Prognostic value of placental ultrasound in pregnancies complicated by absent end-diastolic flow velocity in the umbilical arteries

Cord coiling, umbilical cord insertion and placental shape in an unselected cohort delivering at term: relationship with common obstetric outcomes

BACKGROUND

The position of the placental cord insertion, its shape and cord coiling are thought to be associated with perinatal outcome. This study derives indices describing the relationship of cord insertion to the placental centre, the shape of the placenta and cord coiling in placentas from unselected term pregnancies. Further, we investigate these indices in pregnancies affected by pre-eclampsia (PET), pregnancy induced hypertension (PIH), gestational diabetes mellitus (GDM) and delivery of a small for gestational age (SGA) baby.

DESIGN/METHODOLOGY

Eight hundred and sixty one unselected women with singleton pregnancy delivering at 37-42 weeks were prospectively recruited to this study. Placental axes and their relationship with the cord insertion were measured using digital photography and proprietary software. From these, the cord centrality (distance of umbilical cord insertion from the centre) and placental eccentricity (deviation of the placental shape from circular) were derived. The cord coiling index (number of coils in the cord divided by the length of cord in cm) was also calculated from manual measurements.

RESULTS

The mean value of cord centrality index was 0.36 (SD = 0.21) and of placental eccentricity 0.49 (SD = 0.17). Left direction of umbilical cord coiling was more common than right (79% vs 16.4%) The mean cord coiling index was 0.20 (SD = 0.09) coils/cm. The indices were constant between 37 and 42 weeks and were no different in the non-affected population compared to women with pre-eclampsia (n = 17), PIH, (n = 27), GDM (n = 38) or delivery of an SGA baby (n = 54).

CONCLUSION

The cord centrality index that we derive suggests that the cord insertion is most commonly 'off centre', and eccentricity index that the placental shape is elliptical. Therefore, contrary to widely held belief, the cord does not normally insert centrally nor is the placenta normally round in shape. There is a preponderance of left sided coiling. There was no difference for any of the indices between the non-affected pregnancies and pregnancies affected by pre-eclampsia, PIH, GDM and SGA.

HEPARIN IN HUMAN PLACENTAL DEVELOPMENT AND THE PREVENTION OF PLACENTAL COMPLICATIONS OF PREGNANCY

The development of effective anticoagulant drugs available for use in pregnancy has resulted in dramatic improvements for a number of potentially life-threatening conditions. These include the treatment and prevention of venous thromboembolism and the thrombotic complications of antiphospholipid antibody syndrome, as well as the management of pregnant women with mechanical heart valves. The most commonly used class of drug includes heparin, a highly-charged macro-molecule that does not cross the placenta, in contrast to the potentially teratogenic and fetotoxic oral drug warfarin. This review will focus on our current lack of understanding of the wider actions of heparin and examines the possibility that large numbers of pregnant women are presently being treated inappropriately with heparin.

First-trimester assessment of placenta function and the prediction of preeclampsia and intrauterine growth restriction

Preeclampsia and intrauterine growth restriction (IUGR) are major contributors to perinatal mortality and morbidity worldwide. Both are characterized by impaired trophoblastic invasion of the maternal spiral arteries and their conversion from narrow muscular vessels to wide non-muscular channels. Despite improvement in the understanding of the pathophysiology of these conditions, ability to accurately identify pregnant woman who will develop them is limited. This greatly impairs the development and testing of preventive interventions. While different measures of placental dysfunction have been associated with increased risk for adverse pregnancy outcomes, the ability of any single one to accurately predict these outcomes is poor. Developing predictive tests is further challenged by difficulty in the timing of the measurements, as both the structural and biochemical characteristics of the placenta change with increasing gestational age. The ideal screening test would accurately predict the development of adverse pregnancy outcomes early enough to provide a window for preventive interventions. Improvement in ultrasound technology provides potentially useful novel tools for evaluating placental structure, but measurements need to be standardized in order to be useful. Maternal serum analyte screening is a noninvasive test of placental biochemical function, but present serum marker alone is not sufficiently accurate to suggest its routine use in clinical practice. The use of first trimester biochemical markers in combination with uterine artery Doppler screening is promising as a potential screening tool. Prospective longitudinal studies using standardized methodology are necessary to further evaluate the choice of parameters and strategies of combination to achieve the best predictive models.

Antithrombotic therapy for improving maternal or infant health outcomes in women considered at risk of placental dysfunction

BACKGROUND

Pregnancy complications such as pre-eclampsia and eclampsia, intrauterine growth restriction and placental abruption are thought to have a common origin related to abnormalities in the development and function of the placenta.

OBJECTIVES

To compare, using the best available evidence, the benefits and harms of antenatal antithrombotic therapy to improve maternal or infant health outcomes in women considered at risk of placental dysfunction, when compared with other treatments, placebo or no treatment.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2010).

SELECTION CRITERIA

Randomised controlled trials comparing antenatal antithrombotic therapy (either alone or in combination with other agents) with placebo or no treatment, or any other treatment in the antenatal period to improve maternal or infant health outcomes in women considered at risk of placental dysfunction.

DATA COLLECTION AND ANALYSIS

Two review authors evaluated trials under consideration for appropriateness for inclusion and methodological quality without consideration of their results according to the prestated eligibility criteria. We used a fixed-effect meta-analysis for combining study data if the trials were judged to be sufficiently similar. We investigated heterogeneity by calculating I(2) statistic, and if this indicated a high level of heterogeneity among the trials included we used a random-effects model.

