This kind of tattoos are called Ainu. Tattooing has been designed quite differently in the past, and in some cultures, it retains its primary function and that is protection. Tattooing has been used for protection rather than decoration, particularly for protection during pregnancy and childbirth when the woman is exposed to many risks.
During pregnancy, the net-like pattern of the tattoo would be to extend through the stomach confidential, and the numbers god sometimes protected women during childbirth, were tattooed on their thighs. All this was intended to keep children healthy in the womb and to protect the mother and child during pregnancy and childbirth. Hey, if you do not have a doctor, you have to do something, right?