Humidified culture in a dry incubator improves culture performance.

OBJECTIVE

This study aimed to determine whether localized humidification within a dry incubator could mitigate increased osmotic pressure in the culture medium and improve embryo development and clinical outcomes.

METHODS

In vitro culture and pregnancy outcomes were retrospectively compared between a dry incubator group (K-dry) and a conventional humidified incubator group (WJ). In addition, a K-humidified group was prospectively established by adding 4 mL of human tubal fluid medium outside the wells in a dry incubator to assess whether localized humidification improved outcomes compared with conventional dry conditions.

RESULTS

In the two-group comparison, the WJ group had significantly higher rates of good-morphology day 3 embryos, blastocyst formation, and good-morphology blastocysts than the K-dry group (p<0.05). In multivariate analysis, dry culture conditions were independently associated with poorer developmental outcomes. In the three-group comparison, the K-humidified group had a significantly higher rate of good-morphology day 3 embryos than the K-dry group (p=0.011) and did not differ significantly from the WJ group. Clinical pregnancy and ongoing pregnancy rates did not differ significantly across the study groups.

CONCLUSION

Dry culture conditions may compromise embryo quality through osmotic stress. Localized humidification within a dry incubator was associated with improved early embryo development and increased the number of embryos suitable for transfer or cryopreservation, with comparable performance to a conventional humidified incubator. However, once embryos reached a transferable blastocyst stage, implantation potential appeared to be driven primarily by intrinsic embryo competence rather than by the prior culture environment.