Improving the safety of the embryo and the patient during in vitro fertilization procedures.

The problem of the lack of offspring is becoming an increasingly serious challenge for medicine, because nearly every fifth couple at reproductive age has problems with conception. Evidence suggests that the scale of this phenomenon will still increase [ 1 ]. Fertility and the health state of the baby depends on genetic, environmental, social factors and healthcare both [ 2 ]. For many couples the only chance for possessing offspring will be the procedure of in vitro fertilization (IVF). In vitro fertilization procedures are the most effective method of infertility treatment, and its chance for success depends on many factors [ 3 ]. The procedure of this method of treatment is multi-stage and requires the engagement of specialists in various domains. The provision of safety to the embryo is directly translated into its quality and, consequently, the probability of achieving pregnancy and, to a great extent, depends on the cooperation between the physician and the embryologist [ 4 ]. At present, the minimization of invasiveness of the procedure of IVF is the main factor which can contribute to the achievement of pregnancy and delivering a healthy baby after this procedure. The procedure of IVF consists of several stages: stimulation of ovulation, retrieval of oocytes (puncture), fertilization of the ova, culture of embryos, and subsequently, the transfer of embryos to the uterine cavity. Unused oocytes or embryos are frozen in order to use them in the future. The principles of managing IVF in Poland are regulated by the Act of 25 June 2015 in the matter of infertility treatment [ 5 ]. The most important indications for performing the IVF procedure are: bilateral obstruction of fallopian tubes, considerable deterioration of the quality of sperm parameters, advanced endometriosis, as well as the situation when other treatment methods have failed, such as intrauterine insemination [ 4 , 6 , 7 ]. The IVF procedure is also recommended to women who are at risk of exhaustion of the ovarian reserve. In vitro fertilization procedures may also secure the fertility of patients after radiotherapy and chemotherapy.

