During which months of fetal life do friction ridges form?

The formation of friction ridges, which are the unique patterns found on the fingertips, palms, and soles of the feet, occurs primarily during the 3rd and 4th months of fetal development. Around this time, the skin layers are developing, and the papillary dermis is forming into ridges that create the characteristic patterns.

The 3rd and 4th months are crucial for the establishment of these patterns because the physiological processes that lead to the creation of friction ridges are happening at a rapid pace during this period. It's during these months that the environment inside the uterus allows for the skin to develop these ridges in response to interactions with the surrounding structures.

Friction ridge formation is generally completed by the end of the 4th month, and any subsequent growth or changes to the ridges are typically due to skin growth rather than the formation of new ridges. This means that while growth continues, the fundamental patterns of friction ridges are already established during the earlier months.