Screening for aneuploidies by maternal age, fetal nuchal translucency and maternal serum biochemistry at 11-13+6 gestational weeks

INTRODUCTION

Aneuploidies are the major cause of perinatal death and early psychophysical disorders.

OBJECTIVES

In this study, we analyzed detection and false-positive rates of screening for aneuploidies in the first trimester by the combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free beta-human chorionic gonadotrophin (beta-hCG), and pregnancy-associated plasma protein-A (PAPP-A) at 11-13+6 weeks of gestation, using the appropriate software developed by the Fetal Medicine Foundation.

METHODS

Our screening study for aneuploidies analyzed 4172 singleton pregnancies from January 2006 to December 2010. The sensitivities and false-positive rates using the combined aneuploidies determination for the risk cut-off of 1:275 were evaluated.

RESULTS

In the trisomy 21 pregnancies, the fetal NT was higher than 95th centile, in 72.8%, serum free b-hCG concentration it was above the 95th centile in 55% and serum PAPP-A was below the 5th centile in 47% of the cases. In the trisomy 18 and 13, the fetal NT was above 95th centile in 66.6% and 44.4% of the cases, respectively.The serum free b-hCG concentration was above the 95th centile in 0 and 10%, but serum PAPP-A was below 5th centile in 80.9% and 88.8% of pregnancies. In the trisomy 21 pregnancies the median free beta-hCG was 2.3 MoM and the median PAPP-A was 0.45 MoM. Chromosomal abnormalities were detected in 169 fetuses: trisomy 21 (97), Turner syndrome (19), trisomy 18 (28), trisomy 13 (11) and others (14). Detection rate of combined screening for aneuploides were 86.0% with false positive rate of 5.3% (mean age 33 +/- 4.9 years, > 35 years in 35% of pregnancies).

CONCLUSION

Our study suggests that the strategy of first-trimester combined screening of biochemical values and ultrasonographic parameters at 12 gestational weeks identifies higher percentage of aneuploidies with a lower false-positive rate than a single parameter strategy.

Prospective study evaluating performance of first-trimester combined screening for trisomy 21 using repeat sampling of maternal serum markers PAPP-A and free β-hCG

OBJECTIVE

To prospectively evaluate the performance of first-trimester combined screening for trisomy 21 using the biochemical markers pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (free β-hCG) obtained before and at the time of the nuchal translucency (NT) scan.

METHODS

Three fetal medicine departments in Denmark participated in the study. Screening for trisomy 21 was set up as a two-step approach with blood sampling performed before the NT scan (early sample) and again at the time of the NT scan (late sample). PAPP-A and free β-hCG were measured on both the early and late samples. Age-standardized detection and false-positive rates for different screening protocols were calculated.

RESULTS

We collected two blood samples in 27 pregnancies affected by trisomy 21 and in 3891 control pregnancies. The early samples were taken between gestational ages 8 + 0 and 13 + 6 weeks, and the late samples between 11 + 3 and 14 + 6 weeks. The median interval between the samples was 17 (range, 1-40) days. We found a significantly better estimated screening performance when using early sampling vs late sampling (P < 0.05). With a risk cut-off of 1 in 100, at the time of the risk assessment the estimated detection and false-positive rates when using the early sample were 91% (95% CI, 81-98%) and 1.6% (95% CI, 1.3-2.0%), respectively. For fixed false-positive rates the highest detection rates were achieved using both blood samples. When comparing early sampling vs double sampling there was no significant difference in screening performance.

CONCLUSION

In combined first-trimester screening for trisomy 21, use of early sampling with measurement of PAPP-A and free β-hCG before the time of the NT scan can optimize screening performance. Using maternal serum markers obtained both before and at the time of the NT scan has the potential to further improve performance, but larger studies are needed to confirm this potential.

[Modern methods of early screening for preeclampsia and pregnancy-induced hypertension--a review]

