alpha-fetoprotein (AFP) - a protein produced by the fetus that is excreted into the amniotic fluid. Abnormal levels of alpha-fetoprotein may indicate brain or spinal cord defects, multiple fetuses, a miscalculated due date, or chromosomal disorders.

amniocentesis - a test performed to determine chromosomal and genetic disorders and certain birth defects. The test involves inserting a needle through the abdominal and uterine wall into the amniotic sac to retrieve a sample of amniotic fluid.

amniotic sac - a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with amniotic fluid - liquid made by the fetus and the amnion (the membrane that covers the fetal side of the placenta) that protects the fetus from injury and helps to regulate the temperature of the fetus.

E. coli O157:H7 (Also called E. coli or Escherichia coli.) - species of bacteria found in the intestines of man and healthy cattle; often the cause of urinary tract infections, diarrhea in infants, and wound infections.

genetic counseling - providing an assessment of heritable risk factors and information to patients and their relatives concerning the consequences of a disorder, the probability of developing or transmitting it, and ways in which it can be prevented, treated, and managed.

listeriosis - a food-borne illness transmitted by bacteria in contaminated food.

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

periodontal disease (Also called gum disease.) - serious bacterial infections that destroy the gums and the surrounding tissues of the mouth.

placenta - an organ, shaped like a flat cake, that only grows during pregnancy and provides a metabolic interchange between the fetus and mother. (The fetus takes in oxygen, food, and other substances and eliminates carbon dioxide and other wastes.)

prenatal diagnosis - used to diagnose a genetic disease or condition in the developing fetus.

quickening - mother's ability to feel the movement of the fetus for the first time.

trimester - a pregnancy is divided into phases, which are about three months each.

toxoplasmosis - an infection caused by a parasite that can lead to serious illness or death in the fetus.

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