OVERVIEW

Finally! A concise yet complete, easy-to-use reference guide designed to be used everyday in the delivery room and in the Surgical Pathology gross room, by everyone charged with gross placental examination. Obstetricians, general practitioners, pathologists, residents, nurse-midwives, Labor and Delivery nurses, OB nurses, nurse practitioners, physician assistants and pathologists' assistants will benefit from its content. Its unique clinical-pathological correlation approach allows quick review of the possible placental findings associated with specific maternal and fetal conditions, and the fetal and neonatal consequences thereof, a focus which is also helpful for those providing prenatal care.

Section I. Clinicopathological Correlations is the "driving force" of the guide. It is divided into chapters based upon the Maternal Indications, Fetal Indications and Placental Indications for placental examination. Each indication is subsequently described by its Definition, Clinical Associations, Gross Features, Microscopic Features, Etiology and Significance. For clarification of features of the normal and abnormal placenta, turn to Section II. Placental Pathology. For an explanation of terminology used in prenatal clinical histories, turn to Section III. Clinical Definitions. In recent years, the placenta has played an increasingly important role in cases of birth injury litigation. To review the placenta's impact on litigation, turn to Section IV. Legal Implications.

Additionally, there are over 70 commonly used Abbreviations, 23 clinical and pathological Tables and 41 Figures - photomicrographs, schematics, and illustrations. The user friendly Table of Contents and Index provide quick and easy access to desired information, cross referenced through out all sections of the guide.

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For example, a 38 year old, Gravida 2 Para 1, Fullterm 0, Preterm 1, Abortion 0, Living 1 woman presents in active labor at 36 weeks gestation. Her maternal risk includes 20 year history of smoking 1 pack of cigarettes per day. Her pregnancy history includes third trimester bleeding. Fetal history includes IUGR. Delivery is by cesarean section due to partial placenta previa. Placental examination reveals low placental weight, retroplacental hematoma/abruptio placentae and numerous infarcts.

To review causes of third trimester bleeding, turn to Section III. Clinical Definitions, Chapter 13 Clinical Definitions: Hemorrhage, Third Trimester, page 129:

"Is an ominous complication of pregnancy, although bleeding in late pregnancy is not uncommon. 10-15% of cases require medial attention. Third trimester bleeding is a major cause of maternal death, and perinatal morbidity and mortality. Most serious bleeding (2-3% of pregnancies, 30% of third trimester hemorrhage) is due to abruptio placentae or placenta previa. Other less common causes include: 1) circumvallate placenta (more commonly a major cause of 2nd trimester hemorrhage and fetal death); 2) abnormal blood clotting mechanisms; 3) uterine rupture. Most blood loss due to placental accidents is maternal; fetal blood loss is possible, particularly with placental laceration. Bleeding from ruptured vasa previa is the only cause of pure fetal hemorrhage."

Want more information about abruptio placentae? Turn to Section II: Placental Pathology, Chapter 9 Maternal Surface (Basal Plate): Abruptio Placentae, page 81:

"In cases of abruptio placentae, a clinical condition in which the placenta separates from the uterine wall before delivery (placental abruption), the basal plate should be inspected for blood clot. In very acute abruption (25-50% of cases) there may be no grossly appreciable abnormality. Adherent, sometimes laminated blood clot, occasionally dissecting into the adjacent parenchyma, may be seen with a recent abruption. The clot of an older abruption is firm, dry and stringy, and eventually brown. The placental tissue overlying and adjacent to the adherent blood clot may be: a) dark red due to villous hemorrhage - an early abruption; b) thinned out, over a "saucer-like" depression; or c) depressed, firm and pale with a several day old infarct."

Want more information about infarcts? Turn to Section Ii: Placental Pathology, Chapter 10: Parenchyma, page 89:

"A placental infarct results from localized interruption of the maternal blood supply, resulting in regional collapse of the intervillous space and crowding, touching of neighboring villi. Grossly, infarcts are firm due to the crowded villi. They may be dark red-brown or yellow-white depending upon their age and intervillous space blood content. Acute infarcts are grossly firm and microscopically show villous congestion. Older infarcts are grossly yellow-white and microscopically demonstrate progressive loss of nuclear staining, initially of the trophoblast and finally of the entire villus with fibrin deposition in the intervillous space. Keep in mind true organization of the infarct never occurs!

Compared to other "fibrous nodules," infarcts are generally granular due to their villous content and are usually based on the maternal surface. Marginal infarcts seen in otherwise normal term placentas are common and have no significance for the mother or fetus. Small infarcts in term placentas are not uncommon and may be "normal."

However, any infarct in a premature placenta is abnormal. Large infarcts, even at term, greater than 3 cm and especially if centrally located, are definitely abnormal. Such infarcts are associated with serious perinatal morbidity and mortality. Depending upon the maternal vascular condition (hypertension, pre-eclampsia), extensive placental infarct involving 10-50% of the parenchyma may result in fetal death.

It is important to estimate and record the total amount of infarcted placental parenchyma. It is ultimately important and may have medicolegal implications in growth retarded infants."

How does the patient's smoking history affect all this? Turn to Section I: Clinicopathological Correlation, Chapter 2 Maternal Indications: Smoking, page 33:

"Definition. Tobacco is the dried prepared leaves of the plant Nicotiana tabacum, and the source of various alkaloids, the principal one being nicotine.

Clinical Associations. The older the woman the greater the risk; increased risk for antepartum hemorrhage secondary to abruptio placentae or placenta previa, premature rupture of membranes and preterm labor.

Gross Features. May see abruptio placentae, circumvallate placenta, thin umbilical cord, single umbilical artery, chorioamnionitis as a consequence of premature rupture of membranes, fetal stem vessel lesions, changes associated with placenta previa and large infarcts.

Microscopic Features. May also see fetal stem vessel lesions, marginal decidual necrosis, parenchymal and vascular changes of ischemia, increased basal lamina thickness beneath the trophoblastic covering of the villi, decreased density of terminal villi blood vessels and "cobblestone" appearance of the umbilical artery endothelial cells with leakage of plasma and red blood cells into the endothelial spaces.

Etiology. Smoking causes decreased prostacyclin and increased thromboxane synthesis (which alters fetal and maternal circulations toward vasoconstriction), increased platelet aggregation and decreased blood flow. Necrosis of the decidua at the placental margin, due to vascular changes inhibiting blood flow, and microinfarcts are sometimes the nidus for placental abruptions.

Significance. Smoking a single cigarette reduces uteroplacental blood flow for 5-15 minutes, which may be long enough to produce decidual necrosis and small placental infarcts, putting the fetus at risk for premature delivery or death. The increased thickness of the basement membrane and decreased density of terminal villi blood vessels, may impose a barrier to the placental-fetal passage of nutrients and oxygen. This may explain why infants of cigarette smokers often have lower birth weights and higher hemoglobin levels at birth than infants of nonsmokers. Although smokers have a lower incidence of hypertension and pre-eclampsia before and during pregnancy, the fetus is at greater risk for threatened or late spontaneous abortion, diminished breathing movements and increase perinatal mortality. Smoking increases the risk for placenta previa; it correlates with the number of years a woman has smoked and not with smoking during pregnancy. Because smoking accelerates the sclerotic narrowing of small uterine arteries and arterioles, blood flow to many parts of the endometrium is reduced. Later, when the blastocyst is "looking" for a place to implant, these affected areas of endometrium appear less hospitable, therefore the blastocyst implants low in the uterus, where the placenta may cover the cervical os.