Screening In Twin Pregnancies Research Articles

Cell-free DNA screening in twin pregnancies.

Cell-free DNA (cfDNA) screening for fetal aneuploidies is clinically available and exhibits better performance than conventional serum screening tests. However, data on the clinical performance of cfDNA screening in twin pregnancies are limited. In this review, we summarized the clinical performance and evaluated the feasibility of cfDNA screening in twin pregnancies based on recent studies and recommendations. The performance of cfDNA screening for trisomy 21 in twin pregnancies is similar to that in singleton pregnancies. Specifically, cfDNA screening has a higher detection rate and lower false-positive rate compared with conventional serum screening. Consequently, recent international guidelines from several academic communities have recommended that cfDNA screening for aneuploidy in twin pregnancies could be considered. Moreover, twin pregnancies can present with specific conditions, such as different zygosities and vanishing twins; therefore, individualized counseling and management are required. Further clinical studies with more twin pregnancies are required for a more accurate analysis.

1117 SNP-based Prenatal Cell-free DNA Screening in Twin Pregnancies: A New Standard of Care?

1117 SNP-based Prenatal Cell-free DNA Screening in Twin Pregnancies: A New Standard of Care?

Clinical application of noninvasive prenatal testing in twin pregnancies: a single-centre experience

Objectives To evaluate the clinical efficiency of non-invasive prenatal testing (NIPT) for fetal chromosomal aneuploidy screening in twin pregnancies. Methods A total of 1650 women with twin pregnancies were enrolled in the study, which underwent NIPT at the Southwest Hospital, Army Medical University, Chongqing, China from January 2013 to June 2022. Fetal karyotyping analysis was conducted in high-risk patients, with subsequent follow-up on pregnancy outcomes. Results In 1650 pregnancies, NIPT results showed ten cases of the fetal chromosome aneuploidy, of which six cases were true positive and four cases were false positive. The sensitivity, specificity, positive predictive value (PPV), and false-positive rate (FPR) of trisomy 21 were 100%, 99.79%, 57.14%, and 0.18%, respectively. Sensitivity, specificity, PPV, and FPR of trisomy 18 were 100%, 99.94%, 50%, and 0.06%, respectively. The sensitivity, specificity, PPV, and FPR of trisomy 13 were 100%, 100%, 100%, and 0%, respectively. No false negatives were detected and the negative predictive value (NPV) was 100% of the total. Eleven pregnancies failed the NIPT test with no-call due to the low fetal fraction (< 4%). Conclusions NIPT is a high-performing routine primary prenatal screening test in twin pregnancies, with high sensitivity and specificity in screening for fetal aneuploidy.

Performance of noninvasive prenatal screening in twin pregnancies: a retrospective study of 5469 twin pregnancies

Objectives To evaluate the performance of noninvasive prenatal screening (NIPS) for the fetal common aneuploidy screening in twin pregnancies. Methods The data of 5469 women with twin pregnancies were collected in this retrospective observational study between January 2017 and December 2018. Patients underwent NIPS as first-line screening or after standard serum screening for fetal aneuploidy. The performance of NIPS was examined, and a regression analysis was performed to investigate testing failure in cases of low fetal fraction. Results In this study, 2231 (40.8%) patients opted for NIPS as the primary prenatal screening test, and 3238 (59.2%) opted for serum screening, including 440 patients who opted for NIPS after serum screening. Among the 2671 pregnancies with available NIPS outcomes, 11 cases of aneuploidy were identified, seven of trisomy 21 and four of sex chromosome aneuploidy (SCA). The sensitivity and specificity for trisomy 21 were 100% (95% CI, 56.1–100.0%) and 100% (95% CI, 99.8–100.0%), respectively. The positive predictive value (PPV) for SCA was 40.0% (95% CI, 13.7–72.6%). No false negatives were found, with a negative predictive value (NPV) of 100% (95% CI, 99.8–100.0%) in total. In 32 pregnancies who failed NIPS test without available NIPS outcomes due to low fetal fraction, the regression analysis demonstrated that increasing BMI and assisted reproductive technology treatment were significant independent predictors. Conclusions NIPS is a high-performing routine primary prenatal screening test in twin pregnancies, with a high PPV and low false positive rate for detecting trisomy 21. It is also useful to identify common sex chromosome aneuploidies in twin pregnancies, with similar performance to that reported in singleton pregnancy.

