Pregnancy can cause acne flare-ups.

More Info: Acne can be triggered by a variety of things, hormones topping the list.  Just as the hormonal changes of puberty can trigger an outbreak, the hormonal changes experienced during pregnancy can have the same affect.  This is not the case for all women.  Some find that the hormonal changes that are experienced during pregnancy actually improve their acne. ["Acne fact sheet." womenshealth.gov]

How Do Hormones Affect Acne?

Sebum is a fatty substance that is secreted by the sebaceous glands that lubricates the hair and skin through the hair follicles.  Hormones stimulate the volume of the sebaceous glands and sebum secretion. [Zouboulis, 107] When too much sebum is produced, the hair follicles can become blocked creating a breeding ground for bacteria, which cause acne.

How Do Hormones Change During Pregnancy?

Hormones change during pregnancy as a result of the production of human chorionic gonadotropin (HGC). HCG causes levels of progesterone and estrogen to rise. Estrogen increases the strength and tone of the uterus in to prepare the muscles for the contractions of delivery.  Progesterone increases in the early stages of the fetus development to suppress contractions to prevent miscarriage slowly waning as the pregnancy progresses. ["Hormones During Pregnancy." Children's Hospital of Pittsburgh]

What Skin Conditions Are Common During Pregnancy?

Skin conditions that are common during pregnancy include acne, spider veins, striae gravidarum and chloasma. Striae gravidarum are stretch marks and occur in 60% or more of pregnant women.  Younger women and women who gain a significant amount of weight appear to experience stretch marks more severely.  Chloasma is an area of skin that is darker than the rest of the body. It appears on the face and usually fades a few months following delivery.