Pregnant woman walkingAbout 8 percent of pregnant women in the U.S. smoke, according to new data released Wednesday by the Centers for Disease Control and Prevention.

Using birth certificate data from 2014, the researchers also found that one in 10 women smoked in the three months before getting pregnant, and only about a quarter of those women quit before becoming pregnant.

Smoking during pregnancy can lead to complications such as preterm birth and low birth weight. It can also increase the risk for sudden infant death syndrome.

According to the report, smoking during pregnancy was most prevalent among women ages 20 to 24, at 13 percent. American Indian and Alaska Native women were most likely to smoke while pregnant, making up 18 percent of smokers.

Smoking rates also varied by state, with 1.8 percent of California women and 27.1 percent of West Virginia women smoking while pregnant.

About one in five women who smoked during pregnancy quit by the third trimester, the report found. For women who smoked the entire pregnancy, they did smoke fewer cigarettes as the pregnancy progressed, from 13 a day before pregnancy down to 9 a day by the third trimester.