Noninvasive prenatal screening in twin pregnancies with cell-free DNA using the IONA test: a prospective multicenter study

In singleton pregnancies, studies investigating cell-free DNA in maternal blood have consistently reported high detection rate and low false-positive rate for the 3 common fetal trisomies (trisomies 21, 18, and 13). The potential advantages of noninvasive prenatal testing in twin pregnancies are even greater than in singletons, in particular lower need for invasive testing and consequent fetal loss rate. However, several organizations do not recommend cell-free DNA in twin pregnancies and call for larger prospective studies. In response to this, we undertook a large prospective multicenter study to establish the screening performance of cell-free DNA for the 3 common trisomies in twin pregnancies. Moreover, we combined our data with that reported in published studies to obtain the best estimate of screening performance. This was a prospective multicenter blinded study evaluating the screening performance of cell-free DNA in maternal plasma for the detection of fetal trisomies in twin pregnancies. The study took place in 6 fetal medicine centers in England, United Kingdom. The primary outcome was the screening performance and test failure rate of cell-free DNA using next generation sequencing (the IONA test). Maternal blood was taken at the time of (or after) a conventional screening test. Data were collected at enrolment, at any relevant invasive testing throughout pregnancy, and after delivery until the time of hospital discharge. Prospective detailed outcome ascertainment was undertaken on all newborns. The study was undertaken and reported according to the Standards for Reporting of Diagnostic Accuracy Studies. A pooled analysis was also undertaken using our data and those in the studies identified by a literature search (MEDLINE, Embase, CENTRAL, Cochrane Library, and ClinicalTrials.gov) on June 6,2020. A total of 1003 women with twin pregnancies were recruited, and complete data with follow-up and reference data were available for 961 (95.8%); 276 were monochorionic and 685 were dichorionic. The failure rate was 0.31%. The mean fetal fraction was 12.2% (range, 3%-36%); all 9 samples with a 3% fetal fraction provided a valid result. There were no false-positive or false-negative results for trisomy 21 or trisomy 13, whereas there was 1 false-negative and 1 false-positive result for trisomy 18. The IONA test had a detection rate of 100% for trisomy 21 (n=13; 95% confidence interval, 75-100), 0% for trisomy 18 (n=1; 95% confidence interval, 0-98), and 100% for trisomy 13 (n=1; 95% confidence interval, 3-100). The corresponding false-positive rates were 0% (95% confidence interval, 0-0.39), 0.10% (95% confidence interval, 0-0.58), and 0% (95% confidence interval, 0-0.39), respectively. By combining data from our study with the 11 studies identified by literature search, the detection rate for trisomy 21 was 95% (n=74; 95% confidence interval, 90-99) and the false-positive rate was 0.09% (n=5598; 95% confidence interval, 0.03-0.19). The corresponding values for trisomy 18 were 82% (n=22; 95% confidence interval, 66-93) and 0.08% (n=4869; 95% confidence interval, 0.02-0.18), respectively. There were 5 cases of trisomy 13 and 3881 non-trisomy 13 pregnancies, resulting in a computed average detection rate of 80% and a false-positive rate of 0.13%. This large multicenter study confirms that cell-free DNA testing is the most accurate screening test for trisomy 21 in twin pregnancies, with screening performance similar to that in singletons and very low failure rates (0.31%). The predictive accuracy for trisomies 18 and 13 may be less. However, given the low false-positive rate, offering first-line screening with cell-free DNA to women with twin pregnancy is appropriate in our view and should be considered a primary screening test for trisomy 21 in twins.

Screening of fetal chromosomal aneuploidy diseases using noninvasive prenatal testing in twin pregnancies

ABSTRACTObjectives: This study was aimed to report the clinical characteristics of fetal chromosomal aneuploidy diseases using noninvasive prenatal testing (NIPT) in twin pregnancies and analyze the results in terms of chorionicity, conception, and fetal fraction.Methods: A total of 1160 women with twin pregnancies were recruited from 1 October 2015, to 1 August 2017. Next-generation sequencing technology was used to detect fetal aneuploidies, such as trisomy 21, trisomy 18, trisomy 13 and trisomy X.Results: Aneuploidy was detected using NIPT in 26 fetuses, among which 18 fetal aneuploidies occurred in only one fetus of the twins. The rate of aneuploidy was 1.3% for dichorionic diamniotic twins and 0.5% for monochorionic diamniotic twins, respectively. The rate of aneuploidy was 1.2% for spontaneous pregnancy group and 1.1% for assisted reproductive technologies group.Conclusion: In this study, detection of trisomy 21, trisomy 18, trisomy 13, and X abnormality in twin pregnancies was confirmed to be accurate. The aneuploidies mostly occurred in only one fetus of the twins, and trisomy 21 was the most common type. The prenatal diagnostic standard for NIPT in singleton pregnancies could perform well in twin pregnancies, which means NIPT can be popularized as routine prenatal screening in twin pregnancies.