MAIN RESULTS

Our search strategy identified 14 reports of 10 studies for consideration, of which five met the inclusion criteria, involving 484 women. Four studies compared heparin (alone or in combination with dipyridamole) with no treatment; and one compared trapidil (triazolopyrimidine). While there were no statistically significant differences identified for the primary outcomes following heparin treatment, it was associated with a reduction in the risk of pre-eclampsia, eclampsia, and infant birthweight less than the 10th centile for gestational age.

AUTHORS' CONCLUSIONS

The review identified no significant differences for the primary outcomes perinatal mortality, preterm birth less than 34 weeks' gestation, and childhood neurodevelopmental handicap, although the number of studies and participants was small. While treatment with heparin appears promising with a reduction in pre-eclampsia, eclampsia, and infant birthweight less than the 10th centile for gestational age, the number of studies and participants included was small, and to date important information about serious adverse infant and long-term childhood outcomes is unavailable. Further research is required.

Chronic maternal hypertension characterized by renal dysfunction is associated with reduced placental blood flow during late gestation in rabbits

Maternal hypertension associated with renal disease is a common pregnancy complication. Previously, we have shown in a rabbit model of mild hypertension that offspring from hypertensive mothers have increased blood pressure as adults. In human pregnancy, hypertension has been associated with decreased utero-placental blood flow. The aim of this study was to determine placental blood flow (PBF) in mild (2-kidney-1-wrapped; 2K-1W) and moderate (2-kidney-2-wrapped; 2K-2W) rabbit models of maternal hypertension. We hypothesized that PBF would be inversely related to the severity of the hypertension. PBF and renal blood flow (RBF) were measured using microspheres on day 28 of a 32-day gestation, in normotensive (sham), 2K-1W, and 2K-2W hypertensive groups. Mean arterial pressure (MAP, ∼7 mmHg, P < 0.05) was increased, and RBF (∼35%, P < 0.05) was reduced in the 2K-1W and 2K-2W (MAP ∼20 mmHg, P < 0.01; RBF ∼53%, P < 0.05) groups compared with the sham group. In the 2K-1W group, PBF fell by ∼12% ( P = 0.08) and fetal-to-placental weight ratio increased by ∼12% ( P < 0.01) compared with the sham group, reflecting an increase in the functional capacity of the placenta to deliver nutrients to the fetus. In the 2K-2W group, PBF decreased ∼51% ( P < 0.05) compared with the sham group, without changes in placental efficiency. Thus, in late gestation, placental blood flow was significantly reduced in the moderate hypertension group, without accompanying changes in fetal or placental weight or placental efficiency. In contrast, mild hypertension resulted in an increase in placental efficiency, without significant changes in placental blood flow. These findings suggest that mild and moderate hypertension may alter placental delivery of nutrients via differing mechanisms dependent upon the severity of the hypertension.

Umbilical artery Doppler indices in small for gestational age fetuses: correlation with adverse outcomes and placental abnormalities

OBJECTIVE

The purpose of this study was to compare the screening efficiency of the umbilical artery systolic to diastolic ratio (S/D), pulsatility index (PI), and absent end-diastolic flow (AEDF) for adverse pregnancy outcomes and placental abnormalities in small for gestational age (SGA) fetuses.

METHODS

We conducted a retrospective cohort study of Doppler examinations of 161 nonanomalous SGA fetuses. The reliability of the S/D and PI were quantified by intraclass correlation coefficients. The association of the S/D, PI, and AEDF with adverse outcomes and placental abnormalities was compared by the chi(2) test.

RESULTS

There was a simple association of Doppler results with adverse outcomes, which was mitigated when controlled for gestational age. For all measures of adverse outcomes, the specificity of abnormal Doppler results exceeded the sensitivity, and the negative predictive value was greater than the positive predictive value. Comparing the S/D with the PI, there was no significant difference in the sensitivity; however, the specificity of the PI was at least 90% and exceeded that of the S/D for all outcomes. The intraclass correlation coefficients of the S/D and PI were similar, indicating no difference in reliability. Placental abnormalities were significantly more common in cases with abnormal Doppler values (positive predictive value, 94%) with no overlap in the types of placental lesions in most cases.

CONCLUSIONS

As an initial screen for adverse outcomes in SGA fetuses, the umbilical artery Doppler S/D, PI, and AEDF were imprecise. However, these measures were all strongly and similarly predictive of placental abnormalities, especially lesions of maternal underperfusion and fetal vascular obstruction.

Beyond oxygen: complex regulation and activity of hypoxia inducible factors in pregnancy

In the first trimester the extravillous cytotrophoblast cells occlude the uterine spiral arterioles creating a low oxygen environment early in pregnancy, which is essential for pregnancy success. Paradoxically, shallow trophoblast invasion and defective vascular remodelling of the uterine spiral arteries in the first trimester may result in impaired placental perfusion and chronic placental ischemia and hypoxia later in gestation leading to adverse pregnancy outcomes. The hypoxia inducible factors (HIFs) are key mediators of the response to low oxygen. We aimed to elucidate mechanisms of regulation of HIFs and the role these may play in the control of placental differentiation, growth and function in both normal and pathological pregnancies. The Pubmed database was consulted for identification of the most relevant published articles. Search terms used were oxygen, placenta, trophoblast, pregnancy, HIF and hypoxia. The HIFs are able to function throughout all aspects of normal and abnormal placental differentiation, growth and function; during the first trimester (physiologically low oxygen), during mid-late gestation (where there is adequate supply of blood and oxygen to the placenta) and in pathological pregnancies complicated by placental hypoxia/ischemia. During normal pregnancy HIFs may respond to complex alterations in oxygen, hormones, cytokines and growth factors to regulate placental invasion, differentiation, transport and vascularization. In the ever-changing environment created during pregnancy, the HIFs appear to act as key mediators of placental development and function and thereby are likely to be important contributors to both normal and adverse pregnancy outcomes.

