Blastocyst development in single medium with or without renewal on day 3: a prospective cohort study on sibling donor oocytes in a time-lapse incubator.

OBJECTIVE

To evaluate the efficiency of using a continuous (one-step) protocol with a single medium for the culture of human embryos in a time-lapse incubator (TLI).

DESIGN

Prospective cohort study on sibling donor oocytes.

SETTING

University-affiliated in vitro fertilization (IVF) center.

PATIENT(S): Embryos from 59 patients.

INTERVENTION(S): Culture in a TLI in a single medium with or without renewal of the medium on day-3.

MAIN OUTCOME MEASURE(S): Embryo morphology and morphokinetic parameters, clinical pregnancy, take-home baby rate, and perinatal outcomes.

RESULT(S): The blastocyst rates (68.3 vs. 66.8%) and the proportion of good-quality blastocysts (transferred plus frozen) obtained with the two-step (80.0%) protocol were statistically significantly similar to those obtained in the one-step protocol (72.2%). Similarly, morphokinetic events from early cleavage until late blastocyst stages were statistically significantly equivalent between both groups. No differences were found either in clinical pregnancy rates when comparing pure transfers performed with embryos selected from the two-step (75.0%), one-step (70.0%, respectively), and mixed (57.1%) groups. A total of 55 out of 91 embryos transferred implanted successfully (60.4%), resulting in a total of 37 newborns with a comparable birth weight mean among groups.

CONCLUSION(S): Our findings support the idea that in a TLI with a controlled air purification system, human embryos can be successfully cultured continuously from day 0 onward in single medium with no need to renew it on day-3. This strategy does not affect embryo morphokinetics or development to term and offers more stable culture conditions for embryos as well as practical advantages and reduced costs for the IVF laboratory.