Performance of non-invasive prenatal testing for trisomies 21 and 18 in twin pregnancies

BackgroundCell-free fetal DNA in maternal plasma represents a source of fetal genetic material that can be sampled noninvasively. There are ample studies confirming the accuracy of NIPT in singleton pregnancies, but there is still relatively little studies demonstrate the feasibility and clinical application of a NIPT for fetal aneuploidy screening in twin pregnancies.ResultsIn this study, we have finished 432 twin pregnancies screening by NIPT. There were 4 double chorionic dichorionic diamniotic (DCDA) cases of true positive NIPT results, including 1of T18 and 3 of T21, and 1 monochorionic diamniotic (MCDA) cases of true positive NIPT results, including 1of T21. The combined false-positive frequency for trisomies 21, 18 was 0%. Furthermore, there were 2 cases of false positive NIPT results, including 1 of T7 and 1 of sex chromosome aneuploidy. There was no false negative case, which gave a combined sensitivity and specificity of 100 and 99.53% respectively.ConclusionOur study demonstrated NIPT performed well in the detection of trisomy 21 in twin pregnancy. It is feasible and clinical applicable of NIPT for fetal aneuploidy screening in twin pregnancies. But, it needs a large number of clinical samples to demonstrate the applicability of other chromosomal abnormalities besides trisomies 21 and 18 in both singleton pregnancies and twin pregnancies.

Performance of non-invasive prenatal screening for fetal aneuploidy in twin pregnancies: a meta-analysis.

The objectives of this study were to review the published studies of non-invasive prenatal screening (NIPS) in twin pregnancies and to evaluate the performance for screening fetal trisomies 21, 18, and 13 in twin pregnancies. Ten eligible studies were included in this meta-analysis. Data analysis, heterogeneity exploring, meta-regression, and subgroup analysis were all conducted with Meta-DiSc 1.4. Quality assessments were carried out with the Quality Assessment Tool for Diagnostic Accuracy Studies. Non-invasive prenatal screening for trisomy 21 screening in twin pregnancies showed a pooled sensitivity of 0.99 (95% CI, 0.92-1.00), a specificity of 1.00 (95% CI, 0.99-1.00), a positive likelihood ratio (LR) of 116.46 (95% CI, 53.84-251.92), a negative LR of 0.11 (95% CI, 0.06-0.22), and a diagnostic odds ratio of 1297.73 (95% CI, 438.06-3844.42). But the difference of detection rates between monozygotic and dichorionic twin pregnancies was uncertain for only a very small number of monochorionic twins available. For trisomy 18 screening, the pooled sensitivity, specificity, positive LR, negative LR, and diagnostic odds ratio were 0.85 (95% CI, 0.55-0.98), 1.00 (95% CI, 0.99-1.00), 86.11 (95% CI, 32.45-228.47), 0.25 (95% CI, 0.11-0.56), and 333.90 (95% CI, 35.15-3171.78), respectively. For trisomy 13 screening, three cases in three studies were all detected accurately. The meta-analysis results from 10 eligible studies demonstrated that NIPS has both high sensitivity and specificity for trisomy 21 screening in twin pregnancies. The results for trisomy 18 screening are less satisfactory than those for trisomy 21. The performance for trisomy 13 screening could not be determined as only three cases were identified. © 2017 John Wiley & Sons, Ltd.

Developing a new algorithm for first and second trimester preeclampsia screening in twin pregnancies

ABSTRACTObjectives: Construct a new preeclampsia predicting algorithm in twins.Methods: Twins sampled at 10–13 and 16–20 gestational weeks and their marker values were log transformed into multiples of the gestation-specific medians (MoMs) for singletons and entered into a new logistic regression model with/without prior risk factors.Results: The cohort included 9 PE (18 samples) and 96 unaffected cases (175 samples) twin pregnant women. The algorithm constructed of PlGF, PAPP-A, PP13, Doppler UTPI, and MAP with prior risk factors generated an area under the curve of 0.918, 75% detection rate for 10% false-positive rate.Conclusions: The algorithm effectively forecasted twin risk to develop PE.

Second trimester maternal serum triple screening marker levels in normal twin and singleton pregnancies.

