The effect of long zona dissection using ICSI pipettes for mechanical assisted hatching in vitrified-thawed blastocyst transfers.

OBJECTIVE: To investigate the effect of long zona dissection (LZD) compared with partial zona dissection (PZD) using ICSI pipettes for mechanical assisted hatching (AH) in vitrified-thawed blastocyst transfers.

DESIGN: Prospective study.

SETTING: University IVF clinic.

PATIENT(S): A total of 120 women ≦ 38 years old undergone vitrified-thawed blastocyst transfers with LZD or PZD.

INTERVENTION(S): The culture of all pronucleate embryos to the blastocyst stage and the selection of blastocysts ≧ grade 3BB (Gardner and Schoolcraft score), followed by vitrified-thawed blastocyst transfers with LZD (n = 60) or with PZD (n = 60)

MAIN OUTCOME MEASURE(S): Complete hatching rates, implantation rates, pregnancy rates.

RESULT(S): At 5 h after thawing, complete hatching rates of blastocysts were significantly higher in LZD group compared with PZD group, 52.4 % vs. 31.8 % (P = 0.001). Implantation and clinical pregnancy rates were significantly higher in LZD group compared with PZD group, 40.9 % vs. 25.7 % and 63.0 % vs. 40.0 %, respectively (P = 0.010, P = 0.011).

CONCLUSION(S): LZD using ICSI pipettes for mechanical AH improves significantly complete hatching, implantation and pregnancy rates in vitrified-thawed blastocyst transfers.