Syncytiotrophoblastic fragments in first-trimester decidual veins: evidence of placental perfusion by the maternal circulation early in pregnancy

Human Extravillous Trophoblasts Penetrate Decidual Veins and Lymphatics before Remodeling Spiral Arteries during Early Pregnancy

In humans, the defective invasion of the maternal endometrium by fetal extravillous trophoblasts (EVTs) can lead to insufficient perfusion of the placenta, resulting in pregnancy complications that can put both mother and baby at risk. To study the invasion of maternal endometrium between (W)5.5–12 weeks of gestation by EVTs, we combined fluorescence in situ hybridization, immunofluorescence and immunohistochemistry to determine the presence of (male) EVTs in the vasculature of the maternal decidua. We observed that interstitial mononuclear EVTs directly entered decidual veins and lymphatics from W5.5. This invasion of decidual veins and lymphatics occurred long before endovascular EVTs remodelled decidual spiral arteries. This unexpected early entrance of interstitial mononuclear EVTs in the maternal circulation does not seem to contribute to the materno-placental vascular connection directly, but rather to establish (and expand) the materno-fetal interface through an alternative vascular route.

Extravillous trophoblasts invade more than uterine arteries: evidence for the invasion of uterine veins

During the first trimester of pregnancy, extravillous trophoblasts (EVTs) invade into the decidual interstitium to the first third of the myometrium, thereby anchoring the placenta to the uterus. They also follow the endovascular and endoglandular route of invasion; plug, line and remodel spiral arteries, thus being responsible for the establishment of hemotrophic nutrition with the beginning of the second trimester and invade and open uterine glands toward the intervillous space for a histiotrophic nutrition during the first trimester. The aim of this study was to provide proof that uterine veins are invaded by EVTs similar to uterine arteries and glands in first trimester of pregnancy. Therefore, serial sections from in situ first trimester placenta were immuno-single- and immuno-double-stained to distinguish in a first step between arteries and veins and secondly between invaded and non-invaded vessels. Subsequently, invasion of EVTs into uterine vessels was quantified. Our data show that uterine veins are significantly more invaded by EVTs than uterine arteries (29.2 ± 15.7 %) during early pregnancy. Counted vessel cross sections revealed significantly higher EVT invasion into veins (59.5 ± 7.9 %) compared to arteries (29.2 ± 15.7 %). In the lumen of veins, single EVTs were repeatedly found, beside detached glandular epithelial cells or syncytial fragments. This study allows the expansion of our hitherto postulated concept of EVT invasion during first trimester of pregnancy. We suggest that invasion of EVTs into uterine veins is responsible the draining of waste and blood plasma from the intervillous space during the first trimester of pregnancy.

Aspirin and low-molecular weight heparin combination therapy effectively prevents recurrent miscarriage in hyperhomocysteinemic women

The management of recurrent pregnancy loss (RPL) still remains a great challenge, and women with polycystic ovarian syndrome (PCOS) are at a greater risk for spontaneous abortion. Treatment with low-molecular-weight heparin (LMWH) has become an accepted treatment option for women with RPL; however, the subgroup of women, who are likely to respond to LMWH, has not been precisely identified. The present study evaluated the efficacy of LMWH with reference to PCOS and associated metabolic phenotypes including hyperhomocysteinemia (HHcy), insulin resistance (IR) and obesity. This prospective observational study was conducted at Institute of Reproductive Medicine, Kolkata, India. A total of 967 women with history of 2 or more consecutive first trimester abortions were screened and 336 were selected for the study. The selected patients were initially divided on the basis of presence or absence of PCOS, while subsequent stratification was based on HHcy, IR and/or obesity. The subjects had treatment with aspirin during one conception cycle and aspirin-LMWH combined anticoagulant therapy for the immediate next conception cycle, if the first treated cycle was unsuccessful. Pregnancy salvage was the sole outcome measure. The overall rate of pregnancy salvage following aspirin therapy was 43.15%, which was mostly represented by normohomocysteinemic women, while the salvage rate was lower in the HHcy populations irrespective of the presence or absence of PCOS, IR, or obesity. By contrast, aspirin-LMWH combined therapy could rescue 66.84% pregnancies in the aspirin-failed cases. Logistic regression analyses showed that HHcy remained a significant factor in predicting salvage rates in the PCOS, IR, and obese subpopulations controlled for other confounding factors. With regard to pregnancy salvage, combined anticoagulant therapy with aspirin and LMWH conferred added benefit to those with HHcy phenotype.

Intervillous and uteroplacental circulation in normal early pregnancy and early pregnancy loss assessed by 3-dimensional power Doppler angiography

OBJECTIVE

To assess intervillous and uteroplacental circulation in early normal pregnancies and miscarriages.