The aim of the present study was to evaluate the serum levels of α-fetoprotein (AFP), free-β-human chorionic gonadotropin (free-β-hCG) and unconjugated estriol (uE3) in second trimester maternal serum and comparative analysis of serum markers levels in normal twin and singleton pregnancies, and to evaluate the feasible methods for the screening performances of triple markers in twin pregnancy. The levels of maternal serum markers were measured by magnetic microparticle chemiluminescence immunoassay in the second trimester. TCSoft was used for calculating the risk of Down's syndrome (DS). The marker levels were compared between the twin and singleton pregnancies, along with gestational age, and the weight or age of the pregnant women. The concentrations of the maternal serum markers were higher on average in twin compared to in singleton pregnancies in the second trimester of the gestation. The levels of AFP were 2-fold higher in twin compared to those in singleton pregnancies in weeks 16, 17 and total gestational weeks. For free-β-hCG, the levels were higher in 15 and 18 gestational weeks. However, significant differences were found in all the gestational weeks for uE3. There was no correlation between the levels of markers and weight or age in the twin pregnancies. The serum marker levels of AFP, free-β-hCG and uE3 in normal twins were not all 2-fold higher compared to singleton pregnancies. The current singleton gestational age-specific model for DS screening requires further correction so that it is feasible for screening in twin pregnancies.

Model predicted Down syndrome detection rates for nuchal translucency screening in twin pregnancies

To estimate the Down syndrome detection rate for nuchal translucency (NT) screening in twins when fetus-specific risk allows for between-fetus NT correlation. The between-fetus correlation coefficient of log NT, in multiples of the median (MoM), was estimated from a series of 977 unaffected twins scanned at a single centre. Results were expressed in multiples of the normal median using a curve derived from 515 unaffected singleton pregnancies at the same centre. A screening result was classified as positive if the risk for at least one fetus exceeded the cut-off. Detection rates were estimated for a fixed 1-5% false-positive rate, at different gestational weeks, separately for risk calculation using an algorithm which takes account of between-fetus NT correlation or not. The correlation coefficient in unaffected pregnancies was 0.43 (P < 0.0001) and estimated to be 0.23 and 0.11 in discordant and concordant twins. At 12 weeks of gestation, the model predicted detection rate for a 3% false-positive rate was 68% when between-fetus correlation is not taken into account, increasing to 73% when it is applied. Similarly, for other false-positive rates and gestational weeks there was a predicted 4-6% increase in detection. Using a fetus-specific Down syndrome risk algorithm leads to a worthwhile increase in detection.

Cribado de aneuploidía en gestación gemelar: resultados de la aplicación del test combinado

ObjectiveTo evaluate the effectiveness of the Combined Test for trisomy 21 screening in twin pregnancies. To assess the performance of biochemical markers and nuchal translucency (NT) measurement in pregnancies with euploid fetuses and in twin pregnancies with one or two affected fetuses. To compare the value of markers according to chorionicity and the mode of conception. Material and methodsRetrospective study including 161 twin pregnancies. Maternal serum fß-hCG and PAPP-A were determined at 8 to 12 weeks and fetal NT was measured at 11 to 14 weeks. The individual risk of trisomy 21 was calculated in each fetus using the Combined Test. In monochorionic pregnancies, the single risk for the pregnancy was obtained with the largest NT. An invasive diagnostic procedure was offered when the risk was 1:250 or more in one or both of the fetuses. ResultsAll trisomy 21 pregnancies were identified (three pregnancies and four fetuses) by the combined testfor a false-positive rate of 6.4% of pregnancies and 3.5% of fetuses. The median fß-hCG level, expressed in MoM, was 1.72 and the median PAPP-A level was 2.01. The median NT was 1.05 MoM. Both fß-hCG and PAPP-A levels were significantly decreased in monochorionic pregnancies and PAPP-A was significantly decreased in pregnancies resulting from assisted reproduction. No significant differences were observed in NT measurement between monochorionic and dichorionic fetuses or between those conceived naturally or by assisted reproduction. ConclusionsThe combined test shows high sensitivity and specificity in screening for trisomy 21 in twin pregnancies. The differences obtained in the biochemical markers according to chorionicity or the mode of conception require confirmation in further studies with a larger number or cases.

