Abortion: The termination of a pregnancy through the expulsion of the fetus from the uterus.

Abortion, spontaneous: Miscarriage that has not been induced artificially.

Afterbirth: The placenta and other tissues associated with fetal development that are expelled after the birth of an infant.

Albumin: A protein which if found in the urine of a pregnant woman can be a sign of pre-eclampsia.

Alpha fetoprotein: A substance produced by the fetus. High levels in a mother's blood can indicate a neural tube defect or multiple pregnancy.

Amino acid: A building block of protein which is used by the body to build muscle and other tissue.

Amniocentesis: A prenatal test in which a small amount of amniotic fluid is removed for analysis.

Amniotic fluid: The fluid that surrounds a developing fetus.

Amniotic sac: The bag in which the fetus and amniotic fluid are contained during pregnancy.

Anencephaly: A severe congenital defect in which the fetus has no brain.

Anesthesia: Medically induced loss of sensation. General anesthesia involves the entire body; local anesthesia involves only a particular area.

Anomaly: Malformation or abnormality of a body part.

Antibiotic: A drug used to combat infection.

Antibody: A protein produced by the immune system to destroy foreign substances.

Apgar scoring system: A method of evaluating a baby's health immediately after birth.

Apnea: A temporary involuntary cessation of breathing.

Areola: The pink or brown area of skin around the nipple of the breast.

Aspirate: To inhale liquid into the lungs, or to remove liquid from the lungs with a suction device.

Bilirubin: Pigment in the blood, urine, and bile that results from the normal breakdown of hemoglobin in the red blood cells.