Amniotic sac—The membranous sac that surrounds the embryo and fills with watery fluid as pregnancy advances.
Breech birth—Birth of a baby bottom- or feet-first, instead of the usual head first delivery. This can add to labor and delivery problems because the baby's bottom doesn't mold a passage through the birth canal as well as the head.
Cervix—A small cylindrical organ, about an inch(2.54 cm) or so long and less than an inch around, that makes up the lower part and neck of the uterus. The cervix separates the body and cavity of the uterus from the vagina.
Embryo—The unborn child during the first eight weeks of its development following conception.
Gestation—The period from conception to birth, during which the developing fetus is carried in the uterus.
Perineum—The area between the thighs that lies behind the genital organs and in front of the anus.
Placenta—The organ that develops in the uterus during pregnancy and that links the blood supplies of mother and baby.
Cunningham, F. Gary, et.al. Williams Obstetrics. 20th ed. Stamford, CT: Appleton & Lange, 1997.