| placenta previa | <obstetrics> The anatomic positioning of the placenta over the cervical os (opening to the birth canal). This is an important cause of painless third trimester bleeding in the pregnant female. Many cases of placenta previa will require cesarean section delivery. (31 Dec 1997) |
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| placenta previa centralis | Placenta previa in which the placenta entirely covers the internal os of the cervix. Synonym: central placenta previa, total placenta previa. (05 Mar 2000) |
| placenta previa marginalis | Placenta previa in which the placenta comes to the margin of, but does not occlude, the internal os of the cervix. (05 Mar 2000) |
| placenta previa partialis | Placenta previa in which the internal os of the cervix is partially covered by placental tissue. (05 Mar 2000) |
| central placenta previa | Placenta previa in which the placenta entirely covers the internal os of the cervix. Synonym: central placenta previa, total placenta previa. (05 Mar 2000) |
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| spontaneous correction of placenta previa | The upward "migration" of the placenta away from the internal os by the differential growth rates of upper and lower uterine segments. (05 Mar 2000) |
| total placenta previa | Placenta previa in which the placenta entirely covers the internal os of the cervix. Synonym: central placenta previa, total placenta previa. (05 Mar 2000) |
| vasa previa | The umbilical cord vessels come before the foetal head during delivery. (12 Dec 1998) |
| accessory placenta | An extra placenta separate from the main placenta. Also called a succenturiate or supernumerary placenta. (12 Dec 1998) |
| adherent placenta | A placenta that fails to separate cleanly from the uterus after delivery. (05 Mar 2000) |
| annular placenta | A placenta in the form of a band encircling the interior of the uterus. Synonym: zonary placenta. (05 Mar 2000) |
| battledore placenta | A placenta in which the umbilical cord is attached at the border; so-called because of the fancied resemblance to the racquet (racket) used in battledore, a precursor to badminton. (05 Mar 2000) |
| bidiscoidal placenta | A placenta with two separate disc-shaped portions attached to opposite walls of the uterus, normal for certain monkeys and shrews, and occasionally found in humans. (05 Mar 2000) |
| margination of placenta | See: placenta marginata. (05 Mar 2000) |
| maternal placenta | <anatomy> The part of the placenta derived from the uterine tissue. See: placenta. Synonym: maternal placenta, placenta uterina. (05 Mar 2000) |
| villous placenta | A placenta in which the chorion forms villi. (05 Mar 2000) |
| retained placenta | Incomplete separation of the placenta and its failure to be expelled at the usual time after delivery of the child. Synonym: incarcerated placenta. (05 Mar 2000) |
| chorioallantoic placenta | A placenta (such as that of primates) in which the chorion is formed by the fusion of the allantoic mesoderm and vessels to the inner face of the serosa. (05 Mar 2000) |
| chorioamnionic placenta | A form of placentation in which the amnion is fused to the inside of the chorion, thus permitting interchange of water and electrolytes between mother and foetus. (05 Mar 2000) |