Culturing more than three 2-PN stages in everyday practice a pilot study consistent with the embryo protection law

Background: The aim of this pilot study was to evaluate how many viable embryos develop when more than three two-pronuclei (2-PN) stages are cultured, and whether this can be used to predict and plan the viability of 2-PN stages. Methods: Patients undergoing their first or second in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycle were prospectively included in the first 6 months of 2010. The number of 2-PN stages to be cultured and the length of time they would be cultured was individually agreed upon with each couple. Results: Forty-four patients were treated in this individualized way. Per couple, an average of three to five 2-PN stages were cultivated for 3-5 days. After 5 days' culture, no viable embryos were identifiable for 12 patients, one viable embryo was found for 15 patients, and two vital embryos had developed for 15 patients. One further patient had three viable embryos and one had four. One preimplantation embryo for one patient and two preimplantation embryos for another patient were therefore cryoconserved. The pregnancy rate was 28% per embryo transfer. All cryoconserved embryos were transferred during a subsequent cycle. Conclusions: It is easily possible in individual cases to predict how many 2-PN stages will develop further to obtain a maximum of two viable embryos. The rate of so-called supernumerary embryos was acceptably low during this process, although these embryos were also transferred later as well.