Since the introduction of ICSI back 28 years till now ICSI is widely used to treat malefactor as well as female factor infertility. However, studies had shown concern of the pregnancy outcome in ICSI over conventional IVF in couples with non-male factor infertility. Studies had shown an+ altered pregnancy outcome in ICSI compared with natural conception. So far no difference in neurodevelopment in ICSI and spontaneously conceived (SC) children has been found. Additionally, epigenetic disorders and imprinting disorders have also been found in ICSI born children in some studies but opposing studies have also been found in literature.
Even though studies had found various outcome data in ICSI conceived children, there are limitations in the study conducted so far. Further studies in future which look into the more developmental aspect as well as long term studies are required for the better understanding of ICSI outcome.
Over the past 40 years assisted reproductive technologies (ART) have been acting as a treatment for infertility together with conventional IVF (In vitro Fertilization) and ICSI (Intracytoplasmic sperm injection) (Crawford & Ledger, 2018). These highly complex technologies are used in increasing frequencies all over the world and over five million babies are conceived worldwide in this manner (Adamson et al., 2013). In conventional IVF, the oocyte and several thousand spermatozoa are placed together in a petri dish in the laboratory in which the spermatozoa are left to spontaneously find and fertilize the oocyte where as in case of ICSI a single sperm is injected directly into an oocyte to assist fertilization.
Since the birth of the first babies using ICSI in 1992, ICSI has become quintessential to modern ART (Carmelidi, 2016). Worldwide, most clinics perform ICSI for moderate-to-severe male factor infertility. ICSI is the preferred method of fertilizing oocytes in men with ejaculatory dysfunction, retrograde ejaculation or paraplegia-associated complications (Trofimenko et al., 2016). ICSI is also indicated in couples with a history of poor fertilization or complete fertilization with conventional IVF. Many clinics utilize ICSI for non-male factor indications, often at their own discretion. Some of these indications include unexplained infertility, low oocyte yield, advanced age and cryopreservation of embryos for fertility preservation (Zheng et al., 2019)
Concerns have been raised regarding the safety of the procedure since its introduction. The primary concern in the invasive nature of the procedure and the fact that it bypasses the natural selection process and use of sperm that would not be able to fertilize the oocyte without ART intervention (Alukal et al., 2008). The latest world report on fertility treatment suggests that in many countries ICSI has become the standard infertility treatment even in couples who would also get pregnant with IVF. The percentage of ART procedures is significantly increasing all over the world. With this increased usage, the need to understand any potential adverse effects on ICSI-conceived offspring is imperative (Alukal & Lamp., 2008).
Compared to other therapeutic procedures used in medicine, ART had never undergone rigorous safety testing before its clinical trials (Friedler et al., 2012). Since infertility treatment overcome the natural barrier that prevent fertilization and in many cases infertility phenotype may have a genetic basis, the possibilities of unwanted genetic traits getting transmitted to offspring can’t be neglected (Alukal et al.,2008). In case of untreated couple their infertility represents the lethality within the gene pool, as it blocks the transmission of undesired genes to any offspring (Cariati et al., 2019). When it comes to ART treatment large number of couples undergo fertility treatment without a proper knowledge regarding the base of their infertility as well as the potential long term risk for their offspring (Zagami et al.,2019).
Despite the standardization of ICSI over the past 25 years, concerns about the technique have arisen (Pereira et al., 2017). The concern regarding ICSI arises from the perception that the spermatozoon for injection is selected arbitrarily and also important steps of fertilization like sperm-zona binding and oolemma fusion are completely bypassed (Neri et al., 2014). Moreover, there is still concern about the transmission of undesirable genetic traits from suboptimal spermatozoa which leads to genomic or phenotypic abnormalities in the progeny (Alukal et al., 2008). So far may studies have done to analyze the long-term clinical data associated with the pregnancy, perinatal, developmental and health outcomes of ICSI children.
ICSI & pregnancy outcome
Even though pregnancies after ART mostly result in normal healthy outcomes, there is an increased concern for the obstetric and neonatal complications compared to naturally conceived pregnancies (Zhu et al., 2016). So far various studies have looked into the pregnancy outcome of IVF/ICSI, the results are often inconclusive (Datta et al., 2015). A study conducted by Nouri et al., comparing IVF versus ICSI-conceived pregnancies during the period of 2003-2009 found that course of pregnancy to be more complicated after IVF, whereas the primary fetal outcome seemed to be better in this group than after ICSI treatment (Nouri et al., 2013). Since ICSI is widely used nowadays regardless of the type of infertility, impact of ICSI on non-male factor infertility is a concern. Studies have shown that fertilization rate, clinical pregnancy rate, live birth rate were significantly higher in the IVF group compared with ICSI in normospermic men (Sustar et al., 2019).