Insertion of the embryo into the uterine cavity consists in the introduction of the embryo placed in a special catheter into the uterine cavity and injecting it into the endometrium. This procedure is traumatizing for both the embryo and uterine tissues. In order to reduce the invasiveness of this procedure, the physician should comprehensively assess the individual anatomical conditions occurring in individual patients. This consists in ultrasound assessment of the angle between the endometrium line and the canal of the cervix, and obtaining information concerning possible difficulties while introducing the catheter which had occurred during previously performed insemination procedures or IVF. This is to minimize damage which may be caused by the catheter introduced into the uterine cavity, such as the occurrence of bleeding into the uterine cavity or, in extreme cases, perforation of the uterus muscle. Both strong anteflexion and retroversion of the uterus may contribute to the technical difficulties during the transfer of the embryo. This type of structure of the uterus may favor the situation when the introduced catheter will scratch the internal orifice of the uterus and endometrium. In cases of anteflexion of the uterus, this problem may be avoided by the strong filling of the urinary bladder with urine which, by exerting pressure on the uterus, will increase the angle between the endometrium line and the canal of the cervix. As the last resort, during difficulties with the introduction of the catheter, the cervix may be pulled with forceps. Ruggedness and stenoses occurring in the cervix, which hinder free introduction of the catheter, may also cause great difficulties during its introduction. In such a situation, the transfer must be preceded by the procedure of dilatation of the uterus (Hegar dilator), and the interval between these two activities should be as long as possible. According to the degree of difficulty of transfer, there is a possibility to select the most appropriate type of catheter for the performance of this procedure. The differences between catheters consist in their stiffness, possibilities for stiffening, diameters and visibility during ultrasound. The decision concerning the selection of a catheter is individual. It is important that the IVF laboratory has at its disposal a wide choice of these instruments. Ruhlmann’s results suggest that a softer catheter may help with difficult embryo transfers. Softer catheters, as also reported by other authors, resulted in better implantation rates [ 22 ]. The lack of invasiveness of embryo transfer is possible due to the preview of catheter insertion into the uterine cavity by ultrasound. The visibility of the catheter allows the positioning of the embryo in an optimum place, and also allows avoidance of perforation of the wall of the uterus. Visualization of the catheter depends of the type of the catheter and individual structure of a patient. The introduction of the catheter may be controlled trans-abdominally with a full urinary bladder; however, in obese patients or those with strong retroversion of the uterus, this method is of limited usefulness. If the trans-abdominal assessment is ineffective, the catheter may be traced using a transvaginal probe (tv). The site of insertion of the embryo may be selected without insertion of the catheter under ultrasound guidance, but performing previous uterine length measurement (ULMb-ET). Revelli et al. , in a prospective, randomized, non-inferiority trial, compared the embryo transfer technique based on previous uterine length measurement with transabdominal ultrasound-guided embryo transfer (UGET) in a large population of patients submitted to IVF. The researchers confirmed that ULMb-ET technique leads to IVF results comparable to those obtained with UGET, but is better tolerated than UGET and is technically easier to perform for a single operator [ 23 ]. Kwon et al. undertook an attempt to evaluate at what distance from the fundus of the uterus (1 or 2 cm) it is best to place the embryo, and did not find any differences in the number of achieved pregnancies according to the placement of the embryo [ 24 ]. The use of the two-piece catheter in case of possible difficulties with the introduction of the catheter into the uterine cavity shortens the time of the embryo staying outside the incubator. In addition, the first catheter inserted without the embryo is placed relatively shallowly in order not to irritate the walls of the uterus, while the second catheter – thinner and softer – which is introduced into its lumen has less possibilities to damage the tissues of the uterus. In order to minimize the damage to the embryo during its transfer, it is very important to maintain a relatively low pressure while introducing it into the uterine cavity. Experiments by Grygoruk et al. on animal models showed that fast ejection of the transferred load can trigger both morphologic changes and apoptosis in mouse blastocysts. A reduction of the ejection speed of the transferred load minimizes injury to the embryos [ 25 , 26 ]. Recently, a report was published concerning the effectiveness of using a pump-regulated embryo transfer (PRET) device to minimize the pressure during transfer. Caanen et al. confirmed that the PRET device generates significantly smaller variance of the positioning of the embryo(s) into the uterine cavity. This resulted in an ongoing pregnancy rate of 21% in the PRET vs. 17% in the manual ( p = 0.22) transfer group; frozen-thawed embryo transfers resulted in 17.5 vs. 10.9% ( p = 0.097), respectively [ 27 ]. It seems that the availability of this device in Poland may contribute to the reduction in invasiveness of embryo transfer. The final stage involves checking whether the embryo became stuck in the catheter after the procedure. If it happens, this allows its re-introduction into the uterine cavity; however, in such cases, our experience suggests an unfavorable prognosis. The cause of the occurrence of this phenomenon is unknown. An analysis performed by Craciunas and Tsampras concerning the recommendations for patients after transfer concerning bed rest showed that bed rest following ET did not improve clinical pregnancy and live birth rates, but reduced the implantation rate [ 28 ].

Ovarian puncture is the procedure of collecting the oocyte from the follicles in the ovary, which is performed 35–36 h after the induction of ovulation induced by the administration of human chorionic gonadotropin (hCG). This procedure is performed using a needle introduced through the vaginal fornix into the ovary under the control of a transvaginal ultrasound probe. The aspirated follicular fluid is taken to the laboratory, where the oocytes are isolated. The procedure is most often performed under short-term intravenous anaesthesia. The invasiveness of this procedure depends on the anatomical location of the ovary, the risk of introduction of infection, and the possibility of inducing an internal and external hemorrhage, as well as the experience of the person performing the puncture [ 12 ]. The thickness of the puncture needle is of great importance for the safety of the procedure. A smaller diameter of the needle, in case of tearing of the blood vessel, decreases the risk of occurrence of hemorrhage and reduces the trauma of tissue which is punctured in order to reach the ovary. At the same time, fine needles are less stiff, which in the case of puncture of an ovary with a thickened shell located at a considerable distance from the ultrasound probe may cause technical difficulties with puncturing the ovary wall. In such a situation, the needle may easily bend and slip from the ovary, traumatizing adjacent tissues. The thickness of the needle and speed of aspiration of the follicular fluid also affect the pressure within the needle, which may exert an effect on the quality of the oocyte, and consequently the embryo. This problems was analyzed by Rose, who published human and animal studies, which together with topics from mathematics and mechanics were used to try to understand the importance of different choices that could be made in structuring a transvaginal oocyte retrieval procedure in humans. The published literature suggests that the highest oocyte recovery rate occurs using higher pressures and thicker needles, but this comes at the cost of damaging the cumulus oocyte complex. It is likely that this damage is caused by the sheer stress forces exerted on the cumulus oocyte complex, due to parabolic forces associated with laminar flow within the needle, and is likely worsened by irregular forces during intervals of turbulent flow occurring with entry into the needle. Larger needles also cause more pain and may be associated with more blood loss. Higher velocity entry into the follicle, needle rotation to prevent premature blockage of the lumen, and carefully timed applications of aspiration pressure theoretically optimize the oocyte retrieval technique [ 13 ]. The location of the ovaries in the smaller pelvis varies individually, and also depends on the past inflammatory states or procedures which, by generating adhesions, may contribute to the hindered access to them with the puncture needle. Such a situation increases the invasiveness of the procedure of oocyte retrieval, and sometimes requires puncturing the urinary bladder or the uterus. Reduction of the number of insertions of the needle contributes to minimization of the occurrence of hemorrhage or introduction of infection. It is the more difficult the larger the ovary, with which we are confronted, among other situations, during the OHSS [ 14 ].

