Nuchal translucency thickness in monochorionic multiple pregnancies: value in predicting pregnancy outcome

First trimester ultrasonographic parameters in prediction of the course and outcome of monochorionic twin pregnancies

BACKGROUND/AIM

The aim of the study was to evaluate the association and the potential predictive value of first trimester ultrasonographic parameters on the course and outcome of monochorionic diamniotic twin pregnancies.

MATERIALS AND METHODS

A prospective cohort study was undertaken of 39 healthy women with consecutive monochorionic diamniotic twin pregnancies. During first-trimester screening, crown-rump length (CRL) and nuchal translucency (NT) were measured. The intertwin discordance in CRL and NT was determined. As pregnancy outcomes we assessed twins' live-born rates, Apgar scores, birth weight, pregnancy complications, and gestational week of delivery.

RESULTS

None of the assessed pregnancy outcomes significantly correlated with standard CRL discordance ≥10%. The newly established cut-off was 3.75 mm for CRL and 1.3 mm for NT. Monochorionic diamniotic twins were delivered in a later gestational week and had better chance of survival if CRL intertwin difference was <3.75 mm. Apgar scores significantly negatively correlated only with NT of corresponding twins. When intertwin NT difference was ≥1.3 mm, twins had lower birth weight and pregnancy complications were more frequent. Regression models show that intertwin CRL difference <3.75 mm is a significant predictor of live-born monochorionic diamniotic twins.

CONCLUSION

CRL and NT in monochorionic diamniotic twin pregnancies could indicate pregnancy complications and outcomes.

Early prediction of twin-to-twin transfusion syndrome: systematic review and meta-analysis

OBJECTIVE

To assess the role of first- and early second-trimester markers in the prediction of twin-to-twin transfusion syndrome (TTTS) in monochorionic twin pregnancies.

METHODS

Electronic databases MEDLINE, EMBASE and ClinicalTrials.gov were searched from inception to April 2014, using the MeSH term 'fetofetal transfusion' in combination with phrases 'predictive value', 'sensitivity', 'specificity', 'false positive', 'false negative', 'screening', 'accuracy' and 'ROC'. Study quality was assessed using the PRISMA guidelines and QUADAS-2 tool. A meta-analysis was planned for the following predictive factors: intertwin nuchal translucency (NT) discrepancy; NT > 95^th percentile in at least one twin; intertwin crown-rump length (CRL) discrepancy as a percentage of the larger CRL; abnormal ductus venosus (DV) flow in at least one twin. The outcome assessed was TTTS, defined according to the presence of a twin oligohydramnios-polyhydramnios sequence. The diagnostic performance of the predictive factors was evaluated for each included study.

RESULTS

The electronic search identified 152 records, of which 23 were assessed in full for eligibility. We identified 13 eligible studies that reported the predictive accuracy of ultrasound parameters, measured before 16 weeks, for the development of TTTS, including a total of 1991 pregnancies, of which 323 developed TTTS. An increased risk of TTTS was associated with: intertwin NT discrepancy (positive likelihood ratio (LR+), 1.92 (95% CI, 1.25-2.96); negative likelihood ratio (LR-), 0.65 (95% CI, 0.50-0.84)); NT > 95^th percentile (LR+, 2.63 (95% CI, 1.51-4.58); LR-, 0.85 (95% CI, 0.75-0.96)); CRL discrepancy > 10% (LR+, 1.80 (95% CI, 1.05-3.07); LR-, 0.92 (95% CI, 0.81-1.05)); abnormal DV flow (LR+, 4.77 (95% CI, 1.33-17.04; LR-, 0.49 (95% CI, 0.17-1.41)). The highest sensitivities were observed for intertwin NT discrepancy (52.8% (95% CI, 43.8-61.7%)) and abnormal DV flow (50.0% (95% CI, 33.4-66.6%)).

CONCLUSION

Monochorionic twin pregnancies with intertwin NT discrepancy, NT > 95^th percentile, intertwin CRL discrepancy > 10% or abnormal DV flow on first-trimester ultrasound examination are at significantly increased risk of developing TTTS. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

The Outcome of Monochorionic Diamniotic Twins Discordant at 11 to 13+6 Weeks' Gestation

BACKGROUND

Monochorionic diamniotic (MCDA) twin pregnancies are associated with adverse perinatal outcome. Intertwin discordances at the time of nuchal translucency (NT) screening may have a value in the prediction of fetal loss or twin-to-twin transfusion syndrome. We aimed to determine the ability of intertwin NT and crown rump length (CRL) discordances among MCDA twins to predict adverse outcomes.

