Braxton Hicks contractions: Painless, irregular contractions of the pregnant uterus, beginning during the first trimester and increasing in frequency as the pregnancy advances.
Cervix: the neck of the uterus.
Contraction: rhythmic tightening of the uterus, usually causing the cervix to dilate and allow the passage of the baby. In labor contractions get stronger, closer together and longer.
Dilatation: the enlarging of the cervix to 10 centimeters.
Effacement: the thinning of the cervix. Your cervix starts out being two inches long, and 50% effaced would be a 1 inch cervix.
Labor: The period of contractions that change the cervix and ends with the birth of your baby.
Lightening: Your baby changing positions in the uterus before labor, usually described as the baby "dropping." First time moms can see this as soon as 4-6 before their due date, whole other moms will notice this not until labor begins.
Placenta: The organ within the pregnant uterus through which the fetus derives its nourishment; at term it averages one-sixth the weight of the fetus; is disk-shaped, about 2.5 cm thick, and 17.5 cm in diameter.
Station: How far the baby is "down" in the pelvis. Measured in negative and positive numbers. -5 is a floating baby, 0 station is said to be engaged in the pelvis, and +5 is crowning.
Uterus: Female reproductive organ that weighs about 2-3 ounces and is about the size of a small woman's fist prior to pregnancy. During pregnancy this organ becomes 10 by 14 inches and weighs in at about 2-3 pounds. This is where a normal pregnancy takes place.