Placental size and the prediction of severe early-onset intrauterine growth restriction in women with low pregnancy-associated plasma protein-A

OBJECTIVES

Screening studies for trisomy 21 demonstrate that low maternal serum pregnancy-associated plasma protein-A (PAPP-A) at 11-13 weeks' gestation is associated with stillbirth, intrauterine growth restriction (IUGR) and pre-eclampsia in chromosomally normal fetuses. However, the strength of these associations is too weak to justify screening for these placental insufficiency syndromes. Our objective was to evaluate placental size and uterine artery (UtA) Doppler imaging as second-stage screening tests for women with low PAPP-A.

METHODS

We prospectively studied 90 normal singleton pregnancies with first-trimester PAPP-A </= 0.30 multiples of the median. Maternal serum alpha-fetoprotein (AFP) at 15-18 weeks' gestation, and second-trimester placental size and UtA Doppler indices were assessed as predictors of pregnancy outcome.

RESULTS

The risks of IUGR, preterm delivery before 32 weeks' gestation and stillbirth were significantly associated with small placental size (relative risk (RR), 3.96; 95% CI, 2.21-5.98; RR, 3.96; 95% CI, 2.21-5.98; and RR, 6.44, 95% CI, 2.74-14.54, respectively) and elevated AFP (RR, 3.67; 95% CI, 1.78-7.71; RR, 2.48; 95% CI, 1.23-4.94; and RR, 5.14; 95% CI, 1.66-16.85, respectively), but not with abnormal UtA Doppler indices. The combination of elevated AFP and small placental size further increased the risk of IUGR (RR, 4.88; 95% CI, 2.88-5.31), delivery before 32 weeks' gestation (RR, 4.25; 95% CI, 2.38-4.98) and stillbirth (RR, 7.44; 95% CI, 3.04-3.75).

CONCLUSIONS

Small placental size and elevated AFP, but not UtA Doppler indices, identify women with low PAPP-A at high risk of IUGR, extreme preterm delivery and stillbirth. These additional screening tests may directly improve perinatal outcomes in women with low PAPP-A.

Reducing stillbirths: screening and monitoring during pregnancy and labour

BACKGROUND

Screening and monitoring in pregnancy are strategies used by healthcare providers to identify high-risk pregnancies so that they can provide more targeted and appropriate treatment and follow-up care, and to monitor fetal well-being in both low- and high-risk pregnancies. The use of many of these techniques is controversial and their ability to detect fetal compromise often unknown. Theoretically, appropriate management of maternal and fetal risk factors and complications that are detected in pregnancy and labour could prevent a large proportion of the world's 3.2 million estimated annual stillbirths, as well as minimise maternal and neonatal morbidity and mortality.

METHODS

The fourth in a series of papers assessing the evidence base for prevention of stillbirths, this paper reviews available published evidence for the impact of 14 screening and monitoring interventions in pregnancy on stillbirth, including identification and management of high-risk pregnancies, advanced monitoring techniques, and monitoring of labour. Using broad and specific strategies to search PubMed and the Cochrane Library, we identified 221 relevant reviews and studies testing screening and monitoring interventions during the antenatal and intrapartum periods and reporting stillbirth or perinatal mortality as an outcome.

RESULTS

We found a dearth of rigorous evidence of direct impact of any of these screening procedures and interventions on stillbirth incidence. Observational studies testing some interventions, including fetal movement monitoring and Doppler monitoring, showed some evidence of impact on stillbirths in selected high-risk populations, but require larger rigourous trials to confirm impact. Other interventions, such as amniotic fluid assessment for oligohydramnios, appear predictive of stillbirth risk, but studies are lacking which assess the impact on perinatal mortality of subsequent intervention based on test findings. Few rigorous studies of cardiotocography have reported stillbirth outcomes, but steep declines in stillbirth rates have been observed in high-income settings such as the U.S., where cardiotocography is used in conjunction with Caesarean section for fetal distress.

CONCLUSION

There are numerous research gaps and large, adequately controlled trials are still needed for most of the interventions we considered. The impact of monitoring interventions on stillbirth relies on use of effective and timely intervention should problems be detected. Numerous studies indicated that positive tests were associated with increased perinatal mortality, but while some tests had good sensitivity in detecting distress, false-positive rates were high for most tests, and questions remain about optimal timing, frequency, and implications of testing. Few studies included assessments of impact of subsequent intervention needed before recommending particular monitoring strategies as a means to decrease stillbirth incidence. In high-income countries such as the US, observational evidence suggests that widespread use of cardiotocography with Caesarean section for fetal distress has led to significant declines in stillbirth rates. Efforts to increase availability of Caesarean section in low-/middle-income countries should be coupled with intrapartum monitoring technologies where resources and provider skills permit.