MATERIAL AND METHODS

All MCDA twins with a documented routine ultrasound at 11 to 13+6 weeks' gestation, and known pregnancy outcome between August 2003 and August 2012 were included. Receiver operating characteristic curves were used to determine the ideal NT and CRL discordances cut-off points that maximized the ability to predict adverse outcome, which was defined as any of: death of one or both twins, twin-to-twin transfusion syndrome, or estimated fetal weight or birth weight discordances ≥25%.

RESULTS

Of the 89 cases, 20 (22.5%) had at least one adverse outcome. NT discordance was more discriminatory of adverse outcome than was CRL discordance. The optimal values for predicting any adverse outcomes for NT were >23.7% and for CRL >3.5%. The positive predictive values for NT (52.4%) and CRL (29.8%) screening were relatively low; however, the lack of either NT or CRL discordances was more reassuring, with negative predictive values of 86.8% and 86.4%, respectively.

CONCLUSIONS

NT discordance is more predictive for adverse fetal outcome in MCDA twins than CRL discordance. Neither NT nor CRL discordance are likely to modify the intensive monitoring required for these very high-risk pregnancies.

Multiple gestations and preterm birth

Preterm birth is a major concern in modern obstetrics, and an important source of morbidity and mortality in newborns. Among twin pregnancies, especially, preterm birth is highly prevalent, and it accounts for almost 50% of the complications observed in this obstetrical population. In this article, we review the existing literature regarding the prediction and prevention of preterm birth in both symptomatic and asymptomatic twin pregnancies. In asymptomatic twin pregnancies, the best two predictive tests were cervical length (CL) measurement and cervicovaginal fetal fibronectin (fFN) testing. A single measurement of transvaginal CL at 20-24 weeks of gestation <20 mm or <25 mm is a good predictor of spontaneous preterm birth at <28, <32, and <34 weeks of gestation. A CL beyond 25 mm is associated with a 2% risk for birth before 28 weeks and with a 65% chance for a term pregnancy. Cervicovaginal fFN may be slightly less accurate than CL; however, it has a high negative predictive value in women presenting with threatened preterm labor, as <2% of these women will deliver within one week if the fFN is negative. In symptomatic twin pregnancies, no tests have proven accurate in predicting the risk of preterm birth. For the prevention of preterm birth in asymptomatic twins, regardless of CL, no treatment including bed rest, limitation of home activities, prophylactic tocolysis, progesterone, or cerclage has been shown to reduce the rate of preterm birth. Cervical pessaries might be of interest in cases where there is a short cervix (<25 mm and <38 mm, respectively) but these results need to confirmed in future trials.

Prediction of preterm birth in twin gestations using biophysical and biochemical tests

The objective of this study was to determine the performance of biophysical and biochemical tests for the prediction of preterm birth in both asymptomatic and symptomatic women with twin gestations. We identified a total of 19 tests proposed to predict preterm birth, mainly in asymptomatic women. In these women, a single measurement of cervical length with transvaginal ultrasound before 25 weeks of gestation appears to be a good test to predict preterm birth. Its clinical potential is enhanced by the evidence that vaginal progesterone administration in asymptomatic women with twin gestations and a short cervix reduces neonatal morbidity and mortality associated with spontaneous preterm delivery. Other tests proposed for the early identification of asymptomatic women at increased risk of preterm birth showed minimal to moderate predictive accuracy. None of the tests evaluated in this review meet the criteria to be considered clinically useful to predict preterm birth among patients with an episode of preterm labor. However, a negative cervicovaginal fetal fibronectin test could be useful in identifying women who are not at risk for delivering within the next week, which could avoid unnecessary hospitalization and treatment. This review underscores the need to develop accurate tests for predicting preterm birth in twin gestations. Moreover, the use of interventions in these patients based on test results should be associated with the improvement of perinatal outcomes.

First-trimester sonographic prediction of obstetric and neonatal outcomes in monochorionic diamniotic twin pregnancies

OBJECTIVES

The purpose of this study was to investigate whether discordant nuchal translucency and crown-rump length measurements in monochorionic diamniotic twins are predictive of adverse obstetric and neonatal outcomes.

METHODS

We conducted a multicenter retrospective cohort study including all monochorionic diamniotic twin pregnancies with two live fetuses at the 11-week to 13-week 6-day sonographic examination who had serial follow-up sonography until delivery. Isolated nuchal translucency, crown-rump length, and combined discordances were correlated with adverse obstetric outcomes, individually and in composite, including the occurrence of 1 or more of the following in either fetus: intrauterine growth restriction (IUGR), twin-twin transfusion syndrome (TTTS), intrauterine fetal death (IUFD), growth discordance (≥ 20%), and preterm birth before 28 weeks' gestation. Correlations with adverse composite neonatal outcomes were also studied. A receiver operating characteristic curve analysis and a logistic regression analysis with a generalized estimating equation were conducted.