Preeclampsia remains to be a serious perinatal complication and early screening for this disease to identify the high risk population before the first symptoms develop constitutes a considerable clinical challenge. Modern methods of screening for preeclampsia and pregnancy-induced hypertension include patients history biochemical serum markers and foetal DNA and RNA in maternal serum. They aid the process of developing an optimal protocol to initiate treatment in early pregnancy and to reduce the rate of complications. Our review presents an overview of the novel methods and techniques used for early screening for preeclampsia and pregnancy-induced hypertension. Most of the research focuses on 11-13 weeks of gestation due to the fact that the first prenatal examination is performed at that time. The most important information seems to be: weight, mass, mean blood pressure, history of pregnancy-induced hypertension or preeclampsia at previous pregnancies as well as the ethnic origin. During an ultrasound scan, pulsatility index of the uterine arteries is measured. Blood samples are obtained during the last part of the examination. At the moment only a few markers seem to be strong predictors of hypertensive disorders during pregnancy: pregnancy-associated plasma protein-A (PAPP-A), placental growth factor (PIGF) and soluble fms-like tyrosine kinase-1 (sFlt-1). Also, fetal DNA and RNA in maternal plasma are helpful in the prediction of preeclampsia as they are markers of the trophoblast apoptosis. Researchers aim at identifying the population at high risk of pregnancy-induced hypertension and preeclampsia in order to offer appropriate antenatal care to these women. At the moment many drugs and diet supplements are investigated to reduce the prevalence of hypertensive disorders in pregnancy. These medications are usually administrated in early gestation (up to 16 week of gestation) before the first clinical symptoms present. Low doses of aspirin were found to decrease the risk of preeclampsia in high-risk groups. Moreover, according to some recent research, also essential omega-3 fatty acids reduce the incidence of preeclampsia. None of the other investigated diet supplements or antioxidants were proven to successfully reduce incidents of hypertensive disorders. So far, there is available evidence on the lack of any effect for vitamines C, D or E. Further studies are necessary to define clinical useful markers of gestational hypertension.

Significance of IGFBP-4 in the development of fetal growth restriction

BACKGROUND

Fetal growth restriction (FGR) is a leading cause of perinatal mortality and morbidity. Animal studies suggest dysregulation of IGF-binding protein (IGFBP)-4 is significant in the development of FGR, although human data are lacking. We postulated that IGFBP-4 is expressed at the maternal fetal interface and plays a role in regulating IGF bioavailability. Thus, maternal serum levels of IGFBP-4 may be associated with complications of abnormal placental growth and development including FGR.

METHODS

Circulating levels of IGFBP-4 and its protease, pregnancy-associated plasma protein-A (PAPP-A), were examined in healthy pregnancies. Their expression in villi and bed as possible sources of the circulating products were examined by immunohistochemistry. From the large Ottawa and Kingston (OaK) Birth Cohort, a nested case-control study was conducted to examine circulating levels of IGBP-4, PAPP-A, IGF-I, and IGF-II by Western blot in early gestation in 36 women who went on to develop FGR and 36 controls having normal-weight babies.

RESULTS

IGFBP-4 was elevated in early pregnancy compared with nonpregnant women and women in later pregnancy, consistent with the presence of abundant extravillous trophoblasts and decidual cells that highly expressed IGFBP-4. High expression of PAPP-A was observed in extravillous trophoblasts and decidual cells in early pregnancy but hardly detectable in the circulation at this time, suggesting maternal circulating PAPP-A originates more likely from syncytiotrophoblasts. Increased IGFBP-4 in the maternal circulation in early pregnancy was associated with the development of FGR [0.48 (0.28-0.74) in control vs. 1.22 (0.66-1.65) in FGR; odds ratio = 22 (95% confidence interval = 2.7-181)]. No difference was observed in circulating PAPP-A, IGF-I and IGF-II in the FGR vs. control group.

CONCLUSION

Our findings support the role of IGFBP-4 in regulating IGF bioavailability and provide new clues for the prevention and treatment of FGR, raising the possibility of clinical use of IGFBP-4 as an early biomarker for this condition.

Predictors of poor perinatal outcome following maternal perception of reduced fetal movements--a prospective cohort study

Background

Maternal perception of reduced fetal movement (RFM) is associated with increased risk of stillbirth and fetal growth restriction (FGR). RFM is thought to represent fetal compensation to conserve energy due to insufficient oxygen and nutrient transfer resulting from placental insufficiency.

Objective

To identify predictors of poor perinatal outcome after maternal perception of reduced fetal movements (RFM).

Design

Prospective cohort study.

Methods

305 women presenting with RFM after 28 weeks of gestation were recruited. Demographic factors and clinical history were recorded and ultrasound performed to assess fetal biometry, liquor volume and umbilical artery Doppler. A maternal serum sample was obtained for measurement of placentally-derived or modified proteins including: alpha fetoprotein (AFP), human chorionic gonadotrophin (hCG), human placental lactogen (hPL), ischaemia-modified albumin (IMA), pregnancy associated plasma protein A (PAPP-A) and progesterone. Factors related to poor perinatal outcome were determined by logistic regression.