Rheological and physiological consequences of conversion of the maternal spiral arteries for uteroplacental blood flow during human pregnancy

Physiological conversion of the maternal spiral arteries is key to a successful human pregnancy. It involves loss of smooth muscle and the elastic lamina from the vessel wall as far as the inner third of the myometrium, and is associated with a 5–10-fold dilation at the vessel mouth. Failure of conversion accompanies common complications of pregnancy, such as early-onset preeclampsia and fetal growth restriction. Here, we model the effects of terminal dilation on inflow of blood into the placental intervillous space at term, using dimensions in the literature derived from three-dimensional reconstructions. We observe that dilation slows the rate of flow from 2 to 3 m/s in the non-dilated part of an artery of 0.4–0.5 mm diameter to approximately 10 cm/s at the 2.5 mm diameter mouth, depending on the exact radius and viscosity. This rate predicts a transit time through the intervillous space of approximately 25 s, which matches observed times closely. The model shows that in the absence of conversion blood will enter the intervillous space as a turbulent jet at rates of 1–2 m/s. We speculate that the high momentum will damage villous architecture, rupturing anchoring villi and creating echogenic cystic lesions as evidenced by ultrasound. The retention of smooth muscle will also increase the risk of spontaneous vasoconstriction and ischaemia–reperfusion injury, generating oxidative stress. Dilation has a surprisingly modest impact on total blood flow, and so we suggest the placental pathology associated with deficient conversion is dominated by rheological consequences rather than chronic hypoxia.

Glial cell missing-1 transcription factor is required for the differentiation of the human trophoblast

Mammalian placentation is a highly regulated process and is dependent on the proper development of specific trophoblast cell lineages. The two major types of trophoblast, villous and extravillous, show mitotic arrest during differentiation. In mice, the transcription factor, glial cell missing-1 (Gcm1), blocks mitosis and is required for syncytiotrophoblast formation and morphogenesis of the labyrinth, the murine equivalent of the villous placenta. The human homolog GCM1 has an analogous expression pattern, but its function is presently unknown. We studied GCM1 function in the human-derived BeWo choriocarcinoma cell line and in first trimester human placental villous and extravillous explants. The GCM1 expression was either inhibited by siRNA and antisense oligonucleotides methods or upregulated by forskolin treatment. Inhibition of GCM1 resulted in an increased rate of proliferation, but prevented de novo syncytiotrophoblast formation in syncytially denuded floating villous explants. GCM1 inhibition prevented extravillous differentiation along the invasive pathway in extravillous explants on matrigel. By contrast, forskolin-induced expression of GCM1 reduced the rate of proliferation and increased the rate of syncytialization in the floating villous explant model. Our studies show that GCM1 has a distinct role in the maintenance, development and turnover of the human trophoblast. Alterations in GCM1 expression or regulation may explain several aspects of two divergent severe placental insufficiency syndromes, namely preeclampsia and intrauterine growth restriction, which cause extreme preterm birth.

Determinants of adverse perinatal outcome in high-risk women with abnormal uterine artery Doppler images

OBJECTIVE

The purpose of this study was to evaluate the prognostic role of placental ultrasound imaging at 19-23 weeks of gestation in clinically high-risk women with abnormal uterine artery Doppler (UTAD).

STUDY DESIGN

Placentas of 60 women with abnormal UTAD were examined at 19-23 weeks of gestation for shape and texture abnormalities. Findings were correlated with clinical outcomes (preterm delivery at <32 weeks of gestation; birth weight <10th percentile [small for gestational age]; preeclampsia/hemolysis, elevated liver enzymes, low platelets; early-onset intrauterine growth restriction with abnormal umbilical artery Doppler; and intrauterine fetal death) and maternal serum screening data. Placental disease was reviewed by 2 perinatal pathologists.

RESULTS

Women with abnormal placental shape at 19-23 weeks of gestation (n = 28) had higher odds of intrauterine fetal death (odds ratio, 4.5; 95% CI, 1.3-15.6), delivery at <32 weeks of gestation (odds ratio, 4.7; 95% CI, 1.6-14.1]), and intrauterine growth restriction (odds ratio, 4.7; 95% CI, 1.4-15.1]) than did the women with a normal placental shape. Thirty-two of 41 placentas (74%) weighed <10th percentile, and 36 of 43 placentas (83%) had ischemic-thrombotic pathologic condition. There was no association between abnormal placental shape at 19-23 weeks of gestation and placental weight, but 5 of 6 placentas that were <10 cm long were <10th percentile for weight at delivery. There was a poor correlation between measures of ultrasound texture at 19-23 weeks of gestation and the presence of specific lesions at delivery.

CONCLUSION

Combined abnormal UTAD and placental dysmorphologic condition before fetal viability identifies a subset of women who are at risk of adverse outcomes. Placental size is critical in the determination of the outcome in this situation because of the very high prevalence of destructive lesions, although present methods of placental imaging have significant limitations.

