Vitamin and mineral supplementation during pregnancy is a common practice in the United States, but is often unnecessary. An assessment of dietary practices is recommended for all women to evaluate the need for improved diet or vitamin and mineral supplementation. Most women do not receive enough folic acid from dietary sources and should take a folic acid supplement in the preconception period to minimize their risk of neural tube defect. Iron supplementation is recommended in the second and third trimester. A multivitamin and mineral supplement is recommended during pregnancy for women who do not ordinarily consume an adequate diet and for women in high-risk categories, such as multifetal gestation, heavy cigarette smokers, and alcohol and drug abusers.