to an endometrial thickness of more than 7 mm. However, such a low thickness is rarely produced, and any routine use of this parameter is considered unjustified.

Other determinants of the result of in vitro fertilization include:

Smoking reduces the likelihood that in vitro fertilization will produce a live birth by 34% and increases the risk of in vitro abortion during pregnancy by 30%.

A body mass index (BMI) greater than 27 causes a 33% decrease in the probability of having a live birth after the first in vitro fertilization cycle compared to those with a body mass index between 20 and 27.

In addition, pregnant women who are obese have higher rates of miscarriage, gestational diabetes, hypertension, thromboembolism, and problems during childbirth and increase the risk of congenital fetal anomalies. The ideal body mass index is 19-30.

Salpingectomy or laparoscopic tubal occlusion before in vitro fertilization treatment increases the chances for women with hydrosalpinges. Success with previous pregnancies and live births increases the possibilities.

Low alcohol/caffeine intake increases the success rate. The number of embryos transferred in the treatment cycle. Embryo quality

Some studies also suggest that autoimmune disease may also decrease the success rates of in vitro fertilization by interfering with the proper implantation of the embryo after transfer.

Aspirin is sometimes prescribed to women to increase the chances of conception through in vitro fertilization, but as of 2016, there was no evidence to prove it safe and effective.

A 2013 review and meta-analysis of randomized controlled trials of acupuncture as adjuvant therapy in vitro fertilization did not find a general benefit.

And he concluded that an apparent benefit was detected in a subset of published trials where the control group (those not using acupuncture) experienced a lower number than the average pregnancy rate due to the possibility of publication bias and other factors.

A Cochrane review concluded that the endometrial lesion performed in the month before ovarian induction seemed to increase the rate of live births and the clinical pregnancy rate in in vitro fertilization compared to no endometrial lesions.

There was no evidence of a difference between the groups in spontaneous abortions, multiple pregnancies, or bleeding rates. Evidence suggests that endometrial injury on the day of oocyte recovery was associated with a lower rate of live births or ongoing pregnancies.

For women, the intake of antioxidants (such as N-acetyl-cysteine, melatonin, vitamin A, vitamin C, vitamin E, folic acid, Myo-inositol, zinc, or selenium) has not been associated with a significant increase in the rate of live births or pregnancy rate in in vitro fertilization according to the Cochrane reviews.

The review found that oral antioxidants administered to men in couples with unexplained malefactors or subfertility can improve live birth rates, but more evidence is needed.

A Cochrane review in 2015 arrived at the result that there is no identified evidence regarding the effect of lifestyle advice before conception on the possibility of a live birth outcome.


Multiple births

The main complication of in vitro fertilization is the risk of multiple births. This is directly related to the practice of transferring multiple embryos in embryo transfer.

Multiple births are related to an increased risk of pregnancy loss, obstetric complications, prematurity, and neonatal morbidity with the potential for long-term damage.

Strict limits have been enacted on the number of embryos transferred in some countries (e.g., Great Britain, Belgium) to reduce the risk of high order multiples (triplets or more), but they are not universally followed or accepted.

Spontaneous division of embryos into the uterus after transfer may occur, but this is rare and could result in identical twins.

A double-blind, randomized study followed in vitro fertilization pregnancies that resulted in 73 infants (33 children and 40 girls) and reported that 8.7% of unmarried newborns and 54.2% of twins had a birth weight of <2,500 grams (5.5 lb).

Recent evidence also suggests that single offspring after in vitro fertilization have an increased risk of low birth weight for unknown reasons.

Distortions of the sexual relationship

It has been shown that certain types of in vitro fertilization, in particular, intracytoplasmic sperm injection (first applied in 1991) and blastocyst transfer (used for the first time in 1984), produce distortions in the sex ratio at birth.

Intracytoplasmic sperm injection leads to slightly more female births (51.3% of women), while blastocyst transfer leads to the delivery of significantly more children (56.1% of men).

