Circulating angiogenic factors in singleton vs multiple-gestation pregnancies

The addition of the sFlt-1/PlGF ratio to the protein/creatinine ratio in multiple pregnancy: Post-hoc analysis of the PREPARE cohort study

OBJECTIVE

To assess the predictive accuracy of the sFlt-1/PlGF ratio cut-off 38 in addition to the standard-of-care spot urine protein/creatinine ratio (PCr) for multiple pregnancies in women with suspected pre-eclampsia.

STUDY DESIGN

Post-hoc analysis of a prospective cohort study.

MAIN OUTCOME MEASURES

Primary outcome was the occurrence of pre-eclampsia in one and four weeks after presentation with suspected pre-eclampsia. Test characteristics with 95% confidence intervals (CI) were calculated on pre-eclampsia development in one and four weeks.

RESULTS

Twenty-three multiple pregnancies with suspected pre-eclampsia between 20 and 37 weeks gestation were included for analysis. Women who eventually developed pre-eclampsia had a significantly higher PCr (34.0 vs. 16.5, p = 0.015), sFlt-1 (17033 vs. 5270 pg/ml, p = 0.047) and sFlt-1/PlGF ratio (99 vs. 25, p = 0.033) at baseline. Furthermore, PCr ≥ 30 and sFlt-1/PlGF ratio > 38 was respectively seen in 1/16 (6.3 %) and 3/16 (18.8 %) of the women who did not develop pre-eclampsia. For predicting pre-eclampsia within one week the sFlt-1/PlGF ratio sensitivity was 75.0 % [95 % CI 19.4-99.4] and the negative predictive value 93.8 % [73.0-98.8], while no pre-eclampsia developed when PCr was < 30. Consequently, the combination of these tests did not lead to an improvement in test characteristics, with non-significant differences in positive predictive value (50.0 % [29.5-70.5] versus 80.0 % [37.3-96.4]) compared to PCr alone for pre-eclampsia development in one week.

CONCLUSIONS

In addition to standard-of-care spot urine PCr measurements, this study has not been able to demonstrate that the sFlt-1/PlGF ratio cut-off 38 is of added value in the prediction of pre-eclampsia in multiple pregnancy.

TRIAL REGISTRATION

Netherlands Trial Register (NL8308).

Plasma soluble fms-like tyrosine kinase 1 to placental growth factor ratio of 11.5 multiples of median predicts preeclampsia with severe features within 2 weeks of testing

BACKGROUND

Angiogenic imbalances, characterized by an excess of antiangiogenic factors (soluble fms-like tyrosine kinase 1) and reduced angiogenic factors (vascular endothelial growth factor and placental growth factor), contribute to the mechanisms of disease in preeclampsia. The ratio of soluble fms-like tyrosine kinase 1 to placental growth factor has been used as a biomarker for preeclampsia, but the cutoff values may vary with gestational age and assay platform.

OBJECTIVE

This study aimed to compare multiples of the median of the maternal plasma soluble fms-like tyrosine kinase 1 to placental growth factor ratio, soluble fms-like tyrosine kinase 1, placental growth factor, and conventional clinical and laboratory values in their ability to predict preeclampsia with severe features.

STUDY DESIGN

We conducted a cohort study across 18 United States centers involving hospitalized individuals with hypertension between 23 and 35 weeks' gestation. Receiver operating characteristic curve analyses of maternal plasma biomarkers, highest systolic or diastolic blood pressures, and laboratory values at enrollment were performed for the prediction of preeclampsia with severe features. The areas under the curve were compared, and quasi-Poisson regression models were fitted to estimate relative risks. The primary outcome was preeclampsia with severe features within 2 weeks of enrollment. Secondary outcomes were a composite of severe adverse maternal outcomes (elevated liver enzymes, low platelets count, placental abruption, eclampsia, disseminated intravascular coagulation, and pulmonary edema) and a composite of severe adverse perinatal outcomes (birth weight below the third percentile, very preterm birth [<32 weeks' gestation], and fetal or neonatal death).

RESULTS

Of the 543 individuals included in the study, preeclampsia with severe features within 2 weeks was observed in 33.1% (n=180) of them. A receiver operating characteristic curve-derived cutoff of 11.5 multiples of the median for the soluble fms-like tyrosine kinase 1 to placental growth factor plasma ratio provided good sensitivity (90.6%), specificity (76.9%), positive predictive value (66.0%), negative predictive value (94.3%), positive likelihood ratio (3.91), negative likelihood ratio (0.12), and accuracy (81.4%) for preeclampsia with severe features within 2 weeks. This cutoff was used to compare test positive cases (≥ cutoff) and test negative cases (< cutoff). Preeclampsia with severe features (66.0% vs 5.7%; P<.001) and composites of severe adverse maternal (8.11% vs 2.7%; P=.006) or perinatal (41.3% vs 10.14%; P=.001) outcomes within 2 weeks were more frequent in test positive cases than in test negative cases. A soluble fms-like tyrosine kinase 1 to placental growth factor plasma ratio ≥11.5 multiples of the median was independently associated with preeclampsia with severe features (adjusted incidence rate ratio, 9.08; 95% confidence interval, 6.11-14.06; P<.001) and a composite of severe adverse perinatal outcomes (adjusted incidence rate ratio, 9.42; 95% confidence interval, 6.36-14.53; P<.001) but not with a composite of severe adverse maternal outcomes (adjusted incidence rate ratio, 2.20; 95% confidence interval, 0.95-5.54; P=.08). The area under the curve for the soluble fms-like tyrosine kinase 1 to placental growth factor plasma ratio in multiples of the median (0.91; 95% confidence interval, 0.89-0.94) for preeclampsia with severe features within 2 weeks was significantly higher (P<.001 for all comparisons) than either plasma biomarker alone or any other parameter with the exception of absolute soluble fms-like tyrosine kinase 1 to placental growth factor plasma ratio values.

CONCLUSION

A soluble fms-like tyrosine kinase 1 to placental growth factor plasma ratio ≥11.5 multiples of the mean among hospitalized patients with hypertension between 23 and 35 week's gestation predicts progression to preeclampsia with severe features and severe adverse perinatal outcomes within 2 weeks.

Comparative analysis of risk factors for retinopathy of prematurity in single and multiple birth neonates

AIM

To conduct a comparative analysis of risk factors for retinopathy of prematurity (ROP) in single- and multiple-born neonates.