Stillbirth

In the UK, about one in 200 infants is stillborn, and rates of stillbirth have recently slightly increased. This recent rise might reflect increasing frequency of some important maternal risk factors for stillbirth, including nulliparity, advanced age, and obesity. Most stillbirths are related to placental dysfunction, which in many women is evident from the first half of pregnancy and is associated with fetal growth restriction. There is no effective screening test that has clearly shown a reduction in stillbirth rates in the general population. However, assessments of novel screening methods have generally failed to distinguish between effective identification of high-risk women and successful intervention for such women. Future research into stillbirth will probably focus on understanding the pathophysiology of impaired placentation to establish screening tests for stillbirth, and assessment of interventions to prevent stillbirth in women who screen positive.

Severe early onset pre-eclampsia: prognostic value of ultrasound and Doppler assessment

OBJECTIVE

Assess the prognostic value of ultrasound and Doppler parameters in severe preterm pre-eclampsia.

STUDY DESIGN

Prospective cohort study in Cape Town, South Africa, involving 113 women with severe pre-eclampsia between 24 and 34 weeks of gestation and managed expectantly when suitable. Serial ultrasound and multivessel Doppler assessments were performed 2 to 3 times weekly. Observations included fetal weight estimation, growth pattern, amniotic fluid volume, appearance of the heart and bowel, pulsatility index of the uterine, umbilical and middle cerebral arteries and ductus venosus. Perinatal outcome (death or neurological compromise, n=12) and major morbidity (n=62) were related to findings at recruitment and on the last assessment preceding delivery.

RESULTS

In univariate analysis, fetal growth asymmetry and waveform analysis of all three fetal vessels significantly correlated with both end points. The initial fetal weight estimation with a cutoff weight of 1080 g had the highest sensitivity (83.3%) and negative predictive value (97.5%) for poor outcome (P<0.001) while the final ductus venosus pulsatility index had the highest specificity (92%) and positive predictive value (33%). The combination of a raised placentocerebral ratio and ductus venosus pulsatility index close to delivery had the highest (57.1%) positive predictive value. Logistic regression showed the best overall predictive model for poor outcome to be a combination of initial fetal weight estimation and final ductus venosus pulsatility index (overall accuracy 94.6%, RR 20.20 (7.36, 55.41)). The initial fetal weight estimation with a cutoff weight of 1283 g provided the best correct prediction of major morbidity (83.2% overall accuracy, sensitivity 79.0%, specificity 88.2%, positive and negative predictive values of 89.1 and 77.6% respectively). This was better than using the gestational age at recruitment or delivery, birth weight or any of the Doppler results. The prediction of morbidity was not improved by the addition of any other variable in logistic regression analysis.

CONCLUSION

For the short-term outcome measures assessed in this study, the estimated fetal weight at the time of diagnosis is the most important prognostic factor in severe pre-eclampsia with some additional value of ductus venosus assessment.

Usefulness of a placental profile in high-risk pregnancies

OBJECTIVE

Test the hypothesis that a placental function profile can reassure most high-risk women with normal test results yet accurately can identify a subset of women who are destined for major complications that will be attributable to placental disease.

STUDY DESIGN

This was a prospective study of 212 high-risk pregnancies that used the placental profile (16- to 18-week maternal serum screening, 18- to 23-week uterine artery Doppler imaging, and placental morphologic condition). Odds ratios (95% CI) were derived for intrauterine fetal death (IUFD), preterm delivery at < 34 weeks of gestation, preeclampsia/hemolysis, elevated liver enzymes, and low platelet count syndrome (HELLP) syndrome, small for gestational age delivery, and early-onset intrauterine growth restriction (IUGR); all normal test results (n =125) were compared with > or = 1 abnormal test results.

RESULTS

The odds of the development of adverse outcomes were significantly less in women with all normal test results (preeclampsia/HELLP [odds ratio, 0.2; 95% CI, 0.1-0.4]), preterm delivery (odds ratio, 0.1; 95% CI, 0.06-0.3), small for gestational age delivery (odds ratio, 0.2; 95% CI, 0.09-0.3), early-onset IUGR (0), and IUFD (odds ratio, 0.05 [0.01-0.2]). Combining those women with two (n = 21) of 3 (n = 15) abnormal test results together predicted 14 of 19 severe IUGR and 15 of 22 IUFD cases.

CONCLUSION

This placental function profile at 16-23 weeks of gestation can reassure women with normal test results by identifying a smaller subset of women who are at reduced risk of perinatal morbidity or death from severe IUGR.

Developmental changes in hemodynamics of uterine artery, utero- and umbilicoplacental, and vitelline circulations in mouse throughout gestation

In human pregnancy, abnormal placental hemodynamics likely contribute to the etiology of early-onset preeclampsia and fetal intrauterine growth restriction. The mouse is increasingly being deployed to study normal and abnormal mammalian placental development, yet the placental hemodynamics in normal pregnancy in mice is currently unknown. We used ultrasound biomicroscopy to noninvasively image and record Doppler blood velocity waveforms from the maternal and embryonic placental circulations in mice throughout gestation. In the uterine artery, peak systolic velocity (PSV) increased significantly from 23 ± 2 (SE) to 59 ± 3 cm/s, and end-diastolic velocity (EDV) increased from 7 ± 1 to 28 ± 2 cm/s in nonpregnant versus full-term females so that the uterine arterial resistance index (RI) decreased from 0.70 ± 0.02 to 0.53 ± 0.02. Velocities in the maternal arterial canal in the placenta were low and nearly steady and increased from 0.9 ± 0.03 cm/s at embryonic day 10.5 (E10.5) to 2.4 ± 0.07 cm/s at E18.5. PSV in the umbilical artery increased steadily from 0.8 ± 0.1 cm/s at E8.5 to 15 ± 0.6 cm/s at E18.5, whereas PSV in the vitelline artery increased from 0.6 ± 0.1 cm/s at E8.5 to 4 ± 0.2 cm/s at E13.5 and then remained stable to term. In the umbilical artery, the EDV detection rate was 0% at ≤E14.5 and 94% at E18.5, and the RI decreased from 1 to 0.82 ± 0.01 during this interval. We conclude that ultrasound biomicroscopy can be used to monitor placental hemodynamics during pregnancy in mice. These results provide novel information concerning the development of the vitelline and placental circulations in mice and reveal strong similarities in placental hemodynamics between mice and humans.

