However, high resolution transvaginal US may more clearly identify the amnion and nuchal translucency borders to ensure an accurate maximal measurement in patients with suboptimal transabdominal views. US Echocardiography Fetal An increased nuchal translucency in a dichorionic twin is an indication to obtain a fetal echocardiogram [20]. Performing fetal echocardiography on twins is challenging because of both maternal factors, such as increased body mass index or inability to rest comfortably during a lengthy examination, and fetal factors, such as unfavorable fetal position or limited views due to the presence of a co-twin. Although early fetal echocardiography may be attempted, a standard fetal echocardiogram at 18 to 22 weeks with an expected detection rate of over 80% for major cardiac anomalies is recommended when increased nuchal translucency is detected in dichorionic twins [26,44]. One of the advantages of nuchal translucency screening in dichorionic twins is the ability to perform individual measurements on each fetus and generate fetus-specific risks [45]. The management of a positive screen or an increased nuchal translucency is similar in twins and singletons; genetic counseling, diagnostic testing, and in continuing pregnancies with a history of increased nuchal translucency or diagnosed with fetal aneuploidy, a detailed anatomic survey, and fetal echocardiography in the second trimester are recommended. The prevalence of increased nuchal translucency in dichorionic twins with a normal karyotype is similar to that in singletons [56]. Although an individual risk can be estimated for each twin and a patient may opt for only sampling the twin suspected to be at risk, it is customary to sample both twins at the time of diagnostic testing to avoid a missed diagnosis because of averaged maternal biochemistries or incorrect assignment of chorionicity [57].
Nuchal Translucency Evaluation at 11 to 14 Weeks Gestational Age. However, high resolution transvaginal US may more clearly identify the amnion and nuchal translucency borders to ensure an accurate maximal measurement in patients with suboptimal transabdominal views. US Echocardiography Fetal An increased nuchal translucency in a dichorionic twin is an indication to obtain a fetal echocardiogram [20]. Performing fetal echocardiography on twins is challenging because of both maternal factors, such as increased body mass index or inability to rest comfortably during a lengthy examination, and fetal factors, such as unfavorable fetal position or limited views due to the presence of a co-twin. Although early fetal echocardiography may be attempted, a standard fetal echocardiogram at 18 to 22 weeks with an expected detection rate of over 80% for major cardiac anomalies is recommended when increased nuchal translucency is detected in dichorionic twins [26,44]. One of the advantages of nuchal translucency screening in dichorionic twins is the ability to perform individual measurements on each fetus and generate fetus-specific risks [45]. The management of a positive screen or an increased nuchal translucency is similar in twins and singletons; genetic counseling, diagnostic testing, and in continuing pregnancies with a history of increased nuchal translucency or diagnosed with fetal aneuploidy, a detailed anatomic survey, and fetal echocardiography in the second trimester are recommended. The prevalence of increased nuchal translucency in dichorionic twins with a normal karyotype is similar to that in singletons [56]. Although an individual risk can be estimated for each twin and a patient may opt for only sampling the twin suspected to be at risk, it is customary to sample both twins at the time of diagnostic testing to avoid a missed diagnosis because of averaged maternal biochemistries or incorrect assignment of chorionicity [57].