Linea nigra and other skin changes in pregnancy

The linea nigra — a dark vertical line running from your navel to your pubic bone — is one of the most common and benign skin changes of pregnancy, appearing in more than 75% of pregnant women usually around week 20. It's caused by increased melanin production driven by pregnancy hormones and fades gradually over several months postpartum. The same hormones can cause melasma (dark patches on the face, sometimes called the 'mask of pregnancy'), darkening of the areolas and nipples, and the appearance of skin tags.

Sunscreen helps prevent melasma from darkening further. Stretch marks — caused by skin stretching faster than collagen can keep up — affect up to 90% of women; genetics is the biggest predictor of whether you'll get them.