Standard in vitro fertilization performed on the second or third day leads to an average sex ratio.

The epigenetic modifications caused by the prolonged culture that leads to the death of more female embryos have been theorized as the blastocyst transfer leads to a more significant proportion of males; however, adding retinoic acid to the culture may return this relationship to normality.

Propagation of infectious diseases

By washing sperm, the risk that chronic disease in the male that provides sperm to infect the female or offspring may reach negligible levels.

In men with hepatitis B, the Practice Committee of the American Society for Reproductive Medicine reports that sperm washing is not necessary for in vitro fertilization to prevent transmission unless the female partner has not been effectively vaccinated.

In women with hepatitis B, the risk of vertical transmission during in vitro fertilization is not different from the danger of spontaneous conception.

However, there is insufficient evidence to say that intracytoplasmic sperm injection procedures are safe in women with hepatitis B concerning vertical transmission to offspring.

About the possible spread of HIV / AIDS, the Japanese government banned the use of in vitro fertilization procedures for couples in which both partners are infected with HIV.

Although ethics committees previously allowed Tokyo’s Ogikubo Hospital in Tokyo to use in vitro fertilization for couples with HIV, Japan’s Ministry of Health, Labor and Welfare decided to block the practice.

Hideji Hanabusa, the vice president of Ogikubo Hospital, says that together with his colleagues, he managed to develop a method through which scientists can eliminate HIV from sperm.

Other risks for the egg supplier/retriever

The risk of ovarian stimulation is the development of ovarian hyperstimulation syndrome, mainly if human chorionic gonadotropin is used to induce the final maturation of oocytes. This produces swollen and painful ovaries.

It occurs in 30% of patients. Mild cases can be treated with over-the-counter medications, and issues can be resolved without pregnancy.

In moderate cases, the ovaries swell, and fluid accumulates in the abdominal cavities and may have symptoms of heartburn, gas, nausea, or loss of appetite. In severe cases, patients have a sudden excess of abdominal pain, nausea, and vomiting will result in hospitalization.

During egg retrieval, there is a slight chance of bleeding, infection, and damage to surrounding structures such as bowel and bladder ( transvaginal ultrasound aspiration ) as well as difficulty breathing, chest infection, allergic reactions to medications, or nerve damage ( laparoscopy) ).

Ectopic pregnancy can also occur if a fertilized egg develops outside the uterus, usually in the fallopian tubes, and requires immediate destruction of the fetus.

In vitro fertilization does not seem to be associated with an increased risk of cervical cancer, ovarian cancer, or endometrial cancer by neutralizing the confounding factor of infertility. Nor does it seem to impart an increased risk of breast cancer.

Regardless of pregnancy outcome, in vitro fertilization treatment is often stressful for patients.

Neuroticism and escapist coping strategies are associated with a greater degree of anguish, while the presence of social support has a relief effect.

A negative pregnancy test after in vitro fertilization is associated with an increased risk of depression in women but not an increased risk of developing anxiety disorders.

The results of pregnancy tests do not seem to be a risk factor for depression or anxiety among men.

Congenital disabilities

A review in 2013 came to the result that babies resulting from in vitro fertilization (with or without intracytoplasmic sperm injection) have a relative risk of congenital disabilities of 1.32 (95% confidence interval 1.24-1.42) compared with infants conceived naturally.

In 2008, an analysis of data from the National Study of Congenital Defects in the United States. UU found that specific congenital disabilities were significantly more common in babies conceived through in vitro fertilization.

Especially septal heart defects, cleft lip with or without cleft palate, esophageal atresia, and anorectal atresia; the mechanism of causality is not precise.

However, in a cohort study of 308,974 births (with 6,163 using assisted reproductive technology and children from birth through age 5), the researchers found:

“The increased risk of congenital disabilities associated with in vitro fertilization was no longer significant after adjustment for parental factors.”