Screening for trisomy 21 in twin pregnancies in the first trimester: an update of the impact of chorionicity on maternal serum markers

To examine the distribution of first-trimester biochemical markers of aneuploidy in twin pregnancies, and to assess whether there are differences in the distributions between monochorionic and dichorionic twins. Maternal serum-free beta-hCG and PAPP-A were measured between 11 + 0 and 13 + 6 weeks as part of a routine first-trimester screening program in conjunction with fetal nuchal translucency (NT) performed at two sites. Data from twin pregnancies were extracted from the fetal databases along with information on the chorionicty. The individual marker concentrations were expressed as weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM using data from singleton pregnancies as the reference. The overall medians were compared to those in singleton pregnancies and between monochorionic and dichorionic twins. Data was available from 1914 sets of twins. Of these, 1214 had information with respect to chorionicity, with 1024 being dichorionic and 190 being monochorionic. The overall median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM amongst twin pregnancies were 2.023 for free beta-hCG (sd log(10) MoM = 0.2611 and 2.121 for PAPP-A (sd log(10) MoM = 0.2255) -- both medians were significantly greater than the medians in singleton pregnancies (1.00 MoM). In the case of monochorionic and dichorionic twins the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected, free beta-hCG MoM's were not significantly different (1.983 v 2.041), however for PAPP-A the median weight corrected, ethnicity corrected, smoking corrected and IVF corrected MoM in monochorionic twins was significantly lower than in dichorionic twins (1.756 v 2.250) whilst the sd log(10) MoM's were not significantly different (0.2185 v 0.2167). Screening in twin pregnancies requires adjustment of the calculated MoM to account for the presence of two fetuses. In general, for free beta-hCG, this should be by dividing the observed corrected MoM by 2.023. For PAPP-A two different factors are required - 2.192 in dichorionic twins and 1.788 in monochorionic twins.

Second-trimester Down syndrome maternal serum screening in twin pregnancies: impact of chorionicity.

To evaluate the diagnostic value of second-trimester maternal serum screening for Down syndrome in twin pregnancies. On the basis of a prospective study of second-trimester maternal serum screening, we studied the distribution of alpha-fetoprotein (AFP) and free ss hCG in 3043 twin pregnancies with known outcome. There were 1561 dichorionic and 244 monochorionic pregnancies. The placental type was not available in 1238 cases. We compared 5 screening policies with the same risk, 1/250, cut-off: maternal age, maternal age corrected for the risk of having at least one affected twin in dichorionic pregnancies, maternal serum marker screening using observed AFP and free ss-hCG values divided by a factor of 2, by using the median values actually observed in the global twin population, or by the median values specific to mono- or dichorionic twins. When expressed in singleton-derived MoMs, the median was 2.10 for AFP and 2.11 for free ss-hCG. The median AFP did not differ between monochorionic and dichorionic pregnancies. The distribution of free ss-hCG was significantly shifted towards greater values in monochorionic (2.16 MoM) compared to dichorionic (2.07) pregnancies (p < 0.0001). Screened-positive and detection rates were, respectively, 6.6% and 27.3% using maternal age alone, 24.6% and 54.5% using maternal age corrected for the risk of having at least one affected twin in dichorionic pregnancies, 7.75% and 54.5% using observed AFP and free beta-hCG values divided by a factor of 2, 8.05% and 54.5% using the median values actually observed in the global twin population, and 7.75% and 54.5% using the median values specific to mono- or dichorionic twins. Trisomy 21 second-trimester maternal serum screening is feasible in twins, and is better than a policy based on maternal age alone.

First-trimester maternal serum PAPP-A, SP1 and M-CSF levels in normal and trisomic twin pregnancies.

To study PAPP-A and SP1 for biochemical trisomy screening in twin pregnancies and to investigate the role of maternal and placental compartments in marker production by comparing the levels of the decidual cytokine M-CSF with the PAPP-A and SP1 from the placenta. Thirteen twin pregnancies with at least one chromosomally abnormal fetus were compared with 68 normal twin pregnancies. Sera were obtained between 11 + 3 and 13 + 6 weeks of gestation, and PAPP-A, SP1 and M-CSF levels were determined by immunoassay. These concentrations were also compared with gestation-matched groups of 18 singleton normal pregnancies and 18 singleton Down syndrome pregnancies. PAPP-A and SP1, but not M-CSF, levels were higher in normal twin pregnancy than in normal singleton pregnancy. SP1 levels, but not PAPP-A, correlated to M-CSF. PAPP-A, but not SP1, levels were reduced in abnormal twin pregnancies, with an increasing effect according to the number of affected fetuses, and were more pronounced in pregnancies with trisomy 18 or 13 than in trisomy 21 fetuses. M-CSF was inconsistent, with a trend towards increased levels in trisomy 21. PAPP-A remains the best biochemical screening marker for fetal trisomies 21, 18 or 13, in singleton as well as in twin pregnancy. In contrast to SP1, its site of production is not likely to be restricted to the placenta. The role of the (maternally produced) M-CSF remains to be further investigated.

Routine uterine artery Doppler screening in twin pregnancies?

Routine uterine artery Doppler screening in twin pregnancies?