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Pregnancy Complications

Glossary of Terms

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abruption/abruptio placentae: separation of all or part of the placenta from the uterine wall prior to delivery of the fetus. Often secondary to a retroplacental hemorrhage due to abnormal uteroplacental vessels. A sudden detachment can cause fetal demise

accessory placental lobe: sufficient oxygen and nutrients allow villous proliferation in areas that should normally undergo physiologic atrophy, requiring velamentous vessels. Predisposing factors include anatomic abnormalities of the uterus that might constrain normal expansion of the fundus or implantation in the lower uterine segment

accreta: disorder, characterized by abnormally deep invasion, in which all or part of the villi are in direct contact with the myometrium and are anchored to muscle fibers rather than decidua (see percreta and increta)

acute ascending infection: an ascending organism colonizes the extraplacental membranes or crosses the membranes (intact or ruptured) into the amniotic fluid

acute atherosis: characterized by the presence of fibrinoid necrosis accompanied by lipid-laden macrophages and a perivascular mononuclear cell infiltrate

amnion: the avascular inner "shell" of the conceptus, embryologically continuous with the epithelium of the umbilical cord and the fetal skin. It forms the transparent membranous sac that is filled with amniotic fluid

amnion bands: a result of amniotic membrane rupture, bands of the membrane can wrap around parts of the fetus and lead to structural malformations or amputations

aneuploidy: chromosome number is not a multiple of the normal haploid (23), usually caused by random erros in meiosis or mitosis

anoxia: suffocation; total lack of oxygen and concomittent rise of carbon dioxide in the fetal blood. Requires complete failure of maternal perfusion (e.g., secondary to complete abruption), complete failure of placental oxygen uptake or complete failure of oxygen transfer from the placenta to the fetus (e.g., secondary to complete occlusion of the umbilical cord)

asphyxia: a condition of impaired gas exchange which leads, if persistant, to hypoxemia and hypercapnia; process is identified by fetal acidosis (as measured in umbilical arterial blood), which reflects the degree of anaerobic metabolism required during periods of hypoxia or increased oxygen demand


basal plate: the 'floor' of the intervillous space where fetal and maternal tissues intermingle and where, at term, a natural cleavage plane for placental separation is found

blighted ovum: early pregnancy loss marked histologically by hydropic degenerative change in villi, uniform villous edema and lack of trophoblastic hyperplasia


chemical pregnancy: form of miscarriage. It is termed "chemical" because the only clinical evidence of pregnancy is a lab test, which indicates that that implantation occurred but only developed long enough to raise your circulating blood level of hCG. These are often early non-viable genetic "accidents."

chorioamnionitis: migration of polymorphonuclear leukocytes (maternal inflammatory cells) which develops when bacteria or mycoplasms gain access to the extraplacental membranes and progress along the surface of the chorion, sometimes gaining access to the amniotic fluid. The route of infection may be transcervical (ascending), transabdominal, or hematogenous (from the maternal bloodstream)

chorangioma (placental hemangioma): nontrophoblastic tumor characterized by abnormal vascular development within the placental parenchyma

choriocarcinoma: a malignant neoplasm of trophoblastic cells, formed by abnormal proliferation without the production of chorionic villi

chorion: the outer "shell" of the conceptus. Originally a sphere, out-pouching of the chorion form the primitive chorionic villi (the fetal part of the placenta)

chorionicity: monochorionic siblings develop within the same chorion and are obligatory monozygous (identical) siblings. Dichorionic siblings develop within their own chorion (80% fraternal, 20% identical). Identical twins can be dichorionic if the splitting of the conceptus occurs prior to the formation of the chorion (usually before implantation)

chorionic villi: the bulk of the placental disc is composed of chorionic villi. The villi reflect progressive extension of the chorionic villous tree, beginning with main fetal stems branching off the chorionic plate early in pregnancy. Branching and formation of new chorionic villi continues in many placentas until term, and fetal nutrient exchange occurs at their interface with the intervillous space

chorionic plate: the base from which the placental villous trees are suspended toward the maternal blood supply into the intervillous space, originally covered by syncytiotrophoblast which is replaced by fibrinoid

chronic hypertension: sustained hypertension (elevated blood pressure) identified either prior to conception or before 20 weeks gestation, or if the elevation persists for more than 6 weeks after delivery

chronic villitis: chronic inflammatory infiltrate of the placental villi composed of plasma cells, lymphocytes and histiocytes or macrophages

conceptus: a term used to describe the total "package" of the placenta and its membranes and the little one growing inside the placental sac.

