Effect of vitrification versus slow freezing of human day 3 embryos on β-hCG levels

Abstract

Purpose The study was designed to investigate the effect of vitrification and slow freezing for the cryopreservation of human day 3 embryos on serum β-hCG levels in pregnancies established after frozen embryo transfer (FET). Methods Of the 1384 FET cycles initiated, 1131 embryo transfers met study criteria and assigned to one of two groups: 797 slow-freezing embryo transfers or 334 vitrified embryo transfers. Median values of β-hCG and outcome of all pregnancies were compared between the two groups. Predictive values of serum β-hCG on day 12 after embryo transfer for establishing ongoing pregnancy and pregnancy failure were determined by receiver operating characteristic (ROC) curve analysis. Results In the slow-freezing group, 383 ongoing pregnancies occurred (48.1 %), and transfers of vitrified embryos resulted in 154 pregnancies (46.1 %). Median β-hCG values (279.2 IU/L) for ongoing pregnancies after transfer of vitrified embryos were significantly lower than that of slow frozen embryos (320.5 IU/L). The median values of β-hCG for singleton in the two groups was statistically significant (P<0.05). For slowfreezing embryo transfers, the cut-off value of β-hCG in predicting ongoing pregnancy was 147 IU/L (sensitivity 88.3 %, specificity 80.7 %). For vitrified embryo transfers, the value was 135 IU/L (sensitivity 84.4 %, specificity 76.3 %). Conclusions Day 12 β-hCG levels after FET are significantly affected by the methods of embryo cryopreservation for ongoing pregnancies. Furthermore, when using β-hCG cutoff value to assess pregnancy outcome, the cryopreservation methods should be taken into account.

Slow freezing should not be totally substituted by vitrification when applied to day 3 embryo cryopreservation: an analysis of 5613 frozen cycles

“…Several studies have shown similar pregnancy and implantation rates between slow freezing and vitrification [13,27]. Vitrified embryo transfer is associated with lower hCG concentrations on day 12 post-embryo transfer compared with slow freezing embryo transfer [18]. In the current study, a higher implantation rate in slow freezing than in vitrification was found.…”

“…Slow freezing of day 3 embryos was performed as described by Edgar et al [17], which involved a slow controlled freezing and thawing protocol with propanediol/sucrose (Freezing Kit; Irvine Scientific, Santa Ana, CA, USA) as the cryoprotectant, as described previously [18]. For vitrification of embryos, an open system was selected based on previous studies for its safety [19,20].…”

“…In our center, three main types of clinical protocols were used for endometrial preparation: the natural cycle, hormone replacement cycle, or human menopausal gonadotropin (HMG)-stimulated cycles [18]. For patients with regular menstrual cycles, the natural cycle was proposed and embryo transfer was performed 3 days after ovulation, or 4.5 days after the luteinizing hormone peak.…”

Peer Review #2 of "The effect on twinning rate of transferring double vitrified-warmed embryos in women of advanced reproductive age: a retrospective study (v0.2)"

“…The ovarian stimulation and IVF procedures have been previously described (Xue et al 2014;Xue et al 2018). Briefly, embryo culture with sequential media was carried out as follows: fertilization was performed in fertilization medium (G-IVF, Vitrolife Sweden AB, Sweden) containing 10% serum substitute supplement (SSS, Irvine Scientific, Santa Ana, CA).…”

“…The following morning, the oocytes were individually placed in microdrops in cleavage medium (G-1, Vitrolife Sweden AB, Sweden) with 12 % SSS and incubated in incubators at 37℃ with 6 % CO 2 , 5% O 2 and 89% N 2 for 48 h before being frozen. Morphological assessment of embryos was based on the number of blastomeres and the proportion of cytoplasmic fragments and the uniformity of blastomeres (Xue et al 2014).…”