METHODS

In a retrospective evaluation of 521 premature neonates, encompassing singletons, twins, and triplets born at or before 34 weeks of gestational age with a birthweight of less than 2000 g and who completed the ROP screening program, between 2020 and 2023, in outpatient referral ROP screening clinic affiliated by Shiraz University of Medical Sciences, were included. Neonates with the eligibility criteria were enrolled in the screening program from 28 days old age and followed up to discharge or treatment based on national ROP screening guideline. Data on ROP severity, outcome, treatment modality, and risk factors, including gestational age (GA), birth weight (BW), sex, duration of neonatal intensive care unit (NICU) admission, oxygen supplementation, mechanical ventilation, blood transfusion, method of delivery, and maternal and neonatal comorbidities, were extracted and compared between premature neonates from singleton and multiple births.

RESULTS

The analysis of the ROP severity distribution revealed 238 neonates (45.7%) with low-risk (type 2 prethreshold ROP or less severe) ROP and 16 (3.1%) with high-risk (type I prethreshold ROP or more severe) ROP who underwent treatment. According to the comparative analysis of risk factors in neonates with ROP requiring treatment, multiple birth neonates exhibited significantly greater GA (27.50 ± 3.27 vs. 30.00 ± 2.00 vs. 31.14 ± 0.38 weeks, p = 0.032 for singletons, twins and triplets, respectively); greater BW (861.67 ± 274.62 vs. 1233.33 ± 347.75 vs. 1537.14 ± 208.86 g, p = 0.002); and shorter duration of NICU admission (60.17 ± 21.36 vs. 34.00 ± 12.17 vs. 12.00 ± 6.32 days, p = 0.001) and oxygen supplementation (47.33 ± 16.57 vs. 36.00 ± 8.49 vs. 4.60 ± 2.41 days, p = 0.001). There was no significant difference between single-born neonates and multiple-born neonates regarding the prevalence of other risk factors. Multiple-born neonates with no ROP and low risk ROP showed significantly lower GA and BW compared to singletons (p < 0.001).

CONCLUSION

Multiple gestation neonates may develop high-risk ROP requiring treatment at a greater gestational age and birth weight and at a lower duration of oxygen supplementation and NICU admission compared to the single birth neonates. This pattern prompts a reevaluation of screening criteria, suggesting a potential need to consider multiple birth neonates with lower traditional risk factors in screening programs. This pattern should be further evaluated in larger populations of multiple born premature neonates.

Translation of mechanistic advances in preeclampsia to the clinic: Long and winding road

As one of the leading causes of premature birth and maternal and infant mortality worldwide, preeclampsia remains a major unmet public health challenge. Preeclampsia and related hypertensive disorders of pregnancy are estimated to cause >75 000 maternal and 500 000 infant deaths globally each year. Because of rising rates of risk factors such as obesity, in vitro fertilization and advanced maternal age, the incidence of preeclampsia is going up with rates ranging from 5% to 10% of all pregnancies worldwide. A major discovery in the field was the realization that the clinical phenotypes related to preeclampsia, such as hypertension, proteinuria, and other adverse maternal/fetal events, are due to excess circulating soluble fms-like tyrosine kinase-1 (sFlt-1, also referred to as sVEGFR-1). sFlt-1 is an endogenous anti-angiogenic protein that is made by the placenta and acts by neutralizing the pro-angiogenic proteins vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). During the last decade, this work has spawned a new era of molecular diagnostics for early detection of this condition. Antagonizing sFlt-1 either by reducing production or blocking its actions has shown salutary effects in animal models. Further, in early-stage human studies, the therapeutic removal of sFlt-1 from maternal circulation has shown promise in delaying disease progression and improving outcomes. Recently, the FDA approved the first molecular test for preterm preeclampsia (sFlt-1/PlGF ratio) for clinical use in the United States. Measuring serum sFlt-1/PlGF ratio in the acute hospital setting may aid short-term management, particularly regarding step-up or step-down of care, decision to transfer to settings better equipped to manage both the mother and the preterm neonate, appropriate timing of administration of steroids and magnesium sulfate, and in expectant management decisions. The test itself has the potential to save lives. Furthermore, the availability of a molecular test that correlates with adverse outcomes has set the stage for interventional clinical trials testing treatments for this disorder. In this review, we will discuss the role of circulating sFlt-1 and related factors in the pathogenesis of preeclampsia and specifically how this discovery is leading to concrete advances in the care of women with preeclampsia.

sFlt-1 Levels as a Predicting Tool in Placental Dysfunction Complications in Multiple Pregnancies

BACKGROUND

several studies have demonstrated that angiogenic markers can improve the clinical management of hypertensive disorders (HDs) and fetal growth restriction (FGR) in singleton pregnancies, but few studies have evaluated the performance of these tests in multiple pregnancies. Our aim was to investigate the role of soluble fms-like tyrosine kinase 1 (sFlt-1) in predicting adverse obstetric outcomes in hospitalized multiple pregnancies with HD (preeclampsia/gestational hypertension/uncontrolled chronic hypertension) and/or FGR in one or more fetuses.

METHODS

A retrospective analysis of multiple pregnancies with HD/FGR occurring after the 20th gestational week. Pregnant women were divided into two groups: women with high levels of sFlt-1 and those with low levels of sFlt-1. A value of sFlt-1 greater than or equal to 15,802 pg/mL was considered arbitrarily high, as it is equivalent to two times the 90th percentile expected in an uncomplicated full-term singleton pregnancy based on data from a prospective multicenter study (7901 pg/mL).

RESULTS

The cohort included 39 multiple pregnancies. There were no cases of birth <34 weeks, HELLP syndrome, ICU admission, and urgent cesarean sections for HD/FGR complications reported among women with low levels of sFlt-1.

CONCLUSIONS

A cut-off value of sFlt-1 ≥ 15,802 pg/mL could represent a valuable tool for predicting adverse obstetric outcomes in multiple pregnancies hospitalized for HD/FGR disorders, regardless of gestational age and chorionicity.

sFLT1, PlGF, the sFLT1/PlGF Ratio and Their Association with Pre-Eclampsia in Twin Pregnancies-A Review of the Literature

Twin pregnancies demonstrate a 2-3-fold higher chance of developing PE compared to singletons, and recent evidence has demonstrated that the sFLT1/PIGF ratio is strongly associated with PE, adverse pregnancy outcomes, as well as imminent deliveries due to PE complications. The primary objective of this systematic review was to summarise the available data on the levels of sFLT1, PlGF and their ratios in twin pregnancies and to investigate their association with the development of PE, adverse pregnancy outcomes and the timing of the delivery. A systematic search of Ovid Embase, Web of Science, Science Direct, PubMed, Ovid Medline, Google Scholar and CINAHL was carried out. sFLT1 levels and the sFLT1/PIGF ratio appeared higher in twins compared to singleton pregnancies, especially in the third trimester, while PlGF levels appeared higher up until the third trimester, with their values showing no difference or being even lower than in singletons thereafter. The sFLT1/PIGF ratio has been reported to be an independent marker of adverse outcomes related to pre-eclampsia and is associated with the mean time until delivery in an inverse manner. Further research is required in order to establish the optimal sFLT1/PIGF cut-off values and to stratify the risk of adverse outcomes in twin pregnancies.