Results

22.1% of pregnancies ended in a poor perinatal outcome after RFM. The most common complication was small-for-gestational age infants. Pregnancy outcome after maternal perception of RFM was related to amount of fetal activity while being monitored, abnormal fetal heart rate trace, diastolic blood pressure, estimated fetal weight, liquor volume, serum hCG and hPL. Following multiple logistic regression abnormal fetal heart rate trace (Odds ratio 7.08, 95% Confidence Interval 1.31–38.18), (OR) diastolic blood pressure (OR 1.04 (95% CI 1.01–1.09), estimated fetal weight centile (OR 0.95, 95% CI 0.94–0.97) and log maternal serum hPL (OR 0.13, 95% CI 0.02–0.99) were independently related to pregnancy outcome. hPL was related to placental mass.

Conclusion

Poor perinatal outcome after maternal perception of RFM is closely related to factors which are connected to placental dysfunction. Novel tests of placental function and associated fetal response may provide improved means to detect fetuses at greatest risk of poor perinatal outcome after RFM.

Assessment of serum leptin, pregnancy-associated plasma protein A and CRP levels as indicators of plaque vulnerability in patients with acute coronary syndrome

INTRODUCTION

A multifactorial aetiology of coronary artery disease (CAD) has been established in the recent past. Extensive research is now underway to understand the mechanisms responsible for plaque vulnerability. The identification of a novel biomarker that will help in the assessment of plaque status is urgently needed for the purpose of patient stratification and prognostication. The aim of the present study was to evaluate leptin, pregnancy-associated plasma protein A (PAPP-A) and C-reactive protein (CRP) levels in patients with acute coronary syndrome and to assess their diagnostic efficacy in the identification of vulnerable plaques.

METHODS

The study group comprised 105 patients who had chest pain along with ECG changes (ST elevation, ST depression, T inversion) and raised cardiac enzyme levels. Sixty-two patients with chest pain and ECG changes but with normal cardiac enzyme profiles were included in the control group. Lipid profiles, and leptin, PAPP-A and CRP levels were assessed in these two groups. Receiver operating characteristics (ROC) curves were plotted to determine the utility of the parameters under study as markers of plaque vulnerability.

RESULTS

Significantly higher levels of serum lipoprotein (a), leptin, PAPP-A and high-sensitivity CRP (hs-CRP) were observed in the cases than in the controls. A positive correlation was observed between CRP and PAPP-A levels as well as CRP and leptin concentrations. ROC curve analysis revealed similar efficacies of CRP and PAPP-A levels in their ability to detect unstable plaques with areas under the curve of 0.762 and 0.732, respectively. Multivariate analysis established the superiority of hs-CRP as a predictor of plaque instability.

CONCLUSIONS

Our study highlights the utility of both CRP and PAPP-A levels as determinants of plaque instability. Our findings necessitate population-based follow-up studies to establish the superiority of either of the two biomarkers in the field of preventive cardiology.

First-trimester prediction of preeclampsia in nulliparous women at low risk

OBJECTIVE

To identify clinical characteristics and biochemical markers in first-trimester samples that would possibly predict the subsequent development of preeclampsia.

METHODS

We conducted a multicenter observational study in 2,434 nulliparous women at low risk to identify biomarkers that possibly predict preeclampsia. Clinical history, complete blood count, and biochemical markers were assessed in the first trimester. The trophoblast and angiogenesis markers ADAM-12, pregnancy-associated plasma protein-A, placental protein 13, placental growth factor, soluble fms-like tyrosine kinase-1, and endoglin were measured in a case-control subset of 174 women with preeclampsia and 509 women in the control group.

RESULTS

Univariable analysis revealed maternal age, race, marital status, years of education, source of medical payment, prenatal caregiver, body mass index (BMI, calculated as weight (kg)/[height (m)]), and systolic blood pressure at enrollment were significantly associated with preeclampsia. Mean platelet volume was greater at enrollment in women who later had development of preeclampsia (median 9.4 compared with 9.0 femtoliter (fl); P=.02). First-trimester concentrations (multiples of the median) of ADAM-12 (1.14 compared with 1.04; P=.003), pregnancy-associated plasma protein-A (0.94 compared with 0.98; P=.04), and placental growth factor (0.83 compared with 1.04; P<.001) were significantly different in women who had development of preeclampsia compared with women in the control group. The optimal multivariable model included African American race, systolic blood pressure, BMI, education level, ADAM-12, pregnancy-associated plasma protein-A, and placental growth factor, and yielded an area under the curve of 0.73 (95% confidence interval 0.69-0.77) and a sensitivity of 46.1% (95% confidence interval 38.3-54.0) for 80% specificity.