In case of azoospermia which contribute to 10% of male infertility, implication of ICSI allowed the possibility to father their own progeny (Halliday et al., 2012). An earlier study conducted by Wang et al., in 2002 could find that risk of gestational hypertension was doubled in women treated with ICSI by surgically obtained sperm and the risk of pre-eclampsia was tripled compared to the control group (Wang et al., 2002). One of the latest study published in 2020 in China over a period of 10 years could find that the clinical pregnancy rate as well as implantation rate of surgically retrieved sperm group were significantly higher than ejaculated sperm group. Most of the clinical pregnancy outcomes were comparable between surgically retrieved sperm group and ejaculated sperm group the miscarriage rate per transfer, ectopic pregnancy rate per clinical pregnancy, induced abortion rate per clinical pregnancy and fetal deaths per clinical pregnancy. Interestingly they could find that the live delivery rate per transfer of surgically retrieved sperm group was significantly higher than that of ejaculated sperm group (Jin et al., 2020).
In case of different types of azoospermia, pregnancy outcome studies had shown a strong tendency towards lower gestational age among the singletons and a higher percentage of premature twins in the non-obstructive azoospermia group, when comparing two different subgroups of azoospermic patients (Esteves et al., 2013).
ICSI & postnatal outcomes
Earlier studies of ICSI outcomes has demonstrated a higher rate of preterm birth and low birth weight, there are limitation in considering these data because these outcomes were mainly mediated by multifetal gestation due to multiple embryo transfer. In literature long-term outcome of ICSI is studied under 4 major categories which include, perinatal outcome and congenital malformation, developmental outcomes, medical health and reproductive health (Pereira et al., 2017).
Various studies have looked into major and minor congenital malformations; the studies cannot be compared due to limitations in the sample. ASRM had reported previously that the risk of having congenital malformation is 4.2% in IVF/ICSI cycles. Even though previous studies did not shown much differences between IVF and ICSI, study by Davies et al. showed a clear association of increased birth defect in ICSI even after multivariate adjustment (Wong et al., 2013)
Moreover, there is a limited data available on ICSI fetal karyotypes reveal that when compared with general neonatal population, there is a slight increase in chromosomal anomalies especially in sex chromosomes (Bonduelle et al., 2002).
A review conducted by Esteves et al., in 2018 about the consequence of ICSI for male infertility to the offspring. The study had shown that there is an increased risk of chromosomal abnormalities, particularly affecting the sex chromosomes in children conceived through ICSI when compared with naturally conceived children. Also they had pointed out the uncertainty about the increased risk of cancer in children conceived using ICSI even though some evidence indicates that certain cancer types are more common in children conceived using ICSI than in naturally conceived children (Esteves et al., 2018). Further studies are required for a clear understanding about these associations.
Earlier studies before 2000 had raised the concern of neurodevelopment of ICSI conceived children as many of the previous studies had shown data supporting the statement showing lower score of Bayley mental development index (MDI) and developmental delay ICSI born compared to the spontaneously conceived babies (Papaligoura et al., 2004). A systematic review of long-term follow-up of ICSI conceived offspring compared with spontaneously conceived offspring post neonatal period was published in 2018 and had shown that most studies of good quality suggest strongly that there is no difference in neurodevelopment in ICSI and spontaneously conceived (SC) children as indicated by similar cognitive and motor performance, and in some studies behavior and family relations (Catford et al., 2018). Although few studies had shown significant differences between the groups the majority of which present clinically insignificant findings or have important methodological limitations (Bowen et al., 1998; Ponjaert-Kristoffersen et al., 2004, 2005; Sanchez-Albisua et al., 2007; Knoester et al., 2008a).
When reviews looked into the general health of ICSI conceived offspring, fair quality data suggested that they are at an increased risk of urogenital surgeries, undescended testis, surgical interventions, hospital admissions compared to SC children (Catford et al., 2018). Although the studies are limited to childhood assessment, future studies on young adults will be helpful to overcome the confusion and give a better picture of the situation.
So far three studies published between 2006 and 2010 had looked into the vision and hearing of ICSI born at 5 years of age, and they had shown that these characteristics are comparable between ICSI and SC children. Evidence of abnormal retinal vascularization was found in some reports which leads to the conclusion that ICSI-conceived offspring may be at increased risk of cardiovascular disease.