Perspectives on the Use of Placental Growth Factor (PlGF) in the Prediction and Diagnosis of Pre-Eclampsia: Recent Insights and Future Steps

Pre-eclampsia (PE) is a complex multisystem disease of pregnancy that is becoming increasingly recognized as a state of angiogenic imbalance characterized by low concentrations of placental growth factor (PlGF) and elevated soluble fms-like tyrosine kinase (sFlt-1). PlGF is a protein highly expressed by the placenta with vasculogenic and angiogenic properties, which has a central role in spiral artery remodeling and the development of a low-resistance placental capillary network. PlGF concentrations are significantly lower in women with preterm PE, and these reduced levels have been shown to precede the clinical onset of disease. Subsequently, the clinical utility of maternal serum PlGF has been extensively studied in singleton gestations from as early as 11 to 13 weeks' gestation, utilizing a validated multimarker prediction model, which performs superiorly to the National Institute for Health and Care Excellence (NICE) and American College of Obstetricians and Gynecologists (ACOG) guidelines in the detection of preterm PE. There is extensive research highlighting the role of PlGF-based testing utilizing commercially available assays in accelerating the diagnosis of PE in symptomatic women over 20 weeks' gestation and predicting time-to-delivery, allowing individualized risk stratification and appropriate antenatal surveillance to be determined. "Real-world" data has shown that interpretation of PlGF-based test results can aid clinicians in improving maternal outcomes and a growing body of evidence has implied a role for sFlt-1/PlGF in the prognostication of adverse pregnancy and perinatal events. Subsequently, PlGF-based testing is increasingly being implemented into obstetric practice and is advocated by NICE. This literature review aims to provide healthcare professionals with an understanding of the role of angiogenic biomarkers in PE and discuss the evidence for PlGF-based screening and triage. Prospective studies are warranted to explore if its implementation significantly improves perinatal outcomes, explore the value of repeat PlGF testing, and its use in multiple pregnancies.

sFlt-1, Not PlGF, Is Related to Twin Gestation Choronicity in the First and Third Trimesters of Pregnancy

Background: Preeclampsia occurs more often in dichorionic than in monochorionic twin pregnancy. We hypothesize that serum concentrations of biomarkers: placental growth factor (PlGF), serum soluble fms-like tyrosine kinase-1 (sFlt-1), and endoglin (Eng) differ between monochorionic and dichorionic twin pregnancies. Methods: A prospective observational study including 43 monochorionic and 36 dichorionic twin gestation was conducted. Blood samples were collected twice from all participants: between 11 + 0 and 13 + 6 and between 32 + 0 and 34 + 0 weeks of gestation. PlGF, sFlt-1 and Eng were measured using immnunoenzymatic assays. Results: We found a significantly higher concentration of sFlt-1 in dichorionic in comparison to monochorionic pregnancies in both the first and third trimesters. PlGF and sEng levels did not differ between mono- and dichorionic gestation in both study periods. sFlt-1 level was related to twin gestation chorionicity, while PlGF expression was not. PlGF, sFlt-1 and sEng concentrations increased significantly during gestation and were much higher in the third trimester compared to the values measured in the first trimester. Conclusions: Angiogenic biomarkers expression differ between dichorionic and monochorionic twin pregnancy. The sFlt-1 level is related to chorionicity of a twin gestation.

A comparative study of two immunoassays of maternal placental growth factor

Circulating maternal levels of placental growth factor correlates well with placental function and numerous studies advocate its role to help rule-out preterm pre-eclampsia. A number of automated immunoassay platforms to quantify placental growth factors are currently available. The aim of this study was to highlight the importance of developing and validating appropriate reference ranges and clinical cut-offs for immunoassays, by comparing the results obtained from two different immunoassays of placental growth factor; the Quantikine^® ELISA and the automated Triage^® test. This was a secondary subgroup analysis of samples collected as part of a prospective cross-sectional study of placental growth factors in twin pregnancy. Consenting pregnant women with a twin pregnancy, across a variety of gestations, had a single blood sample taken at a one-time point only during their pregnancy. The plasma was initially biobanked and then later analysed in batches using both immunoassays. Although the placental growth factor values of the two immunoassays correlated well (r = 0.88, n = 178, p < .001), the actual results obtained were significantly different (mean difference 238.1 pg/ml). Poor concordance between the two immunoassays was also present, with the Triage^® test recording 36 cases as <100 pg/ml whereas the Quantikine^® ELISA identified only 4 as <100 pg/ml. Biomarker levels may vary significantly between different immunoassay platforms, highlighting the importance of developing validated clinical cut-offs for any automated immunoassay before its clinical application. These differences need to be understood to facilitate clinical utility given that placental growth factor testing is likely to be introduced into widespread clinical practice.

Gestational Age-Specific Reference Ranges for the sFlt-1/PlGF Immunoassay Ratio in Twin Pregnancies

OBJECTIVE

Establish reference ranges for the Elecsys® soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) immunoassay ratio in twin pregnancies.

METHODS

Data analyzed were from 3 prospective studies: Prediction of Short-Term Outcome in Pregnant Women with Suspected Preeclampsia (PE) (PROGNOSIS), Study of Early-onset PE in Spain (STEPS), and a multicenter case-control study. Median, 5th, and 95th percentiles for sFlt-1, PlGF, and the sFlt-1/PlGF ratios were determined for normal twin pregnancies for 7 gestational windows and compared with the previous data for singleton pregnancies.

RESULTS

The reference range analysis included 269 women with normal twin pregnancies. Before 29 weeks' gestation, median, 5th, and 95th percentiles for sFlt-1/PlGF ratios did not differ between twin and singleton pregnancies. From 29 weeks' gestation to delivery, median, 5th, and 95th percentiles for sFlt-1/PlGF ratios were substantially higher in twin versus singleton pregnancies. sFlt-1 values were higher in women with twin pregnancies across all gestational windows. PlGF values were similar or higher in twin versus singleton pregnancies; PlGF concentrations increased from 10 weeks + 0 days to 28 weeks + 6 days' gestation.

