areola - the pigmented areas around each breast's nipple.

embryo - the fetus is first called an embryo during the first eight weeks after conception.

fetus - an unborn baby from the eighth week after fertilization until delivery.

folic acid - a nutrient found in some green leafy vegetables, nuts, beans, citrus fruits, fortified breakfast cereals, and some vitamin supplements. Folic acid can help reduce the risk of birth defects of the brain and spinal cord (also called neural tube defects).

neural tube defects - defects of the fetal brain or spine.

Rh disease - complications resulting from incompatibility between the blood types of the mother and baby.

rubella (Also called German measles.) - a contagious, viral disease that can cause miscarriage or birth defects if contracted by the mother during pregnancy.

teratogen - an agent, which can cause a birth defect. It is usually something in the environment that the mother may be exposed to during her pregnancy.

trimester - a pregnancy is divided into phases, each approximately three months in length.

ultrasound - a diagnostic imaging technique that uses high-frequency sound waves to create an image of the fetus' body and organs and the surrounding tissues.

uterus (Also called the womb.) - a hollow, pear-shaped organ located in a woman's lower abdomen, between the bladder and the rectum, that sheds its lining each month during menstruation and in which a fertilized egg (ovum) becomes implanted and the fetus develops.