**5. Conclusion**

*Embryology - Theory and Practice*

 **4.3 Embryogenesis and hCG, influence of contaminants**

inner cell mass, or trophectoderm characteristics.

Often, hCG is also known as "the hormone of pregnancy". It plays an important part for establishing and maintaining pregnancy, and it is extensively used in IVF procedures. A serial measurement of hCG every 48 hours is being used to confirm the early pregnancy and to distinguish between normally progressing pregnancies from ectopic pregnancies or spontaneous abortions [10]. It was shown that the miscarriage rate is higher when assisted reproductive techniques (ARTs) are applied than with naturally occurring pregnancy [11]. Girard et al. evaluated the association between early β-hCG concentration increases, blastocyst morphology, and pregnancy evolution in a single-blastocyst transfer program. In most IVF laboratories, blastocyst transfers are associated with higher success rates of implantation as compared with the cleavage stage embryo as shown by Oron et al. [12] and Girard et al. [10]. Most laboratories report that blastocysts are selected for transfer according to their morphological characteristics. That means that physicians decide on implantation based on, that is, expansion degree, hatching status of the blastocysts,

It is taught that hCG is involved in embryo implantation by modulating the activity of collagenases and plasminogen activators in an in-vitro system, as described by Yagel et al. [13]. Furthermore, it is an interesting and noteworthy feature that most of the mediators that have earlier been considered essential for the implantation process (i.e., EGF and IL-1/IL-6) are also involved in the regulation of hCG biosynthesis by the placental syncytiotrophoblasts [13–15] probably by modulating trophoblast differentiation. Therefore, Licht et al. postulated that hCG may play a central part in the hypothetical embryo-maternal cross talk and tested the hypothesis by simulating the effect of a very early pregnancy on the decidualized endometrium. The results suggested that, no immunoreactive hCG was found in the peripheral circulation (hCG<5 mIU/mL) and the treatment did not alter progesterone secretion by the

As described in previous paragraph, urinary-derived hCG contains high number of contaminant proteins. Considering that, particularly, EGF is present in high concentrations in almost all tested commercial preparations of urinary-derived hCG, and additional experiments are needed to find out whether the effects observed are

Furthermore, contaminant proteins identified in hCG formulations can be the source of severe allergic reactions and can also trigger immune response that must not necessarily been manifested externally; however, it can negatively affect embryo implantation and embryogenesis. Koh et al. [16] and Phipps et.al [17] described the cases of IgE-mediated immunoreaction after intramuscular administration of urinary-derived gonadotropins. This type of allergic reactions occurs shortly after administration of urinary-derived gonadotropin, and it occurs with symptoms like shortness of breath, wheezing, flushing, general weakness, and dizziness. In all reported cases, the IgE-mediated allergic reaction could be confirmed after intradermal skin testing with the same uhCG lot. Testing with rhCG triggered no reaction, thus confirming the theory that some urinary proteins can trigger an immune response and might be responsible for anaphylactic reactions. Immune reaction could also influence the development of the embryo and hinder normal

Kajihara et al. [18] proposed that some urinary-derived hCG (uhCG) impurities like EDN or ribonuclease 2 could influence inflammatory and immunological processes through regulation of apoptosis in endometrial cells and, therefore, directly influence embryo nesting and development during IVF. Considering that some patients undergo

lengthy and intensive treatment with uhCG, an effect cannot be excluded.

corpus luteum, thus suggesting that the effects observed were direct.

due to hCG or to a contamination from the formulation.

embryogenesis and embryo implantation in endometrium.

**18**

Formulations of hCG, both urinary and recombinant, contain contaminant proteins that originate from either starting material or has been introduced during the manufacturing process. The information about these contaminants cannot be identified on products' leaflets.

We could show that urinary-derived products contain a significant number of human proteins that obviously originate from the starting raw material—the human urine.

We think that this issue must be approached and discussed since the recombinant proteins show no such contamination and their use has been proven safe and effective.

Due to an important role played by hCG in embryo development in healthy subjects and embryo implantation during the IVF procedure, it is of great importance to thoroughly check the quality of the formulations and apply production steps for the best possible removal of all contaminant proteins from the final product and prevent possible adverse and allergic reactions, which might affect embryogenesis in general and embryo implantation in uterus.
