what can cause linea nigra
Causes of Linea Nigra. Pregnancy hormones are responsible for many skin changes during pregnancy, including linea nigra. Increased melanocyte stimulating hormone can cause darker nipples and areolas, as well as freckles. Linea nigra is not a painful condition and poses no threat to you or your baby. There is no physical reason for the line to appear other than indicating that the baby is coming.