Article
Predictive value of serum HCG concentrations in pregnancies achieved after single fresh or vitrified-warmed blastocyst transfer

https://doi.org/10.1016/j.rbmo.2017.05.011Get rights and content

Abstract

Possible differences between serum HCG levels in pregnancies achieved after transfer of a single fresh or a vitrified-warmed blastocyst were evaluated. Out of 1130 single blastocyst transfers resulting in positive HCG results, 789 were single fresh blastocyst transfers and 341 single vitrified-warmed blastocyst transfers. The initial serum HCG levels of 869 clinical intrauterine pregnancies were evaluated, 638 after the transfer of a single fresh blastocysts and 231 after the transfer of a single vitrified-warmed blastocysts. The HCG levels from cycles resulting in a clinical intrauterine pregnancy were significantly higher after the transfer of a single vitrified-warmed blastocyst (383 ± 230 IU/l) versus a fresh transfer (334 ± 192 IU/l; P = 0.01). Threshold values for predicting a clinical pregnancy for a fresh blastocyst were 111 IU/l and for a vitrified-warmed blastocyst 137 IU/l. Our study shows that the overall beta-HCG levels are comparable after the transfer of a fresh or vitrified-warmed blastocyst, suggesting that vitrification most probably does not affect the ability of the embryos to produce beta-HCG. This study further shows that when clinicians counsel patients, they should take into account that higher HCG levels are needed after a vitrified-warmed blastocyst transfer to predict a clinical intrauterine pregnancy.

Introduction

Transfer of a single embryo is important in reducing the occurrence of multiple pregnancies. This is made possible by the increasing use of single embryo transfer and improving embryo cryopreservation for supernumerary embryos. It is imperative that the technique of cryopreservation minimally affects the viability and potency of the embryos. Transfer of vitrified embryos has been shown to be associated with a similar pregnancy outcome compared with that of fresh embryo (Feng et al, 2012, Takahashi et al, 2005), even when a single embryo is transferred (Roy et al., 2014).

HCG dimer is secreted from the syncytiotrophoblast as early as 6–8 days after fertilization, and may serve as a marker for embryo viability (Butler et al, 2013, Rull, Laan, 2005). It is known that HCG levels are correlated with pregnancy outcome (McCoy et al, 2009, Shamonki et al, 2009). Therefore, it is important to evaluate whether embryo vitrification followed by warming has an effect on the developmental potential of the embryo and its ability to produce and secrete HCG. In one study, serum HCG levels in pregnancies after transfer of a cryopreserved embryo was lower than those after fresh embryo transfer (Sites et al., 2015). Yet, the study numbers were small, cleavage and blastocyst embryos were included and various methods of cryopreservation were applied, including slow freezing and vitrification.

Transfer of more than one embryo makes it impossible to evaluate the true contribution of the embryo in the very early stages of development. It is possible that, in cases in which multiple embryos are transferred (more than one implant), only one embryo survives, resulting in a singleton clinical pregnancy and live birth. As expected, multiple implantations are associated with higher initial levels of HCG (Urbancsek et al, 2002, Singh et al, 2013). The vanishing twin phenomenon is reported to be as high as 10%, undoubtedly affecting the initial level of HCG measured in the maternal serum (Poikkeus et al., 2007).

The aim of the present study was to evaluate initial serum HCG levels after transfer of a single fresh blastocyst embryo or of a single vitrified-warmed blastocyst embryo.

Section snippets

Materials and methods

All fresh and vitrified-warmed single blastocyst transfers (SBT) carried out between January 2010 and December 2014 at the reproductive unit of the McGill University Health Center (MUHC) in Montreal, Canada were analysed. Only SBT of day 5 fresh and vitrified-warmed embryos from non-donor oocytes were included. For standardization purposes, only serum HCG levels drawn 11 days after the transfer of either fresh or vitrified-warmed blastocyst embryos were included. Day 11 after transfer was

Results

Of a total of 4821 non-donor blastocyst transfers, 2015 resulted in a positive serum HCG. After including only HCG results drawn 11 days after embryo transfer for fresh and vitrified-warmed cycles, 1144 cycle transfers were available for analysis. Two multiple gestations resulting from a single vitrified-warmed blastocyst embryo and 12 multiple gestations from a single fresh blastocyst embryo transfer were excluded from the analysis.

A total of 789 pregnancies were achieved after the transfer of

Discussion

In the present study, the initial HCG levels after the transfer of single fresh or single vitrified-warmed blastocyst were evaluated. Our study shows that the overall beta-HCG levels are comparable after the transfer of a fresh or vitrified-warmed blastocyst. This suggests that the vitrification process most probably does not affect the ability of the embryos to produce beta-HCG (McCoy et al, 2009, Singh et al, 2013). This is further supported by the reports of equivalent and even superior

Galia Oron, MD, completed her Obstetrics and Gynaecology residency in 2010 and postgraduate training in reproductive endocrinology and infertility, with excellence, at McGill University, Canada, in 2014. Her special research interests are the effect of growth differentiation factors on maturation of human ovarian follicles and IVF pregnancy outcomes.

Key message

Initial beta-HCG levels are comparable after the transfer of a single fresh or vitrified-warmed blastocyst; therefore, the

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    Galia Oron, MD, completed her Obstetrics and Gynaecology residency in 2010 and postgraduate training in reproductive endocrinology and infertility, with excellence, at McGill University, Canada, in 2014. Her special research interests are the effect of growth differentiation factors on maturation of human ovarian follicles and IVF pregnancy outcomes.

    Key message

    Initial beta-HCG levels are comparable after the transfer of a single fresh or vitrified-warmed blastocyst; therefore, the vitrification process probably does not affect the ability of the embryos to produce HCG. Significantly higher beta-HCG levels, however, are required to predict clinical pregnancy after the transfer of a vitrified-warmed blastocyst.

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