CONCLUSION

A multivariable analysis of clinical data and biochemical markers in the first trimester did not identify a model that had clinical utility for predicting preeclampsia in a nulliparous population at low risk.

LEVEL OF EVIDENCE

II.

Pregnancy associated plasma protein-A (PAPP-A) as an early marker for the diagnosis of acute coronary syndrome

AIMS AND OBJECTIVES

Pregnancy associated plasma protein-A (PAPP-A), a metalloproteinase plays a pivotal role in the pathogenesis of atherosclerosis. Recent studies have reported that elevated levels of PAPP-A, signal the onset of acute coronary syndrome (ACS). We, therefore, proposed to study the analytical competence of PAPP-A in patients admitted to the emergency department with chest pain and finally diagnosed as ACS.

METHODS AND RESULTS

Pregnancy associated plasma protein-A was measured using enzyme-linked immunosorbent assay (ELISA) in 485 patients admitted to emergency care unit, of which 89 patients were diagnosed as Non-cardiac chest pain (NCCP). Elevated levels of PAPP-A were observed in patients diagnosed as ACS on comparison with the controls. Receiver operator characteristic (ROC) curve analysis showed PAPP-A to be a good discriminator between ischaemic and non-ischaemic patients. The area under the curve was found to be 0.904, 95% CI (0.874-0.929) with 90% sensitivity and 85% specificity (P< 0.0001). The cut-off value from the ROC curve was 0.55 μg/mL above which PAPP-A was considered to be positive.

CONCLUSION

Pregnancy associated plasma protein-A seems to be a promising biomarker for identification and risk stratification for patients with ACS.

Cost effectiveness, the economic considerations of prenatal screening strategies for trisomy 21 in the Czech Republic

OBJECTIVES

To perform an incremental cost-effectiveness analysis for screening of trisomy 21 (Down syndrome) in the Czech Republic through a decision tree model designed to evaluate the costs and potential risks involved in using different strategies of screening. METHODS AND DATA ANALYSIS: Using decision-analysis modelling, we compared the cost-effectiveness of nine possible screening strategies for trisomy 21: 1. maternal age > or = 35 in first trimester, 2. maternal age > or = 35 in second trimester, 3. second trimester triple test (AFP, hCG, mu E3), 4. nuchal translucency measurement, 5. first trimester serum test (PAPP-A, fbeta-hCG), 6. first trimester combined (nuchal translucency, PAPP-A, fbeta-hCG) not in OSCAR manner, 7. first trimester combined (nuchal translucency, PAPP-A, fbeta-hCG) in OSCAR manner, 8. first trimester combined (nuchal translucency, nasal bone, PAPP-A, fbeta-hCG) not in OSCAR manner, 9. first trimester combined (nuchal translucency, nasal bone, PAPP-A, fbeta-hCG) in OSCAR manner. The analysis is performed from a health care payer perspective using relevant cost and outcomes related to each screening strategy in a cohort of 118,135 pregnant women presenting around 12 weeks of pregnancy in the Czech Republic. Using a computer spreadsheet Excel (Microsoft Corporation, Redmond, Wash) the following outcomes: overall cost-effectiveness, trisomy 21 cases detected, trisomy 21 live birth prevented and euploid losses from invasive procedures were obtained. The incremental cost-effectiveness ratios were also calculated by a comparison of strategy nine and strategy three (the current practice in the Czech Republic).

RESULTS

Under the baseline assumptions, the model favors strategy nine as the most cost-effective trisomy 21 screening strategy. This strategy was the least expensive strategy per trisomy 21 cases averted. Although all the other strategies cost less, they all had lower trisomy 21 detection rates and higher numbers of procedure-related losses (except for strategies six and seven, which had same loss rate) compared with strategy nine. All strategies considered were cheaper compared with screening only by maternal age over 35 years. Adding the nasal bone and the OSCAR manner made strategy nine the most cost-effective one. The incremental cost-effectiveness (cost per additional trisomy 21 case prevented) comparing strategy nine and second trimester triple test (current practice in Czech Republic) yielded an additional baseline cost of 219,326 CZK. This would seem not to save money but due to the low false positive rate the test is less costly than might be expected and it is more cost-effective than the current practice in the Czech Republic (3,580,082 CZK for the current practice and 2,469,833 CZK for our strategy in terms of costs per DS case prevented).

CONCLUSION

In our analysis the NT, NB, PAPP-A and fbeta-hCG combined test carried out in the first trimester was the most cost-effective screening strategy for trisomy 21 in the Czech Republic.

