A new method to rescue embryos contaminated by bacteria.

Objective: To report a case of successful pregnancy involving embryos that wereaffected by bacterial contamination.

Design: A case report.

Setting: Academic assisted reproductive center.

Patients: A 31-year-old infertile patient with obstructed fallopian tubes facing bacterial contamination in her embryos during in vitro fertilization.

Interventions: The zona pellucida (ZP) of the embryos that was contaminated by bacteria was removed by acidic Tyrode's solution. The ZP-free embryos were then cultured in a time-lapse culture dish with 1 zygote per well until day 5 when a single ZP-free blastocyst was selected for transfer.

Main Outcome Measures: The rate of obtaining embryos without recurrence of bacterial contamination and the developmental potential of the embryos.

Results: Twenty oocytes were retrieved and were coincubated with sperm in vitro overnight. A total of 9 zygotes with 2 pronuclei and 3 zygotes with 1 pronucleus were obtained. Unfortunately, all zygotes were contaminated by the bacteria. The ZP of 7 zygotes were removed using acidic Tyrode's solution (ZP-free group), whereas the remaining 5 zygotes and 3 metaphase II (MII) stage oocytes were washed with G-1 PLUS medium multiple times (washing treatment group). In the washing treatment group, all embryos experienced recontamination on day 2 and were dead by day 3. In the ZP-free group, 2 embryos were found to be recontaminated on day 2. The remaining 5 embryos that stayed uncontaminated were selected for blastocyst culture. On day 5, 2 of the cultured embryos developed into blastocysts. One blastocyst was transferred during the fresh cycle, and the other was vitrified. A single intrauterine gestation was confirmed 4 weeks after the transfer. At the time of writing this article, the patient was 30 weeks pregnant without any occurrence of intrauterine infection during pregnancy.

Conclusions: Zona pellucida removal is a safe and effective method to rescue embryos contaminated with bacteria.