Clinics in obstetrics and gynaecology最新文献

This review presents basic aspects of placental morphology with particular reference to the regional specialization of human placental tissues. Intrauterine visualization of the placenta is now possible with new non-invasive methods. Echotomographic ultrasound images of the placenta in vivo and in vitro are of the greatest value for clinical and pathological diagnosis. X-ray computed tomography, though it cannot be applied to pregnant women, is invaluable for the study of circulatory and pathologic changes in the placenta isolated post partum. Nuclear magnetic resonance imaging is another useful adjunct not only for placental localization but also to detect changes of placental morphology with an accuracy almost as good as ultrasonography. Fourier-transform spectroscopy now offers a unique opportunity to obtain computed biochemical data on the metabolic evolution of the human placenta.

The placenta has a considerable functional reserve capacity, easily repairs ischaemic damage, is able to compensate for toxic injury and does not appear to age. Most of the macroscopically visible abnormalities of the placenta are of no functional significance, the major exception to this general banality being the uncommon large haemangioma which can cause complications in the mother, fetus and neonate. Most of the histological abnormalities seen in the placental villi represent a reaction to alterations in either maternal or fetal blood flow through the placenta, but a failure of adequate maturation of the villous tree may impair the functional efficiency of the placenta, as may defective trophoblastic differentiation. Infections of the placenta are important but do not influence placental function, whilst there is currently no firm evidence that the placenta ever suffers immune-mediated damage. Intrinsic placental 'insufficiency' is extremely rare and it is becoming increasingly clear that this clinical syndrome is usually due to a restricted supply of maternal oxygen and nutrients as a result of inadequate transformation of the spiral arteries into uteroplacental vessels. This failure of placentation represents an abnormality of the relationship between fetal and maternal tissues at a relatively early stage of pregnancy, and it is only by gaining a better understanding of this relationship that the problems posed by such conditions as pre-eclampsia and idiopathic intrauterine growth retardation will be answered.

Many placental proteins appear in the serum and tumours of patients with malignant disease, but few have achieved an established position in clinical management. Chorionic gonadotrophin is a sensitive and effective marker for trophoblastic disease. Gonadal germ cell tumours containing extraembryonic structures can secrete hCG and SPl, which both may provide unique clinical information about recurrent disease. Placental proteins belonging to the PP series are an interesting new group which has added to our knowledge of the biology of tumours. However, none of them has yet proven to be important in clinical practice. Placental alkaline phosphatase isoenzymes are secreted by seminomas and dysgerminomas, and, in some clinics, they are routinely examined for monitoring treatment of these tumours. Whereas the clinical usefulness of the above markers is well established for the monitoring of treatment and early detection of recurrent disease, none of them can be used for the screening of cancer in an apparently healthy population.