cotyledon: the placenta is divided into 15-20 by septa (invaginations of maternal decidua), but are not thought to represent discrete functional placental units


decidua: gestational endometrium

dispermy: fertilization of the ovum by two sperm cells

dysmenorrhea: painful menstruation

dysplasia: altertion in size, shape and organization of cells


eclampsia: pre-eclampsia accompanied by grand-mal seizures before, during or after labor

ectopic: the implantation of a fertilized ovum outside the uterine cavity, most often within the fallopian tubes. It can be life threatening and although its cause is poorly understood, its association with other forms of reproductive failure suggest a common etiology

edema: an abnormal accumulation of fluid in intercellular spaces of the body

endometriosis: a progressive disease characterized by the presence of endometrial tissue (the lining of the uterus) outside of the uterine cavity. Found more frequently in infertile women

endometrium: mucous membrane lining the uterus


fetal growth restriction: low observed birthweight to expected birthweight ratio (based upon gestational age)

fibrinoid necrosis: an acellular mass of dense eosinophilic material on the trophoblast basement membrane

fundus: section of the uterus where the spiral artery density, and thus oxygen/nutrient availability, is greatest. It is the preferential area for placental implantation

funisitis: presence of polymorphonuclear leukocytes in the umbilical cord. Represents fetal inflammatory response to intraamniotic infection


gestational diabetes: characterized by the onset or recognition of impaired glucose tolerance during pregnancy and its resolution following delivery


HELLP syndrome: hemolysis, elevated liver enzymes, and low platelet count

histopathology: the correlation of function with the gross and microscopic structure of cells and tissue

homocysteine: a sulfhydryl-containing amino acid derivative that normally undergoes rapid enzymatic metabolism and is thus present at only low levels in plasma. Plasma concentration is influenced by levels of folic acid, vitamin B12 and vitamin B6 in the diet, the total methionine (an amino acid) content of dietary intake, presence of certain genetic polymorphisms (CBS, MTHFR, MS), age and gender.

hydatiform mole: the most common form of trophoblastic disease. Complete mole is characterized by 46 paternally derived chromosomes (no maternal contribution), trophoblastic hyperplasia, edematous villi and the absence of fetal tissue. Partial mole is charaterized by 69 chromosomes (one maternal set supplemented by two paternal sets), focal edematous villi admixed with normal villi, trophoblastic hyperplasia and the presence of fetal tissues. Invasive moles (rarely seen in partial moles) are characterized by villi that invade the myometrium

hypertension: persistently elevated blood pressure, may be primary or secondary (associated with another disease)

hypotension: persistently depressed blood pressure

hypoxia: an environment of low oxygen availability, exposure to which may result in either an adaptive fetal response (e.g., shunting of blood to the brain) or fetal compromise (secondary to decompensation). Severe and/or prolonged exposure results in irreversible neural damage


idiopathic: occurring without known cause

increta: disorder, characterized by abnormally deep invasion, in which all or part of the villi directly invade the myometrium (see percreta and accreta)

infarct: an area of ischemic villous necrosis, usually secondary to blockage of one or more spiral arteries. Small infarcts, especially located marginally, are considered normal.

insulin resistance: an impaired biological response to either exogenous or endogenous

intervillous space: anatomical space filled by maternal blood provided by the uteroplacental arteries. Fetal nutrient exchange occurs at the interface between the intervillous space and the chorionic villi


karyotype: the chromosomal constitution of the cell nucleus; also refers to the photomicrograph display of chromosomes


lesion: any pathologic area of tissue damage

lipoprotein(a): lipoprotein composed of LDL cholesterol and apolipoprotein A thought to reduce vascular fibrinolytic capacity and thromboresistance, and be a marker of accelerated atherosclerosis

luteal phase defect: characterized by endometrial histology (on endometrial biopsy) that is repeatedly out of phase by more than two days, associated with recurrent pregnancy loss


maternal floor infarct: lesion initiated by fibrin in the decidua and adjacent villi (misnamed since it does not include the ischemic necrosis characteristic of infarct). Villi are progressively engulfed, rendering the villi atrophic and often resulting in uteroplacental insuffciency

meconium: the bile stained contents of the fetal intestine. Meconium discharge prior to birth (resulting in the presence of meconium in the amniotic fluid and staining of the fetus or placenta) may be a consequence of fetal stress and hypoxia. Problems can occur if the meconium fluid is aspirated by the fetus

mosaicism: the presence in an individual of two or more cell lines that are karyotypically or genotypically distinct and are derived from a single zygote

myometrium: the tunica muscularis (muscle layer) of the uterus


neutrophil: a granular leukocyte

nondisjunction: failure of two homologous chromosomes to pass to separate cells during the first division of meiosis, or the two chromatids to pass to separate cells during the second meiotic division. As a result, one daughter cell has two chromosomes or chromotids while the other has none


