It is usually part of an assessment called combined first trimester screening. Combined first trimester screening Combined first trimester screening assesses the risk for your baby having certain chromosomal abnormalities trisomy 13, 18 and This testing combines the nuchal translucency ultrasound with specific blood tests. Nuchal translucency ultrasound alone can also provide this risk assessment, but it is not as accurate as combined first trimester screening.
Accuracy of Transvaginal Ultrasound for Dating Pregnancy