Parental factors included known and independent risks of congenital disabilities such as maternal age, smoking, etc.

The multivariate correction did not eliminate the importance of the association between congenital disabilities and intracytoplasmic sperm injection (odds ratio corrected 1.57).

Although the authors speculate that the underlying factors of male infertility (which would be associated with intracytoplasmic sperm injection) may contribute to this observation and were not able to correct these confounding factors.

The authors also found that a history of infertility increased the risk in the absence of treatment (odds ratio 1.29), consistent with a Danish national registry study and “… implicates patient factors in this increased risk”.

The authors of the study of the Danish national registry speculate:

“Our results suggest that the reported higher prevalence of congenital malformations observed in newborn individuals after assisted reproductive technology is partly due to underlying infertility or its determinants.”

Other risks for the offspring

If the underlying infertility is related to abnormalities in spermatogenesis, it is plausible, but it is too early to examine that male offspring have an increased risk of sperm abnormalities.

In vitro fertilization does not seem to confer any risk concerning cognitive development, school performance, social functioning, and behavior.

In addition, it is known that babies with in vitro fertilization are as attached to their parents as those who were conceived naturally, and adolescents with in vitro fertilization are as well adjusted as those who have been conceived naturally.

Limited long-term follow-up data suggest that in vitro fertilization may be associated with a higher incidence of hypertension, impaired fasting glucose, increased total body fat composition, advancing bone age, subclinical thyroid disorder, depression, early clinical and excessive consumption of alcohol in offspring.

However, it is not known whether these possible associations are caused by the in vitro fertilization procedure itself, by the adverse obstetric results associated with in vitro fertilization, by the genetic origin of the children, or by still unknown causes related to the in vitro fertilization.

Increases in embryo manipulation during in vitro fertilization result in more deviated fetal growth curves, but the birth weight does not appear to be a reliable marker of fetal stress.

In vitro fertilization, including intracytoplasmic sperm injection, is associated with an increased risk of impression disorders (including Prader-Willi syndrome and Angelman syndrome), with an odds ratio of 3.7 (95% confidence: 1.4 to 9.7).

It is believed that an incidence of cerebral palsy related to in vitro fertilization and delayed neurological development is associated with the confounding factors of prematurity and low birth weight.

Similarly, it is believed that an incidence of autism and attention deficit disorder associated with in vitro fertilization is related to confounding factors of maternal and obstetric factors.

In general, in vitro fertilization does not cause an increased risk of childhood cancer. Studies have shown a decrease in certain cancers and a higher risk of others, including hepatoblastoma and retinoblastoma rhabdomyosarcoma.


Theoretically, in vitro fertilization could be done by collecting the contents of the fallopian tubes or the uterus of a woman after natural ovulation, mixing them with sperm, and reinserting the fertilized ovules into the uterus.

However, without additional techniques, the chances of pregnancy would be minimal.

Additional techniques routinely used in vitro fertilization include ovarian hyperstimulation to generate multiple ovules or transocenographic extraction of ultrasound-guided oocytes directly from the ovaries.

After which, the ovules and sperm are prepared, as well as the culture and selection of the resulting embryos before the embryo is transferred to the uterus.

Ovarian hyperstimulation

Ovarian hyperstimulation is the stimulation to induce the development of multiple follicles of the ovaries. It should begin with predicting response, for example, age, antral follicle count, and anti-Müllerian hormone level.

The resulting prediction of, p. The poor or hyper response to ovarian hyperstimulation determines the protocol and dose for ovarian hyperstimulation.

Ovarian hyperstimulation also includes the suppression of spontaneous ovulation. There are two main methods available: a gonadotropin-releasing hormone agonist protocol (usually longer) or a gonadotropin-releasing hormone antagonist protocol ( generally shorter).

In a standard gonadotropin-releasing hormone agonist protocol, the day the hyperstimulation treatment is initiated and the expected day of oocyte recovery can be chosen to fit the personal choice, while in a hormone-antagonist protocol gonadotropin-releasing should be adapted to the onset of previous menstruation.

