Effect of developmental stage of embryo at freezing on pregnancy outcome of frozen–thawed embryo transfer
Authors: Salumets, Andres; Tuuri, Timo; Mäkinen, Sirpa; Vilska, Sirpa; Husu, Lea; Tainio, Ritva; Suikkari, Anne‐Maria
Source: Human Reproduction, Volume 18, Number 9, September 2003 , pp. 1890-1895(6)
Publisher: Oxford University Press
Abstract:BACKGROUND: The study aim was to investigate the impact of the developmental stage of embryos on pregnancy outcome of frozen embryo transfer (FET). METHODS: The survival rates of embryos after thawing and pregnancy outcome following FET were compared retrospectively between three cryopreservation strategies utilizing either zygote, day 2 or day 3 embryo freezing. RESULTS: A total of 4006 embryos was analysed in 1657 thaw cycles. The highest (P < 0.0001) survival rate (all cells survived) was observed for zygotes (86.5%), followed by day 2 (61.7%) and day 3 (43.1%) embryos. FET was performed in 1586 (95.7%) of all thaw cycles, resulting in overall clinical pregnancy and implantation rates of 20.7 and 14.2% respectively. The delivery rate per transfer was 16.5%, and live birth rate per transferred embryo 11%. There were no significant differences in clinical pregnancy, implantation, delivery and birth rates between frozen zygote, day 2 and 3 embryo transfers. However, an elevated miscarriage rate was observed in the day 3 group (45%) compared with zygotes (21.3%; P = 0.049) and day 2 embryos (18.3%; P = 0.004). The overall efficacy of FET (birth rate per thawed embryo) was 7.3%. The efficacy was lower in day 3 group (4.2%) than in the zygote (7.1%; P = 0.082) and day 2 (7.6%; P = 0.027) groups. CONCLUSIONS: The developmental stage of embryos at freezing has a profound effect on their post‐thaw survival, but seems to have little effect on rates of clinical pregnancy, implantation, delivery and birth after FET. The elevated miscarriage rate for day 3 frozen embryo transfers may be caused by damage during freeze–thaw procedures. The low survival rate and elevated miscarriage rate were both responsible for a reduced overall efficacy for day 3 FET when compared with zygotes and day 2 embryos.
Document Type: Research Article
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Publication date: September 2003
- Human Reproduction features full-length, peer-reviewed papers reporting original research, clinical case histories, as well as opinions and debates on topical issues. Papers published cover the scientific and medical aspects of reproductive physiology and pathology, endocrinology, andrology, gonad function, gametogenesis, fertilization, embryo development, implantation, pregnancy, genetics, genetic diagnosis, oncology, infectious disease, surgery, contraception, infertility treatment, psychology, ethics and social issues. The highest scientific and editorial standard is maintained throughout the journal along with a rapid rate of publication.