Association of first trimester low PAPP-A levels with adverse pregnancy outcomes

OBJECTIVE

To investigate whether first trimester low PAPP-A levels are associated with adverse pregnancy outcomes.

METHODS

A case control retrospective study including 663 pregnant women whose gestational age ranged between 11 and 14 weeks attending prenatal care at Akdeniz University Hospital was carried out. Chromosomal abnormalities, spontaneous abortions, and multiple pregnancies were excluded from the study. Finally 318 singleton pregnancies were included in this study. Pregnant women whose PAPP-A levels were < or =10th percentile were compared with PAPP-A levels > 10'h percentile for the frequency of pregnancy complications such as SGA, preeclampsia, preterm delivery, gestational diabetes mellitus and gestational hypertension.

RESULTS

The most common complication of pregnancy was SGA (9.4%, n=30). There was no significant association between low PAPP-A levels and incidence of subsequent pregnancy outcomes. Maternal age was found to be a risk factor for gestational diabetes (p = 0.00). Small for gestational age was significantly associated with nulliparity and smoking during pregnancy (p = 0.03 and p = 0.01, respectively).

CONCLUSION

First trimester of low PAPP-A level (< or = 10th percentile) was not associated with SGA, preeclampsia, preterm delivery, gestational hypertension or gestational diabetes mellitus.

First trimester serum levels of 25-hydroxyvitamin D, free β-human chorionic gonadotropin, and pregnancy-associated plasma protein A in Spanish women

BACKGROUND

Vitamin D has been implicated in embryo/placental development and growth; however information in this regard is limited or unavailable.

OBJECTIVE

To assess 25-hydroxyvitamin D (25(OH)D), free β-human chorionic gonadotropin (β-hCG) and pregnancy associated plasma protein A (PAPP-A) status during pregnancy.

METHODS

Serum 25(OH)D, β-hCG, and PAPP-A levels were measured in the first trimester of otherwise healthy Spanish pregnant women (n=488). Rho Spearman coefficients were calculated to determine correlations between analytes.

RESULTS

Median serum 25(OH)D levels for the entire sample was 27.4 ng/ml (interquartile range=12.1). 25(OH)D levels were insufficient (20-29.99 ng/ml) and deficient (<20 ng/ml) in 40.6% and 23.2%, respectively, in relation to ethnics, body mass index values, tobacco use, and season/gestational age at blood sampling. β-hCG and PAPP-A levels significantly correlated (r²=0.47) yet neither of them with 25(OH)D levels. Despite this, the three analytes significantly correlated with gestational age at sampling.

CONCLUSION

First trimester 25(OH)D, β-hCG, and PAPP-A levels increase with gestational age; however, placental peptides do not correlate with vitamin D levels, suggesting a non-placental 25(OH)D production. More research is required in this regard.

Implementation of One-Stop-Clinic for Risk Assessment of chromosomal abnormalities in the first trimester, evaluating the effectiveness and making it part of our daily practice

OBJECTIVES

Implementation and introducing of first trimester screening using nuchal translucency (NT), nasal bone (NB), maternal serum pregnancy associated plasma protein-A and free beta-human chorionic gonadotropin (PAPP-A and fbeta-hCG) as a new method of screening for Down's Syndrome in a One-Stop-Clinic for Assessment of Risk for chromosomal abnormalities in the Czech Republic. To prove its effectiveness and make it part of our daily practice. Modify and/or withdraw the existing current practice.

METHODS

Prospective study of 5010 singleton pregnancies who attended our clinic for prenatal screening for chromosomal and congenital abnormalities between 11-13+6 weeks gestation from January 2005 to December 2007. Pregnancies were followed up to ascertain live birth of Down syndrome babies.

CONCLUSION

The uptake was 100% for screening and around 95% for invasive testing in the screen positive group. All expected trisomies 21 were detected along with many other aneuploidies for false positive rate of 4.4%. The study demonstrated the feasibility and efficacy of introducing OSCAR for chromosomal abnormalities in a University Hospital setting. The introduction of an examination of nasal bone reduced our false positive results and increased our sensitivity. Women who participated in our screening strategy were no longer advised to undergo the triple test.

First-trimester placental protein 13, PAPP-A, uterine artery Doppler and maternal characteristics in the prediction of pre-eclampsia

OBJECTIVE

To test the hypothesis that a combination of PP13, PAPP-A and first-trimester uterine artery Doppler would improve the prediction of pre-eclampsia.