CONCLUSIONS

Reference ranges for the sFlt-1/PlGF ratio are similar in women with twin and singleton pregnancies until 29 weeks' gestation but appear higher in twin pregnancies thereafter.

Hypertensive Disorders of Pregnancy and Subsequent Risk of Premature Mortality

BACKGROUND

Hypertensive disorders of pregnancy (HDPs) are leading causes of maternal and perinatal morbidity and mortality. However, it is uncertain whether HDPs are associated with long-term risk of premature mortality (before age 70 years).

OBJECTIVES

The objective of this study was to evaluate whether HDPs were associated with premature mortality.

METHODS

Between 1989 and 2017, the authors followed 88,395 parous female nurses participating in the Nurses' Health Study II. The study focused on gestational hypertension and pre-eclampsia within the term HDPs. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between HDPs and premature mortality were estimated by using Cox proportional hazards models, with adjustment for relevant confounders.

RESULTS

The authors documented that 2,387 women died before age 70 years, including 1,141 cancer deaths and 212 CVD deaths. The occurrence of HDPs, either gestational hypertension or pre-eclampsia, was associated with an HR of 1.31 (95% CI: 1.18 to 1.46) for premature death during follow-up. When specific causes of death were examined, these relations were strongest for CVD-related mortality (HR: 2.26; 95% CI: 1.67 to 3.07). The association between HDPs and all-cause premature death persisted, regardless of the subsequent development of chronic hypertension (HR: 1.20 [95% CI: 1.02 to 1.40] for HDPs only and HR: 2.02 [95% CI: 1.75 to 2.33] for both HDPs and subsequent chronic hypertension).

CONCLUSIONS

An occurrence of HDPs, either gestational hypertension or pre-eclampsia, was associated with an increased risk of premature mortality, particularly CVD mortality, even in the absence of chronic hypertension.

A prospective study of placental growth factor in twin pregnancy and development of a dichorionic twin pregnancy specific reference range

OBJECTIVE

To develop a dichorionic twin pregnancy specific reference range for placental growth factor (PlGF), and to compare gestation-specific placental growth factor levels in twin pregnancies later complicated by pre-eclampsia, hypertensive disorder of pregnancy or fetal growth restriction with control pregnancies.

DESIGN

Prospective observational study.

SETTING

Single large tertiary maternity unit in Ireland.

POPULATION OR SAMPLE

Women with a twin pregnancy.

METHODS

Consenting pregnant women, across a variety of gestations, had a single blood sample taken at one time-point only during their pregnancy. The plasma was initially biobanked and PlGF was measured later in batches using the point of care Triage^® PlGF test.

MAIN OUTCOME MEASURES

Development of pre-eclampsia, hypertensive disorder of pregnancy or fetal growth restriction.

RESULTS

Placental growth factor levels in uncomplicated dichorionic twin pregnancies were significantly lower in the women who later developed pre-eclampsia than in the controls at all gestational intervals. In those that later developed any hypertensive disorder of pregnancy, median PlGF was lower only in those recruited before 24 weeks of gestation, whereas in infants with a customised birthweight below the third centile, PlGF was lower only in those sampled after 24 weeks of gestation.

CONCLUSIONS

Placental growth factor levels in twin pregnancy differ significantly between those women with a pregnancy that will later be complicated by pre-eclampsia and those that will not. This difference is present many weeks before clinical signs or symptoms of disease are present. Using cross-sectional values from uncomplicated twin pregnancies, we have developed a dichorionic twin pregnancy specific reference range for PlGF.

TWEETABLE ABSTRACT

Placental growth factor levels in twin pregnancy differ significantly between women that will later develop pre-eclampsia and those that will not.

Maternal Serum Placental Growth Factor, Soluble Fms-Like Tyrosine Kinase-1, and Soluble Endoglin in Twin Gestations and the Risk of Preeclampsia-A Systematic Review

Multiple gestation is one of the key risk factors for the occurrence of preeclampsia (PE). Soluble fms-like tyrosine kinase-1, placental growth factor, and soluble endoglin are molecules involved in the process of angiogenesis with a proven role in the pathogenesis of PE. The aim of the review was to summarize available data on maternal serum levels of the above-mentioned factors and their usefulness in predicting PE in twin pregnancies. Only original research articles written in English were considered eligible. Reviews, chapters, case studies, conference papers, experts’ opinions, editorials, and letters were excluded from the analysis. No publication date limitations were imposed. The systematic literature search using PubMed/MEDLINE, Scopus, Embase, and Cochrane Library databases identified 338 articles, 10 of which were included in the final qualitative analyses. The included studies showed significant differences in maternal serum levels of the discussed factors between women with twin pregnancies with PE and those who did not develop PE, and their promising performance in predicting PE, alone or in combination with other factors. The identification of the most effective algorithms, their prompt introduction to the clinical practice, and further assessment of the real-life performance should become a priority.

The predictive value of the sFlt-1/PlGF ratio on short-term absence of preeclampsia and maternal and fetal or neonatal complications in twin pregnancies

OBJECTIVE

A sFlt-1/PlGF ratio of ≤38 has been reported to predict the absence of preeclampsia (PE) in singleton pregnancies. We evaluated whether a sFlt-1/PlGF ratio of ≤38 could be used to predict the absence of PE in twin pregnancies and maternal and fetal/neonatal complications.

METHODS

This is a secondary analysis of a prospective multicenter cohort study that enrolled women with suspected or confirmed PE with the aim of evaluating the use of the sFlt-1, PlGF and their ratio to predict maternal and fetal/neonatal complications. Twin and singleton pregnancies with clinically suspected or confirmed PE were matched for gestational age and parity. Blood samples were drawn at time of study entry, but serum values of sFlt-1 and PlGF and their ratio were determined postpartum.