STUDY DESIGN

One hundred normal pregnancies and 46 delayed miscarriages were evaluated by 3-dimensional vaginal ultrasound and power Doppler angiography. Volumes of the early placenta and the subplacental area were obtained between 5 and 12.6 weeks' gestation. The placental volume, vascularization index, flow index, and vascularization flow index was calculated.

RESULTS

Intraclass correlation coefficients ranged from 0.961 for placental volume to 0.885 for intervillous flow index. Intervillous power Doppler signals were not detected before the sixth week. Placental volume (R(2) = 0.68), intervillous vascularization index (R(2) = 0.30), flow index (R(2) = 0.33) and vascularization flow index (R(2) = 0.35), uteroplacental flow index (R(2) = 0.34), and vascularization flow index (R(2) = 0.17) increase significantly (P < .001) throughout the first trimester of normal pregnancies. Uteroplacental vascularization index was not significantly related to gestational age. Intervillous vasculariztion index, flow index, and vascularization flow index were significantly raised in miscarriages, but there were no significant differences for uteroplacental vascularization index, flow index, or vascularization flow index.

CONCLUSION

Intervillous and uteroplacental blood flow increases throughout the first trimester of normal pregnancies. Intervillous circulation is abnormally increased when a miscarriage is diagnosed.

First-trimester Doppler investigation of the uterine circulation

There is now strong evidence that fetal events can significantly impact postnatal health and disease development. Doppler velocimetry can identify some early pathologic changes in pregnancy. Many investigators have tried to delineate the normal and pathologic models of the uterine circulation in the first trimester, but much has yet to be defined. A discrete amount of confusion derives from the incomplete knowledge of the initial placental development, and particularly the development of the intervillous circulation. This article comprehensively reviews the literature on first-trimester Doppler in both normal and complicated pregnancies, and briefly discusses potential future areas of application.

Maternal serum soluble fms-like tyrosine kinase 1 concentrations are not increased in early pregnancy and decrease more slowly postpartum in women who develop preeclampsia

OBJECTIVE

We measured maternal serum soluble fms-like tyrosine kinase 1 concentrations across pregnancy and immediately postpartum in women who developed preeclampsia and normal pregnant women.

STUDY DESIGN

This was a nested case control study of 113 normal pregnant women and 55 women with preeclampsia.

RESULTS

Serum soluble fms-like tyrosine kinase 1 concentrations increased similarly in early pregnancy in both groups. Mean serum soluble fms-like tyrosine kinase 1 concentrations were increased in women who developed preeclampsia, compared with normal pregnant women, and this increase was most pronounced in severe preeclampsia. However, many women with preeclampsia had soluble fms-like tyrosine kinase 1 concentrations similar to normal pregnant women. Lastly, soluble fms-like tyrosine kinase 1 decreased rapidly after delivery, but this decrease was significantly slower in women with severe preeclampsia.

CONCLUSION

Increased soluble fms-like tyrosine kinase 1 is not an early-pregnancy event among women who later develop preeclampsia. Increased soluble fms-like tyrosine kinase 1 is more likely to be present in women with severe preeclampsia, but it is not present in all women with preeclampsia. Soluble fms-like tyrosine kinase 1 concentrations decrease more slowly after delivery in women with preeclampsia, consistent with a decreased rate of excretion or continued production.

Trophoblastic oxidative stress in relation to temporal and regional differences in maternal placental blood flow in normal and abnormal early pregnancies

Onset of the maternal-placental circulation was studied by Doppler ultrasonography in 65 pairs of age-matched normal and abnormal pregnancies. In normal pregnancies intervillous blood flow increased with gestational age, being detected in 9 of 25 cases at 8 to 9 weeks but in 18 of 20 at 12 to 13 weeks (P = 0.001). By contrast, in abnormal pregnancies flow was detected in nearly all cases (22 of 25) at 8 to 9 weeks (P < 0.001). In addition, regional differences were observed between the groups. Early flow was restricted to the peripheral regions of most normal placentas (P < 0.001), whereas in missed miscarriages it was most common in central regions or throughout the placenta (P < 0.05 and P < 0.001, respectively). Immunoreactivity for heat shock protein 70 and nitrotyrosine residues was greater in samples from peripheral than from central regions of normal placentas (P = 0.028 and P = 0.019, respectively), and from missed miscarriages compared to controls (P = 0.005 and P = 0.001, respectively). Our results indicate that oxidative damage to the trophoblast, induced by premature and widespread onset of the maternal placental circulation secondary to shallow trophoblast invasion, is a key factor in early pregnancy loss. High oxygen concentrations in the periphery of normal early placentas may similarly induce local regression of the villi, leading to formation of the chorion laeve.

Comparison of ultrasonographic and Doppler mapping of the intervillous circulation in normal and abnormal early pregnancies

OBJECTIVE

To assess the value of ultrasonography and Doppler imaging in characterizing the intervillous circulation in normal and abnormal early pregnancy.

DESIGN

Cross-sectional study.

SETTING

Tertiary care academic hospital.

