Coagulation and fibrinolysis in pregnancies complicated by fetal growth retardation

Placental bed research: I. The placental bed: from spiral arteries remodeling to the great obstetrical syndromes

The term placental bed was coined to describe the maternal-fetal interface (ie, the area in which the placenta attaches itself to the uterus). Appropriate vascularization of this area is of vital importance for the development of the fetus; this is why systematic investigations of this area have now been carried out. Initially, the challenge was the identification and classification of the various successive branching of uterine arteries in this area. These vessels have a unique importance because failure of their physiological transformation is considered to be the anatomical basis for reduced perfusion to the intervillous space in women with preeclampsia, fetal growth restriction, preterm labor, preterm premature rupture of membranes, abruptio placentae, and fetal death. To investigate in depth the pathophysiology of the placental bed, some 60 years ago, a large number of placental bed biopsies, as well as of cesarean hysterectomy specimens with placenta in situ, from both early and late normotensive and hypertensive pregnancies, were carefully dissected and analyzed. Thanks to the presence of a series of specific physiological changes, characterized by the invasion and substitution of the arterial intima by trophoblast, this material allowed the identification in the placental bed of normal pregnancies of the main vessels, the uteroplacental arteries. It was then discovered that preeclampsia is associated with defective or absent transformation of the myometrial segment of the uteroplacental arteries. In addition, in severe hypertensive disease, atherosclerotic lesions were also found in the defective myometrial segment. Finally, in the basal decidua, a unique vascular lesion, coined acute atherosis, was also identified This disorder of deep placentation, coined defective deep placentation, has been associated with the great obstetrical syndromes, grouping together preeclampsia, intrauterine growth restriction, preterm labor, preterm premature rupture of membranes, late spontaneous abortion, and abruptio placentae. More recently, simplified techniques of tissue sampling have been also introduced: decidual suction allows to obtain a large number of decidual arteries, although their origin in the placental bed cannot be determined. Biopsies parallel to the surface of the basal plate have been more interesting, making possible to identify the vessels' region (central, paracentral, or peripheral) of origin in the placental bed and providing decidual material for immunohistochemical studies. Finally, histochemical and electron microscopy investigations have now clarified the pathology and pathogenetic mechanisms underlying the impairment of the physiological vascular changes.

Measurement of euglobulin fibrinolysis time in women with retarded fetal development. The effect of the clamping and step tests on plasminogen activator activity

The effects of two experimental stimuli, clamping of the cubital vein and exercise (step test), on the euglobulin lysis time of women with retarded fetal development (92 cases), with physiologic pregnancy (50 cases) and non-pregnant women (20 cases) were studied. Both tests resulted in a pronounced shortening of euglobulin lysis time in the non-pregnant and to a lesser extent in the physiologic pregnancy cases (statistically significant after clamping of the cubital vein, statistically insignificant after the step test). In the etiologically heterogeneous group of pregnancy with retarded fetal development the response to both stimuli was weaker in comparison with the normal pregnancy group, and in many cases (58.7%) even "paradoxical", that is, instead of a rise in fibrinolytic activity, a fall was observed. These results indicate that in women with retarded fetal development fibrinolytic activity of the blood doses not rise as readily as it does in normal pregnancies. This applies both to local response (clamping test) and systemic response (step test), and is probably due to a fall in the plasminogen activator content of the venous vessel walls. As a working hypothesis, it is presumed that insufficiency of the plasminogen activator activity system facilitates the accumulation of fibrin deposits in the uterine--placental blood circulation, and contributes to retardation of intrauterine fetal growth.

Soluble fibrinogen--fibrin complexes in intrauterine growth retardation

Soluble fibrinogen--fibrin complex levels were found to be significantly higher in plasma samples from pregnant women with babies suffering from intrauterine growth retardation, when compared with levels found in normal pregnancy. As soluble fibrinogen--fibrin complexes are formed following activation of the coagulation pathway in vitro and in vivo these findings may reflect the increased local intravascular coagulation within the placenta demonstrated histologically in pregnancies complicated by growth retardation. The use of more sensitive methods for detecting alterations in coagulation, fibrinolysis and platelet function may prove useful in the diagnosis of intrauterine growth retardation antenatally.