oligohydramnios: decreased amniotic fluid volume


percreta: disorder of the placenta characterized by abnormally deep invasion in which all or part of the villi penetrate the entire thickness of the uterine wall, resulting in uterine rupture (see increta and accreta)

perivillous fibrin deposition: characterized by an eosinophilic fibrin coating on the surface of villi

placenta previa: low implantation of the placenta covering the cervical os

polycystic ovary syndrome (PCO): syndrome often characterized clinically by irregular menses, elevated circulating androgens, insulin resistance, obesity, hirsutism and in many cases anovulation and infertility. The ovaries are typically enlarged with white glossy capsules beneath which are multiple cysts in various developmental stages

polyhydramnios: elevated amniotic fluid volume

polyploidy: chromosomes exist in a multiple of the normal diploid number (e.g., triploidy, tetraploidy)

preeclampsia: a toxemia of pregnancy, characterized by hypertension, edema and proteinuria

products of conception (POC): material recovered from a first trimester spontaneous pregnancy loss or D & C, generally a mixture of fetal and placental tissue

premature rupture of membranes (PROM): rupture of the extraembryonic membranes more than one hour before the onset of labor


Robertsonian translocation: abnormality in which individual chromosomes are fused at the centromere


spiral artery: named for their 'corkscrew' appearance, these blood vessels of the endometrium are converted during pregnancy to become the uteroplacental arteries that connect the maternal uterine arteries to the intervillous space

stroma: the supporting tissue or matrix of an organ

syncytiotrophoblast (villous): multinucleated trophoblastic continuous cell surface of the arborized placental villi, which functions as the maternal fetal transport barrier


teratogen: toxic environmental agents that have been associated with fetal malformations/birth defects (drugs, chemicals, irradiation)

thrombocytopenia: abnormal maternal blood condition characterized by reduced platelet concentrations in the plasma, caused by either decreased platelet production/survival or increased consumption

thrombophilia: a state, either inherited or acquired, characterized by impaired natural anticoagulant or fibrinolytic pathways and a damaged vascular endothelium, and resulting in the abnormal formation of venous or arterial thrombosis. Status can be exacerbated by the existence of more than one predisposing factor (e.g. factor V Leiden mutation and MTHFR heterozygosity)

thrombosis: abnormal clotting, either venous or arterial

trisomy: existence of an extra (third) copy of a chromosome (e.g., Trisomy 13, 16, 18, 21 and 22)

trophoblast: placental epithelial cells, can be either nonvillous (interstitial or endovascular) or villous

twin-twin transfusion syndrome: occurs when there is an unbalanced shunting of blood, see the general description link above for more information



UPI uterine artery pulsitility index: a measure of resistance to blood flow in the arteries (blood vessels) of your uterus. Normally the placenta adapts the blood vessels so that uterine artery flow is less pulsatile and more continuous, so a low pulsatility index is good. This is a specialized form of transvaginal ultrasound.

umbilical artery: in normal pregnancies there are two. The arteries, along with the umbilical vein, are surrounded by the connective tissue of the cord (Wharton's jelly) which protects the vessels from the mechanical trauma associated with cord torsion and normal fetal movement. A single uterine artery, resulting from either agenesis or atrophy of the second artery, may be less hemodynamically efficient and has been anecdotally associated with fetal growth restriction

umbilical knot: true tight knots in the cord can cause fetal demise or compromise, false knots are varicosities of the umbilical vein and are not generally associated with compromise

umbilical vein: delivers umbilical venous blood from the placental capillary bed to the fetus (there is only one vein). See umbilical artery above for more information.

uteroplacental arteries: end result of endovascular trophoblastic disruption of the musculoelastic elements of the spiral arteries of the decidua and myometrium. This allows progressive distension and accomodation of increasing blood flow as fetal demands increse (see 'vascular conversion')


vascular conversion (physiologic change) of spiral arteries: characterized by replacement of the original musclo-elastic tunica media by mononuclear trophoblast embedded in fibrinoid. A necessary step in the development of the high capacitance/low resistance vascular system required as pregnancy progresses. Absence of this change has been extensively documented in preeclampsia

vasculosyncytial membrane (VSM): in third trimester terminal villi, the fusion of fetal capillaries and the thin overlying syncytiotrophoblast to form an area believed to be important in gas exchange

velamentous insertion of the umbilical cord: insertion of cord on the extraplacental membranes. These cord vessels may be more susceptible to mechanical compression as they are no longer protected by the connective tissue (Wharton's jelly) of the umbilical cord proper


zygosity: in the case of twins, refers to whether they develop from one zygote (monozygosity) or two (dizygosity)

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