Given the theoretical risk of thermal damage to the developing fetus from the use of color and pulsed Doppler US, its use is not advised when the nuchal translucency is of normal thickness or below the threshold of 3 mm at 11 to 14 weeks of gestation [2,19]. US Echocardiography Fetal In the absence of other maternal or fetal risk factors, there is no literature to support the routine use of fetal echocardiography in patients with normal nuchal translucency measurements at 11 to 14 weeks of gestation [20]. US Pregnant Uterus Transabdominal ACOG recommends aneuploidy screening or diagnostic testing be offered to all women in early pregnancy [2]. For women who choose screening over invasive diagnostic testing, first trimester combined screening with nuchal translucency and maternal serum markers remains a reasonable option for single and twin gestations [2,18,21]. Although ACOG does not endorse a specific screening test, citing that no one screening test is superior to another in all test characteristics, there are several benefits of first trimester screening, including maternal privacy, early reassurance, and timely detection of fetal abnormalities with the option for earlier and safer pregnancy termination [2]. Using the nuchal translucency measurement and maternal serum pregnancy-associated plasma protein A and free beta subunit of human chorionic gonadotropin levels, most laboratories will report specific risk estimates for trisomy 21, 18, and 13 after adjusting for crown-rump length and maternal factors such as age, prior history of aneuploidy, weight, and race [2]. In clinical practice, first trimester combined screening for aneuploidy detects about 90% of affected pregnancies at a false positive rate of 5% for single gestations with slightly lower sensitivities reported for twins [12,17].
Nuchal Translucency Evaluation at 11 to 14 Weeks Gestational Age. Given the theoretical risk of thermal damage to the developing fetus from the use of color and pulsed Doppler US, its use is not advised when the nuchal translucency is of normal thickness or below the threshold of 3 mm at 11 to 14 weeks of gestation [2,19]. US Echocardiography Fetal In the absence of other maternal or fetal risk factors, there is no literature to support the routine use of fetal echocardiography in patients with normal nuchal translucency measurements at 11 to 14 weeks of gestation [20]. US Pregnant Uterus Transabdominal ACOG recommends aneuploidy screening or diagnostic testing be offered to all women in early pregnancy [2]. For women who choose screening over invasive diagnostic testing, first trimester combined screening with nuchal translucency and maternal serum markers remains a reasonable option for single and twin gestations [2,18,21]. Although ACOG does not endorse a specific screening test, citing that no one screening test is superior to another in all test characteristics, there are several benefits of first trimester screening, including maternal privacy, early reassurance, and timely detection of fetal abnormalities with the option for earlier and safer pregnancy termination [2]. Using the nuchal translucency measurement and maternal serum pregnancy-associated plasma protein A and free beta subunit of human chorionic gonadotropin levels, most laboratories will report specific risk estimates for trisomy 21, 18, and 13 after adjusting for crown-rump length and maternal factors such as age, prior history of aneuploidy, weight, and race [2]. In clinical practice, first trimester combined screening for aneuploidy detects about 90% of affected pregnancies at a false positive rate of 5% for single gestations with slightly lower sensitivities reported for twins [12,17].