One of the contributing factor for male infertility is thought to be genetic etiology (Karanfilska et al., 2012). In such cases there is a high risk of transmission of these causes to offspring. Congenital bilateral absence of the vas deferens (CBAVD), Y chromosome microdeletions are transmitted to male offspring by ICSI in such manner (Alukal et al., 2008). Studies so far conducted on pubertal ICSI-conceived offspring are reassuring, but they have the limitation of incomplete data. Recent studies had shown impaired spermatogenesis in ICSI-conceived young adult male compared to the control. Belva et al., in 2016 looked into the semen quality of young adult ICSI offspring, the study was carried out on 54 young adult ICSI men of the age 18-21, in result they could find that young ICSI adults had a lower median sperm concentration, total sperm count and total motile sperm count in comparison to spontaneously conceived (Belva et al., 2016). But the study has its own limitation due to the small sample size. Due to the time barrier the fertility of ICSI conceived males also the extent of their transgenerational inheritance of infertility is still unknown. Further studies in the future will be needed for better understanding of the remaining concerns.
ICSI has been widely opened the door of parenthood for patients with azoospermia even in case severe testicular failure. Due to the existing concern of increased chromosomal aneuploidy, follow up studies are extremely important. A systematic review by Esteves et al. shown either a decrease or no difference in pregnancy outcomes with ICSI in cases of nonobstructive azoospermia and obstructive azoospermia. In an overall there was no significant differences were found in short-term neonatal outcomes and congenital malformation rates between children from fathers with nonobstructive azoospermia and obstructive azoospermia. A study by Jin et al., in 2020 showed that there is no difference in the incidence of congenital malformations between epididymal sperm, testicular sperm and ejaculated sperm groups (Jin et al., 2020.)
ICSI &epigenetic disorders
Since ART procedures are involved with handling of germ cells and preimplantation embryo in vitro at critical stage of development during which genome-wide epigenetics reprogramming occur (Kohda et al., 2013). Concern has raised that such epigenetic changes may be transmitted to offspring leading to a high risk of imprinting and other disorders. Studies published previously had suggested that ART have increased the incidence of Beckwith-Wiedemann syndrome (BWS), Angelman syndrome (AS), Prader-Willi syndrome (PWS), and Silver-Russell syndrome (SRS) (Hattori et al., 2019)
A study by Cox et al., reported on two unrelated children having Angelman syndrome, both of whom were conceived by ICSI. Molecular investigation of the cases found that they were caused by sporadic imprinting defect. There is a strong possibility of rare coincidence exist in this two cases, but authors pointed out the possibility of artificial fertilization by ICSI interfering with establishment of the normal methylation pattern in the oocyte (Cox et al., 2002).
But there are contradicting studies Santos et al. showed following research on 76 ICSI embryos that insemination procedure does not cause an increase in incidence of epigenetic error. The study has also shown that DNA methylation pattern was consistent up to blastocyst stage when compared with those obtained from conventional insemination (Santos et al., 2010). Ghosh et al. compared methylation status of CCGG sites in the placentas between ICSI and IVF and no significant differences were obtained (Ghosh et al., 2017). Further studies are most certainly needed, and given that these defects are usually quite rare, long-term follow-up of large cohorts from multiple centers will be needed get conclusive result.
CHALLENGES AND FUTURE ASPECTS
So far in the literature, many studies had looked into the various outcome of ICSI including pregnancy outcome, perinatal development, postnatal development etc. There are certain challenges associated with comparing the outcomes of ICSI from various studies and coming to a conclusive data. It includes lack of standardized reports of various parameters used for ICSI outcome studies especially congenital abnormalities, lack of standardization of ovarian stimulation during oocyte pick up, lack of comparable study groups, inability to design and execute prospective, blinded, and well-controlled trials due to obvious ethical constraints.
Another concern while studying risk associated with ICSI as it is difficult to understand the reason behind risk, whether it is technique related or related to genetic defects of the parents. Since the oldest child conceived by ICSI is about 28 years old now, there are only limited long term studies of ICSI offspring are available. There are certain limitations in the follow up studies also, since few couple seek treatment at clinics far from their home and once pregnancy is achieved follow up treatment are continued by community physicians, such couples are often lost during follow-up studies. Due to the mobile nature of society, patients are lost from follow up for other reasons also.
There are additional challenges faced by ICSI/IVF follow up studies. Often assessment of IVF/ICSI offspring are often carried out by pediatricians as part of a routine neonatal health exam, yet a genetic division may have a different criterion for a disorder. Also there is a possibility of the ICSI conceived children undergoing more close examination than the naturally conceived children- the closer you look there is a greater likelihood of finding an abnormality.
Future studies with long term follow up and more detailed data will be helpful to attain a conclusive idea regarding the outcomes of ICSI.
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- Pereira, N., O’Neill, C., Lu, V., Rosenwaks, Z., & Palermo, G. D. (2017). The safety of intracytoplasmic sperm injection and long-term outcomes. Reproduction, 154(6), F61-F70.