RESULTS

Fifty-four of the 177 pregnancies included (31%) had an adverse composite obstetric outcome, with TTTS in 19 (11%), IUGR in 21 (12%), discordant growth in 14 (8%), IUFD in 14 (8%), and preterm birth before 28 weeks in 10 (6%). Of the 254 neonates included in the study, 69 (27%) were complicated by adverse composite neonatal outcomes, with respiratory distress syndrome being the most common (n = 59 [23%]). The areas under the curve for the combined discordances to predict composite obstetric and neonatal outcomes were 0.62 (95% confidence interval, 0.52-0.72), and 0.54 (95% confidence interval, 0.46-0.61), respectively.

CONCLUSIONS

In our population, nuchal translucency, crown-rump length, and combined discordances in monochorionic diamniotic twin pregnancies were not predictive of adverse composite obstetric and neonatal outcomes.

Ductus Venosus: A Love Story of 14 Years

Ductus venosus is a tiny vessel with a central role in fetal circulation. Combining B-mode with color and pulsed Doppler is feasible to identify this vessel and evaluate the blood flow waveform at 11 to 13 weeks. The higher prevalence of abnormal A-wave in fetuses with abnormal karyotype and/or cardiac defects turned DV evaluation into a useful marker for chromosomal abnormalities and cardiopathies. Even when combined with nuchal translucency (NT) or biochemical markers, DV blood flow evaluation contributes to an increase in sensitivity and reduces false-positive rate. Abnormal ductal flow is also related to a worse fetal and perinatal outcome. In monochorionic twin pregnancies, in addition to NT measurement at 11 to 14 weeks, the Doppler assessment of DV blood flow increases relevantly the performance of screening for those at higher risk of developing twin-to-twin transfusion syndrome. This story of 14 years surely contributed to change the way first trimester screening is being implemented.

Nuchal translucency thickness and crown rump length discordance for the prediction of outcome in monochorionic diamniotic pregnancies

BACKGROUND

Ultrasonographic features of the underlying hemodynamic changes in twin-twin transfusion syndrome (TTTS) may be present at the first trimester scan.

AIMS

To investigate the value of intertwin discordance in nuchal translucency (NT) thickness and crown-rump length (CRL) to predict TTTS and other adverse outcomes.

STUDY DESIGN

Cohort study.

SUBJECTS

One hundred and thirty-five unselected consecutive monochorionic diamniotic twin pregnancies.

OUTCOME MEASURES

NT and CRL discordance were assessed at 11 to 13(+6) weeks' gestation. Receiver-operating characteristics (ROC) curves were used to determine their predictive ability for the subsequent development of TTTS.

RESULTS

TTTS complicated 16/135 (12%) pregnancies. Four other pregnancies were complicated by selective intrauterine growth restriction (sIUGR) and 3 by miscarriage <24 weeks gestation. The median NT discordance was 15% (range 0-37%) in TTTS pregnancies, 13% (12-19%) in those with miscarriage <24 weeks' gestation, 47% (30-50%) in those with sIUGR, and 14% (0-86%) in those without complications. Prediction for subsequent development of TTTS provided by the discordance in CRL, expressed as the area under ROC curve, was 0.52 (95% confidence interval 0.38-0.67), while it was 0.50 for NT discordance (95% confidence interval 0.35-0.64). NT discordance was significantly higher in sIUGR compared to both uncomplicated and TTTS pregnancies (p=0.004 and p=0.003, respectively).

CONCLUSION

In an unselected population of monochorionic twin pregnancies, discordance in CRL and NT measured during first trimester scan is not a clinically useful predictor of the subsequent development of TTTS. Therefore, strict ultrasound follow up is recommended for the timely diagnosis of TTTS.

Screening for twin-twin transfusion syndrome at 11-14 weeks of pregnancy: the key role of ductus venosus blood flow assessment

OBJECTIVES

A discrepancy in crown-rump length (CRL) and/or nuchal translucency thickness (NT) between monochorionic twins has been found to be associated with an increased risk of twin-twin transfusion syndrome (TTTS). As one of the most plausible mechanisms for increased NT is hemodynamic imbalance and cardiac dysfunction, indirectly manifested by abnormal blood flow in the ductus venosus (DV), we aimed to clarify the role of DV blood flow assessment in identifying those monochorionic twins more prone to develop TTTS.