Invasiveness of the IVF procedure for the woman and the embryo varies on an individual basis. Minimization of the invasiveness of IVF requires experience of the staff performing the procedure, especially with respect to the assessment of risk for an individual patient. Technologies related to IVF are constantly being improved, and the effectiveness of the selected individual treatment methods is not always scientifically confirmed.

In order to obtain good quality egg cells during IVF, stimulation of ovulation is performed using gonadotropins in combination with the co-administration of a gonadotropin-releasing hormone-antagonist (GnRH) or GnRH agonist. Selection of the proper dose of gonadotropins, on the one hand, is the precondition for obtaining a proper number and good quality ova, and on the other hand, allows one to avoid the risk of occurrence of the ovarian hyperstimulation syndrome (OHSS), which creates a life threat for patients subjected to IVF [ 8 ]. The ovarian hyperstimulation syndrome is the complication of stimulation of ovulation taking place with the enlargement of the ovaries. The basic feature of the ovarian hyperstimulation syndrome is increased permeability of capillaries, resulting in the movement of fluid from the vascular space to the third space. The consequence of this may be embolism, renal, hepatic and respiratory failure. Mortality in OHSS is caused by electrolyte disorders, multi-organ failure, and thrombosis of the cerebral vessels. According to the latest European Society of Human Reproduction and Embryology report, the incidence of OHSS ranges from 0.18% to 1.40% in European countries [ 9 ]. The risk factors of this syndrome include age under 35, polycystic ovary syndrome (PCOS) with a high level of anti-Müllerian hormone (AMH), asthenic silhouette, concentration of estradiol over 3,000 pg/ml, the number of ovarian follicles exceeding 20, and application of GnRH protocols. The occurrence of this syndrome exerts a very negative effect on the quality of the embryos obtained [ 10 ]. The opinion in the matter of OHSS was specified by a group of experts in 2015. The group considered that there is a need for standardization of the definition and classification of the clinical syndrome of OHSS to allow further conclusive research. Interventions with evidence of effect in reducing OHSS include the use of metformin in women with PCOS, use of a GnRH antagonist rather than a GnRH agonist, and use of GnRH agonist triggers in GnRH antagonist stimulation cycles. The consensus view was that reducing the dose of follicle-stimulating hormone (FSH), freezing all embryos and transferring a single embryo were appropriate interventions to reduce OHSS. Agreement could not be reached on coasting, the lowest number of oocytes to consider freezing all embryos and management after cancellation of oocyte retrieval [ 11 ]. Knowledge of the risk factors of OHSS is the basic method to avoid its occurrence. Early threats resulting from the course of OHSS concern primarily the period of 3–7 days after puncture and depend on the results of stimulation, whereas late risks occur 12–17 days after the procedure and depend on pregnancy. Puncture performed in these patients, due to the considerable enlargement of the ovary, is a more invasive procedure than in the case of an ovary of a normal size.