METHODS

This is a prospective cohort study of pregnant women followed from the first-trimester to delivery. PP13 and PAPP-A were determined by immunoassay of maternal serum at 11-14 weeks', when uterine artery Doppler measurements were assessed. Cases identified with any form of pre-eclampsia were compared with a control group without pre-eclampsia. The sensitivity of each marker or their combinations in predicting pre-eclampsia for different fixed false positive rates was calculated from the ROC curves.

RESULTS

Forty two women were diagnosed with pre-eclampsia and 410 women with pregnancies not complicated by pre-eclampsia were used as controls. For a fixed false positive rate (FPR) of 20%, PP13, PAPP-A and mean uterine artery pulsatility index identified 49%, 58% and 62% respectively, of women who developed any form of pre-eclampsia. PP13 was best in predicting early onset pre-eclampsia with a sensitivity of 79% at a 20% FPR. Combinations of the three first-trimester assessments did not improve the prediction of pre-eclampsia in later pregnancy.

CONCLUSION

First-trimester PP13, PAPP-A and uterine artery PI are reasonable, individual predictors of women at risk to develop pre-eclampsia. Combinations of these assessments do not further improve the prediction of pre-eclampsia.

Prenatal screening for and diagnosis of aneuploidy in twin pregnancies

OBJECTIVE

To provide a Canadian consensus document with recommendations on prenatal screening for and diagnosis of fetal aneuploidy (e.g., Down syndrome and trisomy 18) in twin pregnancies.

OPTIONS

The process of prenatal screening and diagnosis in twin pregnancies is complex. This document reviews the options available to pregnant women and the challenges specific to screening and diagnosis in a twin pregnancy.

OUTCOMES

Clinicians will be better informed about the accuracy of different screening options in twin pregnancies and about techniques of invasive prenatal diagnosis in twins.

EVIDENCE

PubMed and Cochrane Database were searched for relevant English and French language articles published between 1985 and 2010, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis, twin gestation). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational studies. Searches were updated on a regular basis and incorporated in the guideline to August 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The previous Society of Obstetricians and Gynaecologists of Canada guidelines regarding prenatal screening were also reviewed in developing this clinical practice guideline.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

There is a need for specific guidelines for prenatal screening and diagnosis in twins. These guidelines should assist health care providers in the approach to this aspect of prenatal care of women with twin pregnancies. SUMMARY STATEMENTS 1. Fetal nuchal translucency combined with maternal age is an acceptable first trimester screening test for aneuploidies in twin pregnancies. (II-2) 2. First trimester serum screening combined with nuchal translucency may be considered in twin pregnancies. It provides some improvement over the performance of screening by nuchal translucency and maternal age by decreasing the false-positive rate. (II-3) 3. Integrated screening with nuchal translucency plus first and second trimester serum screening is an option in twin pregnancies. Further prospective studies are required in this area, since it has not been validated in prospective studies in twins. (III) 4. Non-directive counselling is essential when invasive testing is offered. (III) 5. When chorionic villus sampling is performed in non-monochorionic multiple pregnancies, a combination of transabdominal and transcervical approaches or a transabdominal only approach appears to provide the best results to minimize the likelihood of sampling errors. (II-2) Recommendations 1. All pregnant women in Canada, regardless of age, should be offered, through an informed counselling process, the option of a prenatal screening test for the most common clinically significant fetal aneuploidies. In addition, they should be offered a second trimester ultrasound for dating, assessment of fetal anatomy, and detection of multiples. (I-A) 2. Counselling must be non-directive and must respect a woman's right to accept or decline any or all of the testing or options offered at any point in the process. (III-A) 3. When non-invasive prenatal screening for aneuploidy is available, maternal age alone should not be an indication for invasive prenatal diagnosis in a twin pregnancy. (II-2A) If non-invasive prenatal screening is not available, invasive prenatal diagnosis in twins should be offered to women aged 35 and over. (II-2B) 4. Chorionicity has a major impact on the prenatal screening process and should be determined by ultrasound in the first trimester of all twin pregnancies. (II-2A) 5. When screening is done by nuchal translucency and maternal age, a pregnancy-specific risk should be calculated in monochorionic twins. In dichorionic twins, a fetus-specific risk should be calculated. (II-3C) 6. During amniocentesis, both amniotic sacs should be sampled in monochorionic twin pregnancies, unless monochorionicity is confirmed before 14 weeks and the fetuses appear concordant for growth and anatomy. (II-2B) 7. Prior to invasive testing or in the context of twins discordant for an abnormality, selective reduction should be discussed and made available to those requesting the procedure after appropriate counselling. (III-B) 8. Monitoring for disseminated intravascular coagulopathy is not indicated in dichorionic twin pregnancies undergoing selective reduction. (II-2B).

