High humidity in an incubator can have several effects:

1. Improper hatching: High humidity levels can cause eggs to become over-saturated with moisture, leading to improper hatching or hatching failures.
2. Growth of bacteria and mold: High humidity can also create an environment conducive to the growth of harmful bacteria and mold, which can contaminate the eggs and cause illness in the developing embryos.
3. Condensation: High humidity can also cause condensation to form on the walls of the incubator, which can cause temperature fluctuations and affect the overall stability of the incubation environment.

Therefore, it’s important to maintain proper humidity levels in an incubator to ensure proper hatching and healthy development of the embryos.