placenta accreta

placenta

[plah-sen´tah] (pl. placentas, placen´tae) (L.) an organ characteristic of true mammals during pregnancy, joining mother and offspring, providing endocrine secretion and selective exchange of soluble bloodborne substances through apposition of uterine and trophoblastic vascularized parts. See also afterbirth. adj., adj placen´tal.
In anatomic nomenclature the placenta consists of a uterine and a fetal portion. The chorion, the superficial or fetal portion, is surfaced by a smooth, shining membrane continuous with the sheath of the umbilical cord (amnion). The deep, or uterine, portion is divided by deep sulci into lobes of irregular outline and extent (the cotyledons). Over the maternal surface of the placenta is stretched a delicate, transparent membrane of fetal origin. Around the periphery of the placenta is a large vein (the marginal sinus), which returns a part of the maternal blood from the organ.
The major function of the placenta is to allow diffusion of nutrients from the mother's blood into the fetus's blood and diffusion of waste products from the fetus back to the mother. This two-way exchange takes place across the placental membrane, which is semipermeable; that is, it acts as a selective filter, allowing some materials to pass through and holding back others.
In the early months of pregnancy the placenta acts as a nutrient storehouse and helps to process some of the food substances that nourish the fetus. Later, as the fetus grows and develops, these metabolic functions of the placenta are gradually taken on by the fetal liver.
The placenta secretes both estrogens and progesterone. After birth of the infant the placenta is cast off from the uterus and expelled via the birth canal.placenta accre´ta one abnormally adherent to the myometrium, with partial or complete absence of the decidua basalis.battledore placenta one with the umbilical cord inserted at the edge.placenta circumvalla´ta one encircled with a dense, raised, white nodular ring, the attached membranes being doubled back over the edge of the placenta.placenta fenestra´ta one that has spots where placental tissue is lacking.placenta incre´ta placenta accreta with penetration of the myometrium.placenta membrana´cea one that is abnormally thin and spread over an unusually large area of the myometrium.placenta percre´ta placenta accreta with invasion of the myometrium to the peritoneal covering, sometimes causing rupture of the uterus.placenta pre´via low implantation of the placenta so that it partially or completely covers the cervical os. Percentages are used to designate the amount of obstruction; e.g., 100 per cent is total placenta previa, and 50 per cent indicates that about half the opening is obstructed. The condition occurs with greater frequency in women who have had multiple pregnancies or are over 35. The exact cause is not known.
With the onset of any contractions and cervical dilation, or when the cervix begins to dilate at the onset of labor and the upper and lower uterine segments differentiate, the placenta is stretched and pulled from the uterine wall, producing bleeding. The bleeding usually is abrupt and painless and may stop on its own. However, if it continues it can be life-threatening for the mother since it is maternal blood that is being lost. The life of the fetus is in jeopardy because of anoxia resulting from separation of the placenta from its blood supply.
Diagnosis can be established by ultrasonography or radiologic placentography. Once diagnosis is made, treatment will depend on the gestational age of the fetus and the percentage of placenta covering the cervical os. Cesarean delivery is recommended if 30 per cent or more of the opening is obstructed by the placenta. If there is minimal bleeding that stops on its own, the fetus is not in distress, and if the gestational age is such that continuing the pregnancy is necessary for delivery of a viable fetus, the pregnancy may be continued under careful monitoring in the hospital, or at home if the mother is able to stay in bed. However, if the life of the mother or fetus is threatened by continued and excessive bleeding, delivery is indicated.
Vaginal examinations are carried out in an operating room so that if hemorrhage does occur as a result of manipulation of the uterus, a cesarean section can be done immediately to remove the placenta, stop the bleeding, and deliver the child safely.Patient Care. Premature separation of the placenta is an emergency. The maternal signs are monitored every 15 minutes and blood loss is evaluated. Fetal heart tones also are monitored to detect fetal distress. The amount of bleeding is estimated and documented. Oxygen equipment should be at hand in the event signs of fetal distress indicate anoxia.
Postpartal hemorrhage and infection are more likely in women who have had placenta previa. Placement of the placenta in the lower segment predisposes to more bleeding because that portion of the uterus does not contract as forcefully as the upper segment. Additionally, the misplaced placenta has enlarged its bed to compensate for its poor location, so that there is a larger denuded area after delivery of the placenta. The same denuded area is also more susceptible to infection because it is located near the cervical opening where infectious organisms may enter.
Vaginal bleeding during pregnancy or labor is frightening for the mother. She will need reassurance and frequent explanations of what is happening to her throughout the period of monitoring and delivery. Some emotional stress can be alleviated by encouraging the mother to be aware of fetal movements and allowing her to listen to normal fetal heart sounds.placenta reflex´a one in which the margin is thickened, appearing to turn back on itself.placenta spu´ria an accessory portion without blood vessels connecting it with the main placenta.placenta succenturia´ta an accessory portion with an artery and a vein connecting it with the main placenta.

pla·cen·ta ac·cre·'ta

the abnormal adherence of the chorionic villi to the myometrium, associated with partial or complete absence of the decidua basalis and, in particular, the stratum spongiosum.
See also: placenta percreta.

pla·cen·ta ac·cre·ta

(plă-sen'tă ă-krē'tā) The abnormal adherence of the chorionic villi to the myometrium, associated with partial or complete absence of the decidua basalis and, in particular, the stratum spongiosum.

placenta accreta

A placenta with abnormally deep penetration of the CHORIONIC VILLI into the wall of the womb. After delivery of the baby, the placenta does not separate and come away as normal but is retained. HYSTERECTOMY is sometimes necessary.

