For a dermal puncture on an infant the maximum depth of the lancet should be

A depth of 3 mm exceeds the recommended maximum for a dermal puncture in infants. This increased depth raises the risk of penetrating beyond the dermis into deeper tissues, which could lead to complications such as hematoma formation or injury to underlying structures. Therefore, it is not appropriate for safe blood collection in infants.

A depth of 0.30 mm is insufficient for a dermal puncture. While it may reduce the risk of injury, it is likely too shallow to obtain an adequate blood sample, leading to the potential need for multiple punctures and increased discomfort for the infant.

Similarly, a depth of 0.20 mm is also too shallow for effective blood collection. This depth does not penetrate adequately into the dermis to access the capillary network needed for obtaining a blood sample, which can result in an unsuccessful attempt and increased anxiety for both the infant and caregiver.