RESULTS

Twenty-one women with twin and 21 with singleton gestations were included at a median gestational age of 30 weeks. At inclusion PE was diagnosed in 13 twin and 15 singleton pregnancies. In comparison to singleton control pregnancies, twin controls had a significantly higher sFlt-1 (6377 vs. 1732 pg/ml, p = 0.008), a higher sFlt-1/PlGF ratio 26 vs. 3 p = 0.361) and a lower PlGF (228 vs. 440 pg/ml p = 0.479). Compared to singleton preeclamptic pregnancies values of sFlt-1 (9134 vs. 8625 pg/ml) did not differ, whereas values of PlGF (185 vs. 33 pg/ml, p < 0.001) were higher and values of the ratio (49 vs. 158, p = 0.002) were lower in preeclamptic twin pregnancies. All preeclamptic patients with a singleton pregnancy had a ratio >38, but only 5 of the 13 patients with a preeclamptic twin pregnancy. Conversely, the ratio was ≤38 in 5 of the 6 control singleton, but in only 4 of the 8 control twin pregnancies. When classified according to a ratio ≤38 or >38 at inclusion, maternal complications occurred more frequently in patients with a ratio >38 both in singleton and twin pregnancies. In singleton pregnancies fetal/neonatal complications, except one admission to NICU, only occurred in patients with a ratio >38. In twin pregnancies fetal/neonatal complications occurred equally frequent in women with a ratio ≤38 or >38.

CONCLUSION

Serum sFlt-1 levels are considerably higher in twin than in singleton control gestations. A sFlt-1/PlGF ratio of ≤38 to predict short-term absence of PE is not applicable to twin pregnancies in predicting either the absence of PE or the absence of adverse pregnancy outcomes.

Clinical Outcome in Singleton and Multiple Pregnancies with Placental Chorangioma

INTRODUCTION

Chorangiomas (CAs) are the most common non-trophoblastic tumor-like-lesions of the placenta. Although the clinical significance of small CAs is unknown, the large lesions are often associated with maternal and fetal complications. The aim of our study was to assess the maternal clinical characteristics and neonatal outcome in singleton and multiple pregnancies with placental CA.

MATERIALS AND METHODS

Among 15742 selected placentas 170 CAs were diagnosed. Pregnancy and neonatal outcomes were analyzed in singleton (n = 121) and multiple (n = 49) pregnancy groups including 121 and 100 neonates, respectively.

RESULTS

The frequency of APGAR score <7 at 5 minutes (p = 0,012), abnormal pulsatility index (p = 0,034), and abnormal blood flow class (p = 0,011) were significantly higher in neonates from singleton compared to multiple pregnancies. Significantly smaller CAs in singleton pregnancies were related to small for gestational age neonates (p = 0,00040) and neonates admitted to the neonatal care unit (p = 0,028). In singleton pregnancies, significantly smaller CAs were associated to maternal preeclampsia (p = 0,039) and larger CAs to multiparity (p = 0,005) and smoking (p = 0,001) groups. The frequency of preeclampsia was high in both singleton and multiple pregnancy groups (41,32% vs 26,53%, respectively), however, the difference did not reach the level of statistical significance.

DISCUSSION

A high incidence of preeclampsia in cohort of placental CA might lead to a possible recognition of CAs as potential morphologic indicator of placental hypoxia.

CONCLUSION

A more favorable pregnancy outcome in multiple gestations compared to the singleton gestations with CAs might reflect an adaptive mechanism for increased demand of oxygen and associated placental tissue hypoxia in this group.

Genetic, immune and vasoactive factors in the vascular dysfunction associated with hypertension in pregnancy

INTRODUCTION

Preeclampsia (PE) is a major complication of pregnancy that could lead to maternal and fetal morbidity and mortality. The pathophysiological mechanisms of PE are not completely understood, but recent research has begun to unravel some of the potential mechanisms.

AREAS COVERED

Genetic polymorphisms and altered maternal immune response may cause impaired remodeling of the spiral arteries; a potential early defect in PE. Inadequate invasion of cytotrophoblasts into the decidua leads to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia causes the release of biologically active factors such as anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and angiotensin II receptor autoantibodies. These vasoactive factors could cause systemic vascular endotheliosis and consequent increase in vascular resistance and blood pressure, glomerular endotheliosis causing proteinuria, cerebrovascular endotheliosis causing cerebral edema, seizures and visual disturbances, and hepatic endotheliosis, which may contribute to the manifestations of HELLP syndrome. PE-associated vascular endotheliosis causes a decrease in vasodilator mediators such as nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor, an increase in vasoconstrictors such as endothelin-1, angiotensin II and thromboxane A2, and enhanced mechanisms of vascular smooth muscle contraction such as intracellular Ca(2+), protein kinase C and Rho-kinase. Changes in matrix metalloproteinase activity and extracellular matrix cause vascular remodeling and further vasoconstriction.

EXPERT OPINION

Some of the genetic, immune and vasoactive factors involved in vascular endotheliosis could be used as biomarkers for early detection, and as potential targets for prevention and treatment of PE.

Circulating Levels of sFlt1 Splice Variants as Predictive Markers for the Development of Preeclampsia

Angiogenic biomarkers, including soluble fms-like tyrosine kinase 1 (sFlt1), are thought to be predictors of preeclampsia onset; however, improvement is needed before a widespread diagnostic test can be utilized. Here we describe the development and use of diagnostic monoclonal antibodies specific to the two main splice variants of sFlt1, sFlt1-1 and sFlt1-14. These antibodies were selected for their sensitivity and specificity to their respective sFlt1 isoform in a capture ELISA format. Data from this pilot study suggest that sFlt1-1 may be more predictive of preeclampsia than total sFlt1. It may be possible to improve current diagnostic platforms if more specific antibodies are utilized.

Maternal circulating angiogenic factors in twin and singleton pregnancies

OBJECTIVE

The purpose of this study was to compare longitudinally sampled maternal angiogenic proteins between singleton and twin pregnancies.

STUDY DESIGN

Placental growth factor (PlGF), soluble feline McDonough sarcoma (fms)-like tyrosine kinase (sFlt)-1, and soluble endoglin from healthy pregnant women were quantified at 10, 18, 26, and 35 weeks' gestation (n=91), and during the third trimester (31-39 weeks) and at delivery (33-41 weeks; n=41). Geometric means and 95% confidence intervals were calculated for gestational age-adjusted angiogenic protein concentrations and compared between matched twin and singleton pregnancies.

RESULTS

Maternal sFlt-1 concentrations and the sFlt-1/PlGF ratio were higher in twins than singletons across pregnancy and at delivery, with the greatest differences at week 35 (sFlt-1: 36,916 vs 10,151 pg/mL; P<.0001; sFlt-1/PlGF: 168.4 vs 29.0; P<.0001). Maternal concentrations of soluble endoglin also were higher in the third trimester and delivery. Maternal PlGF concentrations were lower in twin than singleton pregnancies at week 35 only (219.2 vs 350.2 pg/mL; P<.0001). Placental weight appeared to be inversely correlated with maternal sFlt-1/PlGF ratio at the end of pregnancy in both twins and singletons.

