Fetal alcohol spectrum disorders are caused by a mother drinking alcohol during pregnancy. Surveys from the United States found that about 10% of pregnant women drank alcohol in the past month, and 20% to 30% drank at some point during the pregnancy. About 3.6% of pregnant American women are alcoholics. The risk of FASD depends on the amount consumed and the frequency of consumption as well as at what point in pregnancy the alcohol was consumed. Other risk factors include older age of the mother, smoking, and poor diet. There is no known safe amount or time to drink alcohol during pregnancy. While drinking small amounts does not cause abnormalities in the face, it may cause behavioral issues. Alcohol crosses the blood–brain barrier and both directly and indirectly affects a developing fetus. Diagnosis is based on the signs and symptoms in the person.