Apoptosis and its role in the trophoblast

During early placentation the trophoblast of the human placenta differentiates to the villous and extravillous types of trophoblast. Villous trophoblast provides the epithelial cover of the placental villous trees in direct contact to maternal blood. Extravillous trophoblast invades maternal uterine tissues thus directly contacting maternal stromal and immune cells. A subset of extravillous trophoblast, endovascular trophoblast initially occludes the lumen of spiral arteries and comes into direct contact with maternal blood. In recent years apoptosis has been described in both types of trophoblast and the importance of this cascade for the normal function of the trophoblast has become obvious. One feature of serious conditions such as preeclampsia or intrauterine growth restriction is changes in apoptosis regulation in villous and/or extravillous trophoblast resulting in altered trophoblast invasion and/or shedding into the maternal circulation. This review summarizes recent findings on trophoblast apoptosis in normal and pathologic pregnancies.

Ultrasound detection of placental insufficiency in women with 'unexplained' abnormal maternal serum screening results

Serious placental insufficiency results in perinatal death or preterm birth from ischemic-thrombotic pathology, a process which has its origins in placental maldevelopment in the first trimester. A proportion of at-risk pregnancies may be identified from abnormalities in first or second trimester serum screening data, uterine artery Doppler waveforms or placental shape and texture at the time of the 18-20-week anatomical examination. In combination, these tests may be capable of recognizing a subset of at-risk pregnancies with 50% positive predictive values. Early recognition before fetal viability affords opportunities to direct women to regional perinatal care centres for enhanced maternal-fetal surveillance, corticosteroids to enhance fetal lung maturation, prophylactic measures to prevent pre-eclampsia and optimal decision making around the time of delivery. The creation of regional screening programs to use screening data with a placental focus is likely to be cost-effective, because existing patterns of care are utilized. More importantly, this strategy can direct women to participate in clinical research programs designed to reduce morbidity and mortality from this common group of conditions.

Increased expression of sFlt-1 in in vivo and in vitro models of human placental hypoxia is mediated by HIF-1

Elevated expression of soluble vascular endothelial growth factor receptor-1 (sFlt-1) in preeclampsia plays a major role in the pathogenesis of this serious disorder of human pregnancy. Although reduced placental oxygenation is thought to be involved in the pathogenesis of preeclampsia, it is unclear how oxygen regulates placental sFlt-1 expression. The aims herein were to investigate sFlt-1 expression in in vivo and in vitro physiological and pathological models of human placental hypoxia and to understand the role of hypoxia inducible factor-1 (HIF-1) in regulating the expression of this molecule. sFlt-1 expression in placental villi was significantly increased under physiological low oxygen conditions in early first-trimester and in high-altitude placentae, as well as in pathological low oxygen conditions, such as preeclampsia. In high-altitude and in preeclamptic tissue, sFlt-1 localized within villi to perivascular regions, the syncytiotrophoblast layer, and syncytial knots. In first-trimester villous explants, low oxygen, but not hypoxia-reoxygenation (HR), increased sFlt-1 expression. Moreover, exposure of villous explants to dimethyloxalyl-glycin, a pharmacological inhibitor of prolyl-hydroxylases, which mimics hypoxia by increasing HIF-1alpha stability, increased sFlt-1 expression. Conversely, HIF-1alpha knockdown using antisense oligonucleotides, decreased sFlt-1 expression. In conclusion, placental sFlt-1 expression is increased by both physiologically and pathologically low levels of oxygen. This oxygen-induced effect is mediated via the transcription factor HIF-1. Low oxygen levels, as opposed to intermittent oxygen tension (HR) changes, play an important role in regulating sFlt-1 expression in the developing human placenta and hence may contribute to the development of preeclampsia.

Second-trimester prediction of severe placental complications in women with combined elevations in alpha-fetoprotein and human chorionic gonadotrophin

OBJECTIVE

The purpose of this study was to determine the ability of uterine artery Doppler and placental ultrasound to identify adverse clinical outcomes attributable to severe placental dysfunction in women with second-trimester unexplained elevated maternal serum screening of alpha-fetoprotein and human chorionic gonadotropin.

STUDY DESIGN

Fifty singleton pregnancies with elevated alpha-fetoprotein (3.5 multiples of median [range 2.1 to 10.5]) and human chorionic gonadotropin (5.3 multiples of median [range 2.5 to 21.7]) and a normal fetal anatomical ultrasound were prospectively evaluated with placental ultrasound and uterine artery Doppler at referral between 19 and 23 weeks' gestation.