CONCLUSION

Higher maternal antiangiogenic proteins in twin than singleton pregnancies does not appear to be due to greater placental mass in the former, and may be one explanation for the increased risk of preeclampsia in women carrying multiple gestations. Determining whether women with a history of multiple gestations have an altered cardiovascular disease and breast cancer risk, like those with a history of preeclampsia, is warranted.

Angiogenic and inflammatory biomarkers in midpregnancy and small-for-gestational-age outcomes in Tanzania

OBJECTIVE

We sought to investigate the relationship between a panel of angiogenic and inflammatory biomarkers measured in midpregnancy and small-for-gestational-age (SGA) outcomes in sub-Saharan Africa.

STUDY DESIGN

Concentrations of 18 angiogenic and inflammatory biomarkers were determined in 432 pregnant women in Dar es Salaam, Tanzania, who participated in a trial examining the effect of multivitamins on pregnancy outcomes. Infants falling below the 10th percentile of birthweight for gestational age relative to the applied growth standards were considered SGA. Multivariate binomial regression models with the log link function were used to determine the relative risk of SGA associated with increasing quartiles of each biomarker. Restricted cubic splines were used to test for nonlinearity of these associations.

RESULTS

A total of 60 participants (13.9%) gave birth to SGA infants. Compared to those in the first quartile, the risk of SGA was reduced among those in the fourth quartiles of vascular endothelial growth factor-A (adjusted risk ratio [RR], 0.38; 95% confidence interval [CI], 0.19-0.74), placental growth factor (adjusted RR, 0.28; 95% CI, 0.12-0.61), soluble fms-like tyrosine kinase-1 (adjusted RR, 0.48; 95% CI, 0.23-1.01), monocyte chemoattractant protein-1 (adjusted RR, 0.48; 95% CI, 0.25-0.92), and leptin (adjusted RR, 0.46; 95% CI, 0.22-0.96).

CONCLUSION

Our findings provide evidence of altered angiogenic and inflammatory mediators, at midpregnancy, in women who went on to deliver SGA infants.

Angiogenic biomarkers for prediction of early preeclampsia onset in high-risk women

OBJECTIVE

Chronic hypertension, pregestational diabetes mellitus, history of prior preeclampsia and obese nulliparity are maternal conditions associated with increased preeclampsia risk. Whether altered maternal angiogenic factor levels allow for prediction of pending disease is unclear. Our objective was to evaluate angiogenic factors for early preeclampsia prediction in high-risk women.

METHODS

Serial serum specimens were collected from 157 women at high preeclampsia risk and 50 low-risk controls between 23 and 36 weeks gestation in 3 windows (23-27.6, 28-31.6, and 32-35.6 weeks) in a two-center observational cohort. Soluble fms-like tyrosine kinase-1 (sFlt1), placental growth factor (PlGF) and soluble endoglin (sEng) were measured by ELISA.

RESULTS

Multivariate parsimonious logistic regression analyses using backward elimination for prediction of early-preeclampsia (diagnosed < 34 weeks) found the best-fitting model included the predictors (1) sFlt1 measured in the second window (28-31.6 weeks) with AUC 0.85, sensitivity 67% and specificity 96% and (2) sFlt1 measured in the first window (23-27.6 weeks) and sEng change between first and second window with AUC 0.91, sensitivity 86% and specificity 96%.

CONCLUSIONS

Two-stage sampling screening protocol utilizing sFlt1 and sEng is promising for prediction of preeclampsia diagnosed before 34 weeks. Larger studies are needed to confirm these findings.

Gestational angiogenic biomarker patterns in high risk preeclampsia groups

OBJECTIVE

Several conditions are associated with increased preeclampsia (PE) risk. Whether altered maternal angiogenic factor levels contribute to risk in these conditions is unknown. Our objective was to compare angiogenic biomarker patterns in high-risk pregnancies and low-risk controls.

STUDY DESIGN

We conducted a planned secondary analysis of a 2-center observational study of angiogenic biomarkers in high-risk women. A total of 156 pregnant women with a PE risk factor and 59 low-risk controls were studied. Serial maternal serum samples were collected during 3 gestational windows: 23-27 weeks, 28-31 weeks, and 32-35 weeks. Soluble fms-like tyrosine kinase 1 (sFlt1), soluble endoglin (sEng), and placental growth factor (PlGF) were measured by enzyme-linked immunosorbent assay. Geometric mean angiogenic biomarker levels and angiogenic ratio (sFlt1 + sEng):PlGF were compared with low-risk controls for each risk group, at each gestational window.

RESULTS

Gestational biomarker patterns differed in PE risk groups as compared with low-risk controls. Women with multiple gestations had markedly higher sFlt1 and sEng at all gestational windows. Women with prior PE had higher sFlt1 and angiogenic ratio, and lower PlGF, from 28 weeks onward. Women with chronic hypertension had significantly higher angiogenic ratio for all 3 gestational windows, but differences disappeared when women with PE were excluded. Obese and nulliparous women had significantly lower PlGF, but no differences in the angiogenic ratio.

CONCLUSION

High-risk groups have altered angiogenic biomarker patterns compared with controls, suggesting that altered production or metabolism of these factors may contribute to PE risk, particularly in women with multiple gestations and prior PE.

Angiogenic factors in preeclampsia and related disorders

During fetal development, the human placenta undergoes high levels of both angiogenesis and vasculogenesis. Additionally, the developing placenta undergoes a process of vascular mimicry (referred to as pseudovasculogenesis) as cytotrophoblasts convert from an epithelial to an endothelial phenotype. The initiation, maturation, and maintenance of the placental vasculature are of critical importance. Failure to do so can lead to adverse obstetric outcomes such as preeclampsia and/or intrauterine growth restriction (IUGR). Furthermore, the foundation of many aspects of adult health is laid in utero. In this context, normal placental function is not only critical for normal fetal development but can also permanently influence long-term health and disease. Understanding the mechanisms that regulate placental vasculogenesis and angiogenesis is therefore of critical importance. This chapter will focus on placental vascular development with a particular emphasis on the role of angiogenic factors in the pathogenesis of the maternal syndrome of preeclampsia and related disorders.