PATIENT(S)

Eighty-five normal pregnancies and 125 missed miscarriages at 7 to 13 weeks of gestation.

INTERVENTION(S)

Grey-scale ultrasonography was used to evaluate the placental anatomy and detect moving echoes inside the intervillous space, and color power Doppler imaging was used to detect continuous venous-like flow in the placental tissue.

MAIN OUTCOME MEASURE(S)

Degree of agreement between two investigators for use of grey-scale imaging, comparison of detection of moving echoes in normal and abnormal pregnancies, and comparison of detection of intervillous circulation with grey-scale and color Doppler imaging in abnormal pregnancies.

RESULT(S)

The overall degree of agreement between the two investigators was good. A significantly different distribution of blood flow was found between normal and abnormal pregnancies at 7 to 9 weeks and 10 to 11 weeks but not at 12 to 13 weeks. Intervillous moving echoes were detected by grey-scale imaging significantly more frequently than an intervillous blood flow was detected with color Doppler imaging.

CONCLUSION(S)

In early pregnancy failure, there is a premature and diffuse onset of intervillous blood flow that can be detected by grey-scale imaging. This abnormal blood flow pattern may increase the oxidative stress on the early placental tissue and subsequently impair placental development.

Placental basal plate formation is associated with fibrin deposition in decidual veins at sites of trophoblast cell invasion

OBJECTIVE

We hypothesize that placenta growth and basal plate (Nitabuch's fibrinoid) formation involves fibrin deposition in decidual veins as trophoblast cells invade.

STUDY DESIGN

Decidua from women who underwent first trimester elective pregnancy termination (n = 15 women), in situ pregnancy (n = 2 women), and ectopic pregnancy (n = 5 women) were immunostained with polyclonal antibodies to fibrin. Serial sections of decidua were studied with monoclonal antibodies to oncofetal fibronectin, cytokeratin, and Factor VIII-related antigen.

RESULTS

In all intrauterine pregnancies, trophoblast cells were identified with clots in decidual veins. Fibrin and oncofetal fibronectin were present in veins at sites of trophoblast cell invasion and in the developing basal plate matrix where villi had implanted into veins. Fibrin deposits were not seen in decidual parietalis of ectopic or in situ pregnancies.

CONCLUSION

We have identified fibrin in decidual veins that is associated with trophoblast cell invasion. We speculate that the formation of basal plate protein (Nitabuch's fibrinoid) involves these intravenous fibrin deposits.

Comparative developmental anatomy of the murine and human definitive placentae

The placenta of eutherian mammals is a remarkable biological structure. It is composed of both zygote-derived and maternal cells, and mediates the complex interactions between the mother and the fetus that are necessary for fetal growth and survival. While the genetic basis of human placental development and function is largely unknown, its understanding is of immense clinical importance because placentopathies of unknown genetic aetiology are thought to be the cause of many types of pregnancy complications including unexplained miscarriage and intrauterine growth retardation. The mouse is the best-studied mammalian experimental genetic model system and research is not restricted by the inherent ethical and practical limitations associated with the human. As a result, knowledge about the genetic control of mouse placental development has expanded greatly in recent years. In order for this to be of benefit to medical practice, extrapolations from murine to human placentation have to be made. However, comprehensive comparisons of the placentae of these two species are rare. This review therefore compares the developmental anatomy of the placenta between humans and mice with emphasis on structures and cell types that might be analogous between the two species. This could be of particular benefit to mouse developmental geneticists who study placental development and have an interest in the possible clinical implications of their work.

Lateral placental growth occurs by trophoblast cell invasion of decidual veins

During human pregnancy, growth of the placenta is proportionally greater than the growth of the decidual surface, suggesting that trophoblast cells invade the decidua at the placenta's margin. We hypothesized that a method of lateral placental growth was trophoblast cell invasion of decidual veins. This was investigated in two in situ pregnancies and in tissues from 100 women undergoing elective termination at 8-12 weeks of gestation. Decidua was compared to normal secretory endometrium. Histological sections were stained by immunohistochemistry to identify trophoblast cell and vascular antigens, as well as vascular cell adhesion molecule (VCAM), integrin subunits beta(1)and beta(4), and oncofetal fibronectin. Dilated veins were observed in all decidua but not in the secretory endometrium. Decidual and myometrial veins contained villi, trophoblast cell islands and syncytial elements. Decidual endothelial cells expressed vascular cell adhesion molecule (VCAM). Villous trophoblast cells were integrin subunits beta(4)positive and beta(1)negative. Trophoblast cell islands in the placenta and within decidual veins were integrin subunits beta(1)positive and beta(4)negative. Trophoblast cell islands and villi attached to veins, and mononuclear cells, invaded decidual stroma. Oncofetal fibronectin was present at sites of trophoblast invasion. These findings suggest that a method of lateral placental growth is trophoblast cell invasion of veins.