RESULTS

Abnormalities in both placental ultrasound and uterine artery Doppler (n = 24) predicted preterm delivery less than 32 weeks from any cause (n = 24) (75% sensitivity, 75% positive predictive value; likelihood ratio positive 3.3 [1.6 to 6.8]), intrauterine fetal death (n = 12) (100% sensitivity, 50% positive predictive value; likelihood ratio positive 3.1 [2.0 to 5.0]), and intrauterine growth restriction with absent/reversed end-diastolic flow (n = 17) (sensitivity 94%, positive predictive value 67%, likelihood ratio positive 3.9 [2.0 to 6.2]) . Ischemic-thrombotic pathology was present in 88% of placentas examined (n = 32).

CONCLUSION

Uterine artery Doppler and placental morphology identified most pregnancies with combined abnormal maternal serum screening destined to result in extremely premature delivery and/or perinatal death. Abnormal maternal serum screening reports could include a recommendation for placental ultrasound testing when no fetal explanation has been identified.

Divergent trophoblast invasion and apoptosis in placental bed spiral arteries from pregnancies complicated by maternal anemia and early-onset preeclampsia/intrauterine growth restriction

OBJECTIVE

Impaired trophoblast invasion into spiral arteries is associated with early-onset intrauterine growth restriction and preeclampsia. We compared trophoblast invasion into spiral arteries in pregnancies with maternal anemia or early-onset preeclampsia/intrauterine growth restriction and related these findings to trophoblast apoptosis.

STUDY DESIGN

Full-thickness uterine wall samples were obtained from women with early-onset preeclampsia/intrauterine growth restriction (n = 6), normal pregnancies (n = 5), and chronic anemia (n = 8). Trophoblast invasion into the walls of spiral arteries was quantified by morphometric analysis of paraffin sections stained with anticytokeratin 18, antiactin, and anticytokeratin 18 neoepitope (M30) antibodies.

RESULTS

Trophoblast invasion into spiral arteries was increased in anemic pregnancies (mean [SD]: 206 [46] cell profiles/mm2) and severely impaired in preeclamptic/intrauterine growth restriction pregnancies (17 [6]), compared with normal subjects (149 [52]). Spiral artery lumen area was increased in anemia (0.07 [0.03] mm2) versus normal pregnancies (0.09 [0.04] mm2) and reduced in preeclampsia/intrauterine growth restriction (0.04 [0.02] mm2). Trophoblast apoptosis was similar in anemic (4.2% [3.4%]) and normal (5.0% [1.9%]) pregnancies but increased in preeclampsia/intrauterine growth restriction (12% [5.6%]).

CONCLUSION

Trophoblast invasion into the placental bed in early-onset preeclampsia/intrauterine growth restriction is limited by increased apoptosis, resulting in narrower spiral arteries, which is in contrast to findings in anemia.

Vascular biology in implantation and placentation

Pregnancy leads to dramatic changes of the vascular system of the mother and enables the development of a completely new vascular system within the growing embryo including the formation of the placenta as the exchange organ between both circulations. Besides a general adaptation of the maternal blood system, the uterine spiral arteries display the greatest changes. Within placental villi angiogenesis as well as vasculogenesis can be found already a few weeks after implantation. Both systems in parallel will determine the blood flow within the placental villi and the intervillous space. Finally, compromised blood flow on either side of the placental membrane will not only lead to fetal malnutrition, but will also trigger morphological changes of the villous trees. This review tries to cover all the above-mentioned topics and will try to depict the consequences of poor placentation on mother and fetus.

Fetal response to maternal exercise in pregnancies with uteroplacental insufficiency

OBJECTIVE

The purpose of this study was to determine the fetal response to submaximal maternal exercise at 22 to 26 weeks in pregnancies with abnormal uterine artery Doppler.

STUDY DESIGN

This was a prospective comparison of singleton pregnancies with uteroplacental vascular insufficiency (UPVI) (mean uterine pulsatility index [PI] values >1.45 [n = 12]) and those with normal uterine artery Doppler (n = 23). Maternal and fetal cardiovascular responses to 5 minutes of steady state cycling at 10% and at 15% of predicted work rate maximum were studied.

RESULTS

Umbilical artery Doppler deteriorated after exercise in patients with UPVI (pre PI 1.4 [0.35-2.14], post PI 1.64 [0.45-2.18]). Three (25%) had transient absent-end diastolic flow (AEDF) in umbilical artery, 2 of which developed early-onset intrauterine growth restriction (IUGR) with AEDF. Fetal cardiac output studies remained stable during the examinations.

CONCLUSION

Submaximal steady state exercise had a transient deleterious effect in a subset of women with uteroplacental vascular insufficiency destined to develop early-onset IUGR.

A Puzzling Intrauterine Death: Non-Compaction of the Fetal Ventricular Myocardium Presenting With Reversed End-Diastolic Flow Velocity in the Umbilical Arteries

BACKGROUND

Absent or reversed end-diastolic flow velocity (ARED) in the umbilical arteries is typically associated with severe intrauterine growth restriction (IUGR), although there may be other causes, such as aneuploidy.

CASE

A healthy 30-year-old gravida 2, para 0 woman with an uneventful pregnancy and normal prenatal screening test results presented with sudden cessation of fetal movement at 26 weeks' gestation. Ultrasound demonstrated unexplained ARED with normal fetal growth and normal amniotic fluid volume. The fetus died during transfer to the labour and delivery unit. The cause of fetal demise was initially assumed to be feto-maternal hemorrhage, but postmortem examination revealed non-compaction of the ventricular myocardium.