Preeclampsia and hypertensive disease in pregnancy: their contributions to cardiovascular risk

More women than men die each year of cardiovascular disease, which remains the leading cause of death in the United States. Sex-specific factors, including pregnancy-related disorders, should be considered when assessing cardiovascular (CV) risk in women. Hypertensive disorders of pregnancy have been associated with CV risk later in life and may identify women in whom earlier primary prevention may reduce their risk. This article reviews the physiologic changes in blood pressure during pregnancy, current definitions of hypertensive diseases of pregnancy and preeclampsia, and postulated pathophysiologic mechanisms leading to preeclampsia that might contribute to later CV risk. Also summarized are studies providing evidence on the association between hypertensive diseases of pregnancy and future CV risk.

Circulating angiogenic factors and risk of adverse maternal and perinatal outcomes in twin pregnancies with suspected preeclampsia

To evaluate whether angiogenic factor levels correlate with preeclampsia-related adverse maternal and perinatal outcomes in women with twin pregnancy, we studied 79 women with suspected preeclampsia in the 3rd trimester. Antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and proangiogenic placental growth factor (PlGF) were measured at presentation on an automated platform. An adverse outcome was defined as hemolysis, elevated liver enzymes, and low platelets syndrome; disseminated intravascular coagulation; abruption; pulmonary edema; cerebral hemorrhage; maternal, fetal, and neonatal death; eclampsia; acute renal failure; small for gestational age; and indicated delivery. All outcomes were ascertained 2 weeks after initial evaluation. Comparing the 52 women (65.8%) who experienced an adverse outcome with the 27 women (34.2%) without an adverse outcome, the median sFlt-1 was elevated (11461.5 pg/mL [8794.0-14847.5] versus 7495.0 pg/mL [3498.0-10482.0; P=0.0004]), PlGF was reduced (162.5 pg/mL [98.0-226.5] versus 224.0 pg/mL [156.0-449.0]; P=0.005), and sFlt-1/PlGF ratio was elevated (74.2 [43.5-110.5] versus 36.2 [7.1-71.3]; P=0.0005). Among those presenting <34 weeks (n=40), the difference in sFlt-1/PlGF ratio was more striking (97.7 [76.6-178.1] versus 31.7 [6.5-48.7]; P=0.001). Addition of sFlt-1/PlGF to the highest systolic blood pressure and proteinuria improved prediction of adverse outcomes. We conclude that in women with twin pregnancy and suspected preeclampsia, the sFlt-1/PlGF ratio at the time of initial evaluation is associated with subsequent adverse maternal and perinatal outcomes. These findings are similar to those in singleton pregnancies and may implicate common pathogenic pathways.

Molecular and vascular targets in the pathogenesis and management of the hypertension associated with preeclampsia

Normal pregnancy is associated with significant hemodynamic changes and vasodilation of the uterine and systemic circulation in order to meet the metabolic demands of the mother and developing fetus. Preeclampsia (PE) is one of the foremost complications of pregnancy and a major cause of maternal and fetal mortality. The pathophysiological mechanisms of PE have been elusive, but some parts of the puzzle have begun to unravel. Genetic factors such as leptin gene polymorphism, environmental and dietary factors such as Ca(2+) and vitamin D deficiency, and co-morbidities such as obesity and diabetes may increase the susceptibility of pregnant women to develop PE. An altered maternal immune response may also play a role in the development of PE. Although the pathophysiology of PE is unclear, most studies have implicated inadequate invasion of cytotrophoblasts into the uterine artery, leading to reduced uteroplacental perfusion pressure (RUPP) and placental ischemia/hypoxia. Placental ischemia induces the release of biologically active factors such as growth factor inhibitors, anti-angiogenic factors, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and antibodies to vascular angiotensin II (AngII) receptor. These bioactive factors could cause vascular endotheliosis and consequent increase in vascular resistance and blood pressure, as well as glomerular endotheliosis with consequent proteinuria. The PE-associated vascular endotheliosis could be manifested as decreased vasodilator mediators such as nitric oxide, prostacyclin and hyperpolarizing factor and increased vasoconstrictor mediators such as endothelin-1, AngII and thromboxane A₂. PE could also involve enhanced mechanisms of vascular smooth muscle contraction including intracellular Ca(2+), and Ca(2+) sensitization pathways such as protein kinase C and Rho-kinase. PE-associated changes in the extracellular matrix composition and matrix metalloproteinases activity also promote vascular remodeling and further vasoconstriction in the uterine and systemic circulation. Some of these biologically active factors and vascular mediators have been proposed as biomarkers for early prediction or diagnosis of PE, and as potential targets for prevention or treatment of the disease.

Soluble endoglin for the prediction of preeclampsia in a high risk cohort

OBJECTIVES

To evaluate soluble endoglin (sEng) and the soluble fms-like tyrosine kinase 1 (sFlt1) to placental growth factor (PlGF) ratio for the prediction of preeclampsia in high-risk women, and to evaluate differences in sEng between women with high-risk singleton and multiple gestation pregnancies.

STUDY DESIGN

We collected serial serum specimens from 119 women at high preeclampsia risk. sEng, sFlt1 and PlGF were measured by ELISA.

RESULTS

Among subjects who did not develop preeclampsia, mean serum sEng was significantly higher in those with multiple gestation pregnancies vs. high-risk singletons. Among women with singleton gestations, mean serum sEng was higher in subjects who developed early-onset (<34 weeks) and late-onset (>or= 34 weeks) preeclampsia, as compared with subjects without preeclampsia, from 22 weeks and 28 weeks gestation onward, respectively. The within-woman rate of change of sEng was also higher in women who later developed preeclampsia.

CONCLUSIONS

sEng is higher in women with multiple gestations vs. high-risk singleton pregnancies. In high-risk women, serum sEng is increased prior to preeclampsia onset.

Soluble fms-Like tyrosine kinase 1 (sFlt1), endoglin and placental growth factor (PlGF) in preeclampsia among high risk pregnancies

BACKGROUND

Differences in circulating concentrations of antiangiogenic factors sFlt1 and soluble endoglin (sEng) and the pro-angiogenic growth factor PlGF are reported to precede the onset of preeclampsia weeks to months in low-risk pregnant women. The objective of this study was to investigate whether similar changes can be detected in pregnant women at high-risk to develop the syndrome.

METHODS

This study is a secondary analysis of the NICHD MFMU trial of aspirin to prevent preeclampsia in high-risk pregnancies. Serum samples were available from 194 women with pre-existing diabetes, 313 with chronic hypertension, 234 with multifetal gestation, and 252 with a history of preeclampsia in a previous pregnancy. Samples collected across pregnancy were analyzed in a blinded fashion for sFlt1, sEng and PlGF.

