Baby Acne. The baby acne is a common event that reflects hormones transferred during the pregnancy. While the baby is floating in moisture, the skin is will not respond, but within 1-3 weeks after birth they break out for many weeks until the hormone levels drop & the acne disappears. Keeping the skin clean ; avoiding irritating soaps helps If it persists > 3mo see the doc.
Not unusual. It would be uncommon for it NOT to spread. While baby floated in the fetal waters, it had a different skin environment. Now that it is outside & faces drying air and occasional washing the changes brought by pregnancy hormones come out. It usually starts at a week, peaks around 4-6 and begins to fade by 8-10. Keep it clean & it will pass.