On the other hand, the gonadotropin-releasing hormone antagonist protocol has a lower risk of ovarian hyperstimulation syndrome (OHSS), a life-threatening complication.

Injectable gonadotropins (usual analogs of follicle-stimulating hormone) for ovarian hyperstimulation itself are generally used under close surveillance.

Such control frequently verifies the estradiol level and, by gynecological ultrasonography, follicular growth. Generally, approximately ten days of injections will be necessary.

Natural in vitro fertilization

There are several methods called natural cycle In vitro fertilization:

  • In vitro fertilization does not use medications for ovarian hyperstimulation, while drugs for suppressing ovulation can still be used.
  • In vitro fertilization uses ovarian hyperstimulation, including gonadotropins, but with a gonadotropin-releasing hormone antagonist protocol so that the cycle starts from natural mechanisms.
  • Transfer of frozen embryos; In vitro fertilization using ovarian hyperstimulation, embryo cryopreservation, and embryo transfer in a subsequent natural cycle.

In vitro fertilization without drugs for ovarian hyperstimulation was the method for the conception of Louise Brown.

This method can be used successfully when women want to avoid taking ovarian stimulant medications with their associated side effects.

The Human Fertilization and Embryology Authority has estimated that the live birth rate is approximately 1.3% per in vitro fertilization cycle without hyperstimulation drugs for women aged 40-42.

In vitro fertilization is a method in which a small dose of ovarian stimulant medication is used for a short period during a woman’s natural cycle to produce 2 to 7 ovules and create healthy embryos.

This method seems to advance in the field to reduce complications and side effects for women and is aimed at quality and not at the number of ovules and embryos.

A study comparing a gentle treatment (mild ovarian stimulation with gonadotropin-releasing hormone antagonist co-treatment combined with the transfer of a single embryo).

A standard treatment (stimulation with a long-acting hormone agonist and the transfer of two gonadotropin-releasing embryos) reached the result that the proportions of accumulated pregnancies that resulted in live full-term births after one year were 43.4% with treatment slight and 44.7% with standard therapy.

In vitro, soft fertilization may be cheaper than conventional in vitro fertilization and with a significantly reduced risk of multiple ovarian hyperstimulation syndrome and gestation.

Final induction of maturation

When the ovarian follicles have reached a certain degree of development, the induction of the final maturation of the oocytes is carried out, generally using an injection of human chorionic gonadotropin. Commonly, this is known as the “trigger pull.”

Human chorionic gonadotropin acts as an analog of luteinizing hormone, and ovulation occurs between 38 and 40 hours after a single human chorionic gonadotropin injection.

But egg retrieval is done at a time generally between 34 and 36 hours after the injection of human chorionic gonadotropin, which is just before the follicles break.

This serves to program the egg retrieval procedure at a time when the eggs are fully mature. Injection of human chorionic gonadotropin confers a risk of ovarian hyperstimulation syndrome.

Using a gonadotropin-releasing hormone agonist in place of human chorionic gonadotropin eliminates most of the risk of ovarian hyperstimulation syndrome, but with a reduced delivery rate if the embryos are transferred fresh.

For this reason, many centers will freeze all oocytes or embryos after the agonist trigger.

Egg recovery

The ovules are recovered from the patient by a transvaginal oocyte retrieval technique, which involves an ultrasound-guided needle that pierces the vaginal wall to reach the ovaries.

Through this needle, the follicles can be aspirated, and the follicular fluid is passed to an embryologist to identify the ovules. It is common to eliminate between ten and thirty eggs.

The recovery procedure usually takes between 20 and 40 minutes, depending on the number of mature follicles, and is generally done under conscious sedation or general anesthesia.

Preparation of egg and sperm

The identified eggs are stripped of the surrounding cells in the laboratory and prepared for fertilization.