RESULTS

The odds of developing preeclampsia were significantly increased among women with multiple fetuses for each 2-fold elevation in sFlt1, sEng and the ratio of angiogenic factors (e.g. OR 2.18, 95% CI 1.46-3.32), and significantly decreased for each 2-fold elevation in circulating PlGF (OR 0.50, 95% CI 0.30-0.82) between 7 and 26 weeks' gestation. Cross-sectional analysis of the angiogenic factors across gestation showed significant differences during the third trimester in women who develop preeclampsia compared with appropriate controls in all high-risk groups. However, when data were examined in relation to the gestational week when preeclampsia was diagnosed only sFlt1 was significantly higher 2 to 5 weeks before the clinical onset of preeclampsia and only in women with previous preeclampsia.

CONCLUSIONS

The pattern of elevated concentrations of sFlt1 and sEng, and low PlGF in high-risk pregnant subjects who develop preeclampsia is similar to that reported in low-risk pregnant women. However, differences in these factors among high-risk women who do and do not develop preeclampsia are modest, and do not appear to be clinically useful predictors in these high-risk pregnant women.

Maternal plasma and amniotic fluid angiogenic factors and their receptors in monochorionic twin pregnancies complicated by twin-to-twin transfusion syndrome

OBJECTIVE

Angiogenic factors play a role in human placentation and may be aberrant in severe twin-to-twin transfusion syndrome (TTTS). The aim of this study was to investigate the maternal plasma and amniotic fluid angiogenic factor and receptor concentrations in twin pregnancies complicated by TTTS and to evaluate the effects of fetoscopic laser ablation.

METHODS

A prospective cohort of monochorionic (MC) twins complicated by severe TTTS (n = 23) was studied between October 2006 and December 2007. A cohort of uncomplicated dichorionic (DC) (n = 12) and MC (n = 7) pregnancies were studied for comparison. Circulating angiogenic factors and their receptors were measured in the maternal plasma and the recipient twin's amniotic fluid by enzyme-linked immunosorbent assay and/or FAST Quant human angiogenesis array.

RESULTS

Plasma vascular endothelial growth factor (VEGF)-C concentrations were significantly lower in TTTS than in uncomplicated twin pregnancies (P < 0.0001). In contrast, plasma angiopoietin (Ang)-2 levels and the ratio of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) to placental growth factor (PlGF) levels were significantly increased in TTTS (P < 0.01). Plasma VEGF-D was significantly increased in advanced stage TTTS (Stage III/IV cohort; P < 0.01). This was independent of fetal size, amniotic fluid volumes or the number of apparent placental arteriovenous anastomoses. In TTTS pregnancies, amniotic fluid VEGF-C, VEGF-A, Ang-1 and the sVEGFR-1/PlGF ratio were increased compared to paired maternal plasma concentrations (P < 0.0001) while amniotic fluid concentrations of PlGF, Ang-2 and soluble tyrosine kinase with immunoglobulin-like/epidermal growth factor-like domains 2 (sTie-2) were significantly lower than plasma concentrations (P < 0.0001). No significant association between maternal plasma and amniotic fluid concentrations of angiogenic factors was noted. Plasma PlGF was transiently decreased after fetoscopic laser ablation, returning to baseline by 1 week (P = 0.0314). Fetoscopic laser ablation also affected plasma sVEGFR-1/PlGF ratio with a transient increase after therapy, followed by a significant reduction to below basal concentrations by 1 week (P = 0.0102). Only VEGF-D was significantly different (+8.3%; P = 0.0155) in amniotic fluid immediately after the completion of fetoscopic laser ablation.

CONCLUSION

Maternal angiogenic activity is decreased in severe TTTS, with an increased sVEGFR-1/PlGF ratio and concentrations of Ang-2 and VEGF-D in the maternal plasma compared to uncomplicated MC twin pregnancies. Maternal circulating PlGF concentrations decrease and the sVEGFR-1/PlGF ratio increases transiently in response to fetoscopic laser ablation, but in general the angiogenic factor and receptor concentrations studied are altered little by this therapy.

Measurement of sVEGF R1 and PlGF in serum: comparing prototype assays from Beckman Coulter, Inc. to R&D Systems microplate assays

OBJECTIVE

To compare the performance of prototype Access® sVEGF R1 and PlGF automated immunoassays from Beckman Coulter to the Quantikine® microplate ELISA assays by R&D Systems.

METHODS

Samples obtained from pregnant women, non-pregnant women and men were assayed according to manufacturers' instructions.

RESULTS

Compared to the Quantikine assays, the Access assays demonstrated improved precision, increased sensitivity, broader dynamic ranges, and reduced analysis time. The Access assays were found to be specific for free sVEGF R1 and free PlGF.

CONCLUSION

There was good correlation between the Access and Quantikine assays. Superior performance by Access assays may have important prenatal diagnostic implications.

The perinatal implications of angiogenic factors

PURPOSE OF REVIEW

To summarize recent findings relating maternal circulating levels of proteins associated with angiogenesis and the outcome of pregnancy.

RECENT FINDINGS

In preeclampsia, levels of placental growth factor (PlGF) become abnormal prior to soluble fms-like tyrosine kinase 1 (sFlt-1). Longitudinal measurement of changes in protein level are better predictors of disease than measurement at a single time point in pregnancy and also appear to be more strongly associated with early-onset disease. The levels of angiogenic proteins provide additional predictive information over abnormal uteroplacental Doppler. The preeclampsia-like phenotype of rats overexpressing sFlt-1 can be ameliorated by administration of a protein which binds and inactivates sFlt-1. Animal models demonstrate that uteroplacental ischemia leads to elevated maternal serum levels of sFlt-1 and decreased PlGF. Similarly, studies of human trophoblast cells demonstrate that hypoxia stimulates release of sFlt-1. Autocrine vascular endothelial growth factor (VEGF) has a trophic effect on the endothelium, distinct from its control of angiogenesis. By blocking this effect, elevated sFlt-1 could lead to systemic endothelial cell dysfunction, one of the key features of preeclampsia. Low levels of PlGF are associated with intrauterine growth restriction. However, in the first trimester of pregnancy, high levels of sFlt-1 were associated with reduced rates of growth restriction, preterm birth and stillbirth.

SUMMARY

Regulators of the VEGF system may have a causal role in the sequence of events leading to preeclampsia and may be targets for novel therapies. However, better knowledge of the biology is required prior to clinical trials of interventions.