CONCLUSION

Intrinsic myocardial disease should be considered in the differential diagnosis when ARED is discovered in the umbilical arteries, especially when fetal growth is normal. Postmortem examination should be performed even if a prior 18- to 20-week anatomical ultrasound has been reported as normal.

Placental diagnostic criteria and clinical correlation – a workshop report

Placental pathology is a valuable link explaining how underlying pregnancy risk factors result in adverse pregnancy outcome. This potentially useful information is currently underutilized due to a general lack of rigor in placental diagnosis. This lack of rigor is in large part due to a failure to appreciate the importance of the information provided and hence to demand accurate and clinically responsive reporting. This workshop reviewed the results of a recent initiative by the Perinatal Section of the Society for Pediatric Pathology to systematize and validate diagnostic schema for the description of lesions related to three important pathologic processes: amniotic fluid infection, maternal vascular underperfusion, and fetal vascular obstruction. This was followed by presentation of three studies correlating these pathologic processes with the following clinical outcomes: complications of prematurity, fetal growth restriction, and neurodisability following term delivery.

Discordant growth in twins

Discordant growth in twins contributes significantly to rates of perinatal morbidity and mortality. These rates vary according to chorionicity, timing of onset and severity. We have reviewed English language literature in Medline since 1980. It is clear that diagnosis of discordant growth has improved due to the use of serial ultrasound examination. Following the detection of differences in fetal size, diagnosis is facilitated by umbilical artery and fetal Doppler studies. Management options vary according to chorionicity, timing of onset and umbilical-fetal Doppler studies. The mode of delivery in discordant twins remains controversial. We conclude that ultrasound surveillance of twin gestations, combining serial biometry and selective Doppler studies, is effective in the recognition of significant intrauterine growth restriction in co-twins. Differences in etiology and management underscore the importance of establishing chorionicity routinely as soon as twin gestation is diagnosed.

Treatment Options in Fetomaternal Hemorrhage: Four Case Studies

BACKGROUND

Significant fetomaternal hemorrhage (FMH) is an uncommon event that places the fetus at risk of severe morbidity and mortality. Symptoms and signs at presentation are subtle and, if promptly recognized, appropriate management may permit the fetus to escape serious injury.

CASES

Four cases of significant FMH were diagnosed in the high-risk obstetrical unit at Mount Sinai Hospital, Toronto, during 2003. Three of the women complained of reduced fetal movements and were investigated initially with a non-stress test, a Kleihauer-Betke test, and ultrasound, including Doppler of the middle cerebral artery. These women all required emergency Caesarean section for non-reassuring fetal status. One fetus was treated by intravascular transfusion. Another identified case was transfused postnatally. One asymptomatic case was identified after spontaneous vaginal birth and also treated by neonatal transfusion. Neurological outcomes were good in all four cases.

CONCLUSIONS

Reduced fetal movements may be the only complaint of FMH. Increased awareness is required to ensure a diagnosis is made. When a non-stress test for reduced fetal movement is non-reactive, a Kleihauer-Betke test should be ordered, as well as detailed ultrasonography, including fetal Doppler studies. The perinatal prognosis for FMH may improve by facilitating the appropriate use of fetal blood transfusion or delivery by Caesarean section.

Ultrasound diagnosis of severe thrombotic placental damage in the second trimester: an observational study

OBJECTIVES

To screen women with uteroplacental insufficiency between 18 and 26 weeks' gestation for sonographic evidence of destructive placental lesions, to observe the effect of low molecular-weight heparin (LMWH) in these cases, and to compare the outcome with similar but untreated controls.

METHODS

We screened 180 women at high risk for placental damage using 16-week maternal serum screening (alpha-fetoprotein and human chorionic gonadotropin), placental shape and texture, and uterine artery Doppler waveforms at the 18-20-week level II examination. Serial gray-scale examinations of placental texture were performed at 22, 24 and 26 weeks. LMWH was offered to women with ultrasound evidence of destructive placental lesions in the absence of intrauterine growth restriction and/or pre-eclampsia.

RESULTS

We prospectively identified six women (3.3%) with abnormal maternal serum screening and uterine artery Doppler in whom abnormal placental texture (echogenic cystic lesions) suggestive of destructive lesions in the placental parenchyma was found either at the 18-20-week ultrasound examination (n = 4), or by 26 weeks of gestation (n = 2). All six received LMWH and had live births (gestational age at delivery, 33-37 weeks; birth weight, 1000-3200 g). A further 14 women were referred with similar multiparameter evidence of placental damage at or after 26 weeks, outside the screening study. All had significant fetal growth restriction and were therefore not offered heparin. In 9/14 cases there was a perinatal death. Ischemic and/or thrombotic placental pathology was confirmed in each case, but no maternal thrombophilia disorders were identified in the 20 women.

CONCLUSIONS

Integrated biochemical and ultrasound testing of placental function at 16-20 weeks of gestation, followed by serial placental gray-scale ultrasound, may be an effective method of identifying a subset of pregnancies at high risk of adverse pregnancy outcome due to destructive lesions in the placental parenchyma. This strategy of identifying thrombo-occlusive placental lesions before the development of pregnancy complications may prove useful in the design of trials to study the effectiveness of LMWH in the prevention of clinical complications resulting from thrombo-occlusive placental disease.