Oocytes can be selected before fertilization to choose the eggs with optimal chances of a successful pregnancy.

Meanwhile, the semen prepares for fertilization by removing the dormant cells and seminal fluid in sperm washing.

If the semen is supplied by a sperm donor, it will generally have been prepared for treatment before being frozen and quarantined and will be thawed, ready for use.


Sperm and egg are incubated together at approximately 75,000: 1 in a culture medium for actual fertilization to occur.

A review in 2013 came to the result that the duration of this co-incubation of approximately 1 to 4 hours results in pregnancy rates significantly higher than those of 16 to 24 hours. In most cases, the egg will be fertilized during co-incubation and show two pronuclei.

In certain situations, such as low sperm count or motility, a single sperm can be injected directly into the egg by intracytoplasmic sperm injection.

The fertilized egg is passed to a particular growth medium and left for about 48 hours until the egg is composed of six to eight cells.

In the intrafallopian transfer of gametes, the ovules are extracted from the woman and placed in one of the fallopian tubes, together with the man’s sperm.

This allows fertilization to take place inside the woman’s body. Therefore, this variation is fertilization in vivo, not in vitro.

Embryo culture

The main duration of embryo culture is up to the cleavage stage (two or four days after co-incubation) or the blastocyst stage (five or six days after co-incubation).

The embryo culture until the blastocyst stage confers a significant increase in the rate of live births by embryo transfer.

But it also confers a small number of embryos available for embryo transfer and cryopreservation, so the cumulative rates of clinical pregnancy increase with the transfer of the excision stage.

The second day of transfer instead of day three after fertilization has no difference in the live birth rate.

There are significantly higher odds of premature birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) between births with embryos cultured up to the blastocyst stage than in the excision stage.

Embryo selection

Laboratories have developed classification methods to judge the quality of embryos and oocytes. There is significant evidence that a morphological scoring system is the best strategy for embryo selection to optimize pregnancy rates.

Since 2009, when the first time-lapse microscopy system for in vitro fertilization for clinical use was approved, morphogenetic scoring systems have improved pregnancy rates further.

However, comparing all the different types of embryonic imaging devices with time-lapse, with or without morphogenetic scoring systems, against conventional embryonic evaluation for in vitro fertilization.

There is not enough evidence of a difference in a live birth, pregnancy, fetal death, or miscarriage to choose between them.

Embryo transfer

The number that will be transferred depends on the available number, the woman’s age, and other health and diagnostic factors. In countries such as Canada, the United Kingdom, Australia, and New Zealand, a maximum of two embryos are transferred, except in unusual circumstances.

In the United Kingdom, and according to the regulations of the Human Fertilization and Embryology Authority, a woman older than 40 years can have up to three embryos transferred while in the USA. UU

Although medical associations have provided practice guidelines, there is no legal limit on the number of embryos that can be transferred.

Most clinics and regulatory bodies in countries try to minimize the risk of multiple pregnancies since it is not uncommon for various embryos to be implanted if numerous sources are transferred.

The embryos are transferred to the patient’s uterus through a thin plastic catheter that passes through the vagina and cervix. Several sources can be given to the uterus to improve the chances of implantation and pregnancy.

Associated medication

Luteal support is the administration of medications, usually progesterone, progestins, human chorionic gonadotropin, or gonadotropin-releasing hormone agonists, and often accompanied by estradiol.

To increase the success rate of implantation and early embryogenesis, complementing and supporting the function of the corpus luteum.

A Cochrane review found that human chorionic gonadotropin or progesterone administered during the luteal phase may be associated with higher live births or ongoing pregnancies, but the evidence is inconclusive.

Co-treatment with gonadotropin-releasing hormone agonists improves outcomes through a live birth rate. Absolute risk reduction of + 16% (95% confidence interval +10 to + 22%).

On the other hand, growth hormone or aspirin as an adjuvant medication in in vitro fertilization has no evidence of a public benefit.