Improved implantation rate after chemical removal of the zona pellucida.
OBJECTIVE
To evaluate the implantation rate achieved after chemical removal of the zona pellucida from day 5 human in vitro-derived embryos.


METHODS
Prospective, randomized, controlled study.


METHODS
A tertiary care infertility clinic.


METHODS
Two hundred fifty-seven patients undergoing IVF with transfer of morulas or blastocysts on day 5 after oocyte retrieval. All patients had had at least two previous implantation failures.


METHODS
Chemical removal of zona pellucida by using acidic Tyrode's solution vs. no removal (controls).


METHODS
Clinical pregnancy rate and implantation rate per transfer.


RESULTS
Embryos without zona pellucida implanted at nearly twice the rate of control embryos (15.7% vs. 27.5%). The pregnancy rate was also significantly higher in the zona pellucida-free group than the control group (31.0% vs. 46.1%). Removal of zona pellucida was most effective in embryos with delayed development, which reached the morula or early cavitating stage on day 5 of in vitro culture (implantation rate, 12.1% vs. 25.7%).


CONCLUSIONS
Chemical removal of zona pellucida from day 5 in vitro cultured human embryos is an effective and safe method of significantly improving the implantation rate, especially of embryos with delayed development.
Jelinkova
Ladislava
L
Gynecology and Obstetrics Department and General Faculty Hospital, Charles University, Prague, Czech Republic. ljeli@seznam.cz
Pavelkova
Jana
J
Strehler
Erwin
E
Paulus
Wolfgang
W
Zivny
Jaroslav
J
Sterzik
Karl
K
D001755:Blastocyst / Q000502:physiology; D010064:Embryo Implantation; D005260:Female; D006801:Humans; D007552:Isotonic Solutions / Q000494:pharmacology; D011247:Pregnancy; D011446:Prospective Studies; D020554:Sperm Injections, Intracytoplasmic; D015044:Zona Pellucida / Q000187:drug effects / Q000502:physiology*
D007552:Isotonic Solutions; C037692:Tyrode's solution