单词	placenta accreta
释义	DictionarySeeplacenta placenta accreta placenta accreta [plə′sent·ə ə′krēd·ə] (medicine) A placenta that has partially grown into the myometrium of the uterus. placenta accreta placenta [plah-sen´tah] (pl. placentas, placen´tae) (L.) an organ characteristic of true mammals during pregnancy, joining mother and offspring, providing endocrine secretion and selective exchange of soluble bloodborne substances through apposition of uterine and trophoblastic vascularized parts. See also afterbirth. adj., adj placen´tal. In anatomic nomenclature the placenta consists of a uterine and a fetal portion. The chorion, the superficial or fetal portion, is surfaced by a smooth, shining membrane continuous with the sheath of the umbilical cord (amnion). The deep, or uterine, portion is divided by deep sulci into lobes of irregular outline and extent (the cotyledons). Over the maternal surface of the placenta is stretched a delicate, transparent membrane of fetal origin. Around the periphery of the placenta is a large vein (the marginal sinus), which returns a part of the maternal blood from the organ. The major function of the placenta is to allow diffusion of nutrients from the mother's blood into the fetus's blood and diffusion of waste products from the fetus back to the mother. This two-way exchange takes place across the placental membrane, which is semipermeable; that is, it acts as a selective filter, allowing some materials to pass through and holding back others. In the early months of pregnancy the placenta acts as a nutrient storehouse and helps to process some of the food substances that nourish the fetus. Later, as the fetus grows and develops, these metabolic functions of the placenta are gradually taken on by the fetal liver. The placenta secretes both estrogens and progesterone. After birth of the infant the placenta is cast off from the uterus and expelled via the birth canal.placenta accre´ta one abnormally adherent to the myometrium, with partial or complete absence of the decidua basalis.battledore placenta one with the umbilical cord inserted at the edge.placenta circumvalla´ta one encircled with a dense, raised, white nodular ring, the attached membranes being doubled back over the edge of the placenta.placenta fenestra´ta one that has spots where placental tissue is lacking.placenta incre´ta placenta accreta with penetration of the myometrium.placenta membrana´cea one that is abnormally thin and spread over an unusually large area of the myometrium.placenta percre´ta placenta accreta with invasion of the myometrium to the peritoneal covering, sometimes causing rupture of the uterus.placenta pre´via low implantation of the placenta so that it partially or completely covers the cervical os. Percentages are used to designate the amount of obstruction; e.g., 100 per cent is total placenta previa, and 50 per cent indicates that about half the opening is obstructed. The condition occurs with greater frequency in women who have had multiple pregnancies or are over 35. The exact cause is not known. With the onset of any contractions and cervical dilation, or when the cervix begins to dilate at the onset of labor and the upper and lower uterine segments differentiate, the placenta is stretched and pulled from the uterine wall, producing bleeding. The bleeding usually is abrupt and painless and may stop on its own. However, if it continues it can be life-threatening for the mother since it is maternal blood that is being lost. The life of the fetus is in jeopardy because of anoxia resulting from separation of the placenta from its blood supply. Diagnosis can be established by ultrasonography or radiologic placentography. Once diagnosis is made, treatment will depend on the gestational age of the fetus and the percentage of placenta covering the cervical os. Cesarean delivery is recommended if 30 per cent or more of the opening is obstructed by the placenta. If there is minimal bleeding that stops on its own, the fetus is not in distress, and if the gestational age is such that continuing the pregnancy is necessary for delivery of a viable fetus, the pregnancy may be continued under careful monitoring in the hospital, or at home if the mother is able to stay in bed. However, if the life of the mother or fetus is threatened by continued and excessive bleeding, delivery is indicated. Vaginal examinations are carried out in an operating room so that if hemorrhage does occur as a result of manipulation of the uterus, a cesarean section can be done immediately to remove the placenta, stop the bleeding, and deliver the child safely.Patient Care. Premature separation of the placenta is an emergency. The maternal signs are monitored every 15 minutes and blood loss is evaluated. Fetal heart tones also are monitored to detect fetal distress. The amount of bleeding is estimated and documented. Oxygen equipment should be at hand in the event signs of fetal distress indicate anoxia. Postpartal hemorrhage and infection are more likely in women who have had placenta previa. Placement of the placenta in the lower segment predisposes to more bleeding because that portion of the uterus does not contract as forcefully as the upper segment. Additionally, the misplaced placenta has enlarged its bed to compensate for its poor location, so that there is a larger denuded area after delivery of the placenta. The same denuded area is also more susceptible to infection because it is located near the cervical opening where infectious organisms may enter. Vaginal bleeding during pregnancy or labor is frightening for the mother. She will need reassurance and frequent explanations of what is happening to her throughout the period of monitoring and delivery. Some emotional stress can be alleviated by encouraging the mother to be aware of fetal movements and allowing her to listen to normal fetal heart sounds.placenta reflex´a one in which the margin is thickened, appearing to turn back on itself.placenta spu´ria an accessory portion without blood vessels connecting it with the main placenta.placenta succenturia´ta an accessory portion with an artery and a vein connecting it with the main placenta. pla·cen·ta ac·cre·'ta the abnormal adherence of the chorionic villi to the myometrium, associated with partial or complete absence of the decidua basalis and, in particular, the stratum spongiosum. See also: placenta percreta. pla·cen·ta ac·cre·ta (plă-sen'tă ă-krē'tā) The abnormal adherence of the chorionic villi to the myometrium, associated with partial or complete absence of the decidua basalis and, in particular, the stratum spongiosum. placenta accreta A placenta with abnormally deep penetration of the CHORIONIC VILLI into the wall of the womb. After delivery of the baby, the placenta does not separate and come away as normal but is retained. HYSTERECTOMY is sometimes necessary.
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