First trimester Down syndrome screening with dried blood spots using a dual analyte free beta hCG and PAPP-A immunofluorometric assay

OBJECTIVE

To determine the effectiveness of first trimester Down syndrome screening with dried blood spots using a dual analyte free beta human chorionic gonadotrophin (hCG)/pregnancy-associated plasma protein A (PAPP-A) immunofluorometric assay.

METHOD

An initial retrospective study of 54 Down syndrome cases and 1064 control specimens was performed followed by a series of 146,513 specimens from routine screening. Detection rates at a fixed 5% false-positive rate were determined separately based on reference data from the retrospective study set and then adjusted based on the routine screening study set.

RESULTS

On the basis of the retrospective analysis, the estimated detection rate using free beta hCG, PAPP-A and maternal age varied from 78% at 9 weeks of pregnancy to 70% at 13 weeks of pregnancy. Using a combined protocol, including NT, the detection rate varied from 92 to 90% between 9 and 13 weeks of gestation. Adjusting distribution parameters based on the routine screening dataset reduced the detection rate by at most 1%.

CONCLUSION

Analysis of free beta hCG and PAPP-A using a dual analyte dried blood spot assay is an effective tool in Down syndrome screening, adding an important option for those considering implementation or modification of existing prenatal screening programs.

The impact of first trimester screening and early fetal anomaly scan on invasive testing rates in women with advanced maternal age

PURPOSE

To evaluate the acceptance of noninvasive screening for trisomy 13, 18, 21 and the impact on invasive testing rates in women at an age≥35 years.

MATERIALS AND METHODS

In a retrospective analysis from 2003-2006 including 13 268 women≥35 years old with singleton pregnancies and 3133 invasive procedures, we evaluated the prenatal detection rate of aneuploidies in two cohorts. Group 1: advanced maternal age as sole indication, group 2: additional abnormalities and/or suspicious maternal serum parameters. In an additional analysis from 1998-2006 including 31,076 patients≥35 years, we investigated the shift in time of sonography at 11+0-13+6, 14+0-17+6 and 18+0-22+6 gestational weeks (gw).

RESULTS

Among 13,268 women, 3133 invasive tests were performed with a significant decrease over time (-17%). 9% of women chose invasive testing after a normal ultrasound (group 1, n=1,267) and 14% in the case of additional markers (group 2, n=1,866). 102 cases of aneuploidy were disclosed. The proportion of detected aneuploidies was 0.86% in group 1 and 4.9% in group 2. No change in the overall detection rate (90-93%) was observed. The number of patients≥40 years increased significantly (+2.8%). There was an increase in examinations at 11+0-13+6 gw (+8%), a decrease at 14+0-17+6 gw (-10.3%) and no significant change at 18+0-22+6 gw over time.

CONCLUSION

Increasing numbers of women≥35 years of age rely on the individually adjusted risk figure to make a decision about invasive testing. The application of these selective procedures can reduce the rates of invasive testing with fewer losses of normal fetuses and led to an earlier diagnosis of aneuploidies.

Assessment of the ductus venosus, tricuspid blood flow and the nasal bone in second-trimester screening for trisomy 21

OBJECTIVE

To examine the prevalence of reversed a-wave in the ductus venosus, tricuspid regurgitation and absent nasal bone, in a second-trimester population undergoing amniocentesis, after exclusion of major fetal defects and to estimate the performance in screening for trisomy 21 based on maternal age and these markers in a general population.

METHODS

This was a retrospective study involving pregnancies undergoing amniocentesis due to increased risk for trisomy 21, mainly because of advanced maternal age. Before the invasive procedure, an ultrasound examination was carried out to exclude major fetal defects and to examine the ductus venosus, tricuspid blood flow and the presence of the fetal nasal bone. Modeling techniques were used based on 20 000 euploid pregnancies and 20 000 pregnancies with trisomy 21 to assess the screening performance in a general population.

RESULTS

The study population consisted of 3613 euploid pregnancies and 35 cases with trisomy 21. In the euploid group, reversed flow in the ductus venosus, tricuspid regurgitation and an absent nasal bone was observed in 1.7%, 1.5% and 0.1% of cases, respectively. In the trisomic group, these markers were found in 14.3%, 11.4% and 14.3% of cases, respectively. For a 5% false-positive rate, the detection rate in screening for trisomy 21, based on maternal age and either ductus venosus, tricuspid blood flow or nasal bone would be 33.8%, 32.4% or 31.4%, respectively. Screening by maternal age alone would detect 29.0% of the fetuses with trisomy 21. Receiver-operating characteristics curve analysis showed a slight but significant improvement in screening performance for trisomy 21 based on the inclusion of these markers.

