Dictionary

pleurodynia See Bornholm disease.

plumbism See lead poisoning.

placebo A sugar pill or any other inactive substance that is given instead of medication. In a controlled clinical trial, one group may be given a medication and another group a placebo, to learn whether a difference in treatment response is due to the medication, the power of suggestion, or other factors. See also placebo…

placebo response A positive medical response to taking a placebo, as if it were an active medication.

placenta A temporary organ that joins the mother and fetus, transferring oxygen and nutrients from the mother to the fetus and permitting the release of carbon dioxide and waste products from the fetus. The placenta is roughly disk-shaped, and at full term it measures about 7 inches in diameter and slightly less than 2 inches…

placenta, accessory A condition in which there is an extra placenta that is separate from the main placenta. Also known as a succenturiate or supernumerary placenta.

placenta, low See placenta previa.

placenta, succenturiate See placenta, accessory.

placenta, supernumerary See placenta, accessory.

placenta accreta The abnormal adherence of the chorion of the placenta to the myometrium of the uterus. Normally there is tissue intervening between the chorionic villi and the myometrium, but in placenta accreta, the vascular processes of the chorion grow directly in the myometrium. Placenta accreta can progress into placenta percreta.

placenta percreta A condition in which the placenta invades the uterine wall. In placenta percreta, the vascular processes of the chorion (chorionic villi), a fetal membrane that enters into the formation of the placenta, can invade the full thickness of the myometrium. This can cause an incomplete rupture of the uterus. The chorionic villi can…

placenta previa A condition in which the placenta is implanted near the outlet of the uterus, so that at the time of delivery the placenta precedes the baby. Placenta previa can cause painless bleeding in the last trimester of pregnancy, and it may be a reason to perform a C-section. Also known as low placenta.