Pregnancy Acne: What’s the Best Treatment? – Mayo Clinic

Pregnancy acne isn’t a special form of acne. Some people simply seem to have trouble with acne during pregnancy. The likely culprit is an excessive production of oil (sebum) — which happens when the body produces greater amounts of certain hormones.

Source: https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/pregnancy-acne/faq-20058045