CONCLUSION

Second-trimester ultrasound screening for trisomy 21 based on maternal age with additional assessment of the ductus venosus, tricuspid blood flow and the fetal nasal bone in otherwise normal-appearing fetuses is only marginally better than is screening by maternal age alone.

Are age cutoffs still used to identify candidates for invasive testing for chromosomal abnormalities?

OBJECTIVE

Our objective was to determine whether women > or = age 35 are more likely to undergo invasive testing after risk adjustment as compared with younger women at similar adjusted risk.

STUDY DESIGN

Results of first-trimester combined aneuploidy risk assessment of singleton pregnancies from 2007-2008 were reviewed. For each level of adjusted risk, the rate of invasive testing (CVS or amniocentesis) was compared for those < age 35 and those > or = age 35. Spearman correlation, Fisher's exact test, and chi2 for trend were used for statistical comparison.

RESULTS

For all categories except adjusted risk of 1 in < or = 250, women > or = age 35 were significantly more likely to undergo invasive testing as compared with younger women of similar risk. In women > or = age 35 with low adjusted risk, we observed a trend towards lower rates of invasive testing over time.

CONCLUSION

The higher rate of invasive testing in those > or = 35 indicates that women are still being categorized based on age, though our data suggest this may be decreasing.

Histomorphometric characteristics of first trimester chorionic villi in pregnancies with low serum pregnancy-associated plasma protein-A levels: relationship with placental three-dimensional power doppler ultrasonographic vascularization

OBJECTIVE

To evaluate histomorphometric vascular characteristics from samples obtained by chorionic villus sampling (CVS) in pregnancies with low serum pregnancy-associated plasma protein-A (PAPP-A) levels and to relate these findings to three-dimensional (3D) placental volume and power Doppler vascularization.

METHODS

Immediately before CVS, placental 3D-power Doppler ultrasonography was performed at 11 + 0 to 13 + 6 weeks in 12 pregnancies with PAPP-A concentrations <0.3 multiples of median (MoM) as well as in 11 control women. Using a standardized setting placental volume, vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were measured. Histomorphometric parameters of villi were blindly evaluated with a video-computerized-image-analysis system.

RESULTS

Pregnancies with low PAPP-A showed a significantly reduced number of capillary vessels per villus cross-section (p = 0.005) and a smaller capillary diameter (p = 0.041). Placental vascular indices were significantly related to the number of fetal capillary vessels per villus (VI: r = 0.51, p = 0.03; FI: r = 0.48, p = 0.04; VFI: r = 0.56, p = 0.01).

CONCLUSIONS

Differences in placental vascularization are present in first trimester in pregnancies with low PAPP-A and they are associated to altered 3D placental Doppler indices.

A reassessment of biochemical marker distributions in trisomy 21-affected and unaffected twin pregnancies in the first trimester

OBJECTIVE

To estimate the difference between levels of the two biochemical markers pregnancy-associated plasma protein-A (PAPP-A) and maternal serum free β-human chorionic gonadotropin (free β-hCG) in twin pregnancies relative to singleton pregnancies and establish an improved screening procedure for chromosomal abnormalities such as trisomy 21 in twin pregnancies.

METHODS

4843 unaffected and 47 trisomy 21-affected twin pregnancies were included in the study. Chorionicity-specific medians were generated for PAPP-A and free β-hCG from gestational ages 8 to 14 weeks. Multiple of the median values for each of the biochemical markers were calculated. Detection rates and false-positive rates were estimated for screening tests incorporating nuchal translucency and maternal age, with and without biochemistry.

RESULTS

Medians for the two biochemical markers for monochorionic and dichorionic twins in unaffected pregnancies show a gestational age-specific increase relative to singleton medians. Allowing for gestation and chorionicity, twin pregnancies affected with trisomy 21 had higher levels of free β-hCG and lower levels of PAPP-A. Adding biochemistry into the risk assessment using a fixed risk cut-off of 1 in 100 increased the detection rate for fetal trisomy 21 in dizygotic twin pregnancies from 78 to 90%, and decreased the false-positive rate from 8.0 to 5.9%.

CONCLUSION

Generation of chorionicity-specific medians for the biochemical markers and their use in risk assessment can improve the performance of first-trimester screening for chromosomal abnormalities in twins to a level comparable with that in singleton pregnancies.