METHODS

We present 99 cases of monochorionic diamniotic twin pregnancies in which CRL, NT and DV blood flow were evaluated at 11-14 weeks' gestation.

RESULTS

Discrepant values of CRL were not predictive of TTTS development. Intertwin NT discrepancy >or= 0.6 mm had a sensitivity of 50.0% and a specificity of 92.0%. The presence of at least one abnormal blood flow waveform in the DV was associated with a relative risk for developing TTTS of 11.86 (95% CI, 3.05-57.45), with a sensitivity of 75.0% and a specificity of 92.0%. The combination of abnormal DV blood flow with NT discrepancy >or= 0.6 mm yielded a relative risk for the development of TTTS of 21 (95% CI, 5.47-98.33).

CONCLUSIONS

Both intertwin discrepancy in NT and abnormal flow in the DV in monochorionic twins may represent early manifestations of hemodynamic imbalance between donor and recipient. In these pregnancies, in addition to NT measurement at 11-14 weeks, the Doppler assessment of DV blood flow significantly increases the performance of screening for those at risk of developing TTTS.

Prevalence and perinatal outcome of dichorionic and monochorionic twins with nuchal translucency above the 99(th) percentile and normal karyotype

OBJECTIVE

To evaluate the prevalence of and perinatal outcome associated with increased nuchal translucency thickness (NT) > 99(th) percentile in dichorionic and monochorionic twins with normal karyotype.

METHODS

Two hundred and six consecutive twin pregnancies (166 dichorionic and 40 monochorionic) underwent an NT scan during a 4-year period. In those with NT > 99(th) percentile and normal karyotype, we performed first- and second-trimester anomaly scans, fetal echocardiography at 14-16 and 20-22 weeks, maternal serology and, in monochorionic pregnancies, serial ultrasound examinations every other week. Perinatal outcome was recorded.

RESULTS

There were 10 (4.95%) pregnancies in which one of the fetuses had NT > 99(th) percentile and normal karyotype, including five fetuses (1.5%) in dichorionic and five (6.25%) in monochorionic pregnancies. During the same period the prevalence of NT > 99(th) percentile and normal karyotype in singleton pregnancies studied in our center was 2.6%. Among the 10 twins affected, six (60%) were diagnosed with structural abnormalities (three dichorionic and three monochorionic), and two intrauterine fetal demises occurred (one dichorionic and one monochorionic). Thus, the perinatal outcome was normal in only two of the pregnancies, one dichorionic and one monochorionic.

CONCLUSIONS

The prevalence of NT > 99(th) percentile in dichorionic twins with a normal karyotype is similar to that in singletons. In monochorionic twins we confirmed previous studies reporting an increased prevalence compared with singletons. NT > 99(th) percentile with a normal karyotype in twins was associated with a high rate of fetal abnormalities and/or fetal demise (overall 80%) irrespective of chorionicity.

Nuchal translucency and nasal bone in first-trimester ultrasound screening for aneuploidy in multiple pregnancies

OBJECTIVE

To review our experience with first-trimester screening of chromosomal abnormalities in multiple pregnancies using nuchal translucency (NT) thickness measurement and nasal bone assessment.

METHODS

Cases of multiple pregnancy presenting for first-trimester ultrasound evaluation and with viable fetuses measuring between 45 and 84 mm were recruited for this study. Crown-rump length, NT thickness, the presence or absence of the nasal bone and chorionicity were determined and the information prospectively collected in a dedicated database.

RESULTS

There were 206 twin pregnancies, eight sets of triplets, and one set of quadruplets, totalling 440 screened fetuses. Information on perinatal outcome was available in all cases. The NT thickness was measured in all cases and was found to be greater than the 95(th) percentile in six (8.6%) of the 70 monochorionic fetuses and in 10 (2.7%) of the 370 dichorionic fetuses (P < 0.05, Fisher's exact test). The nasal bone was successfully assessed in 421 of the 440 (95.7%) fetuses and found to be absent in only four cases, three of which were found to have aneuploidy. Chromosomal abnormalities were diagnosed in six fetuses from one monochorionic and four dichorionic twin pregnancies. Five of the six affected cases were associated with increased NT thickness (sensitivity 83.3%), whereas the nasal bone was absent in only three of the aneuploid fetuses (sensitivity 50%).

CONCLUSIONS

First-trimester ultrasound screening for chromosomal abnormalities using NT thickness in multiple pregnancies is highly sensitive. However, nasal bone assessment is not only limited in sensitivity but also more challenging in multiple than in singleton pregnancies owing to difficulties in obtaining adequate views of the fetal face.