Assisted hatching improves implantation rates on cryopreserved–thawed embryos. A randomized prospective study

• Published in: Human reproduction (Oxford) Vol. 19; no. 10; pp. 2258 - 2262
• Main Authors: Gabrielsen, A., Agerholm, I., Toft, B., Hald, F., Petersen, K., Aagaard, J., Feldinger, B., Lindenberg, S., Fedder, J.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01-10-2004; Oxford Publishing Limited (England)
• Subjects: acidic Tyrode's solution; Administration, Topical; Adult; assisted hatching; Biological and medical sciences; Birth control; Cryopreservation; cryospreserved–thawed; Embryo Implantation; Embryo Transfer; Female; Fertilization in Vitro; Gynecology. Andrology. Obstetrics; Humans; implantation rates; Isotonic Solutions - administration & dosage; Isotonic Solutions - therapeutic use; Male; Medical sciences; Pregnancy; Prospective Studies; Sperm Injections, Intracytoplasmic; Sterility. Assisted procreation; Treatment Outcome; Zona Pellucida - drug effects; implantation rates; acidic Tyrode's solution; cryospreserved–thawed; assisted hatching; pregnancy; Human; Embryo; Randomization; Ovum implantation; Cryopreservation; acidic Tyrode's solution/assisted hatching/cryospreserved-thaed/implantation rates/pregnancy; Assisted procreation; Clinical trial; Thawing
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/deh434

BACKGROUND: Focus on the hatching process has so far been in the field of fresh embryos. Cryopreserved–thawed embryos have a lower rate of pregnancy than fresh embryos, which might be due to hardening of the zona pellucida. METHODS: During a 2 year period, a prospective randomized study enrolling 253 cryopreserved–thawed cycles was performed on day 2 embryos. Pseudorandomization to assisted hatching or a control group was done on the basis of even and odd dates for thawing. One hour before embryo transfer, hatching was carried out using acidic Tyrode's solution. RESULTS: Among 136 embryos exposed to assisted hatching, 11.4% (30) were implanted compared with only 5.8% (13) of 117 embryos not exposed to assisted hatching (P<0.05, χ2 test). No difference in the rate of clinical pregnancy and positive serum HCG was observed between the two groups. Very few women >38 years old were included in the study, and no significant difference according to age could be found between the groups. CONCLUSIONS: These results show that assisted hatching using acidic Tyrode's solution increases the implantation rate of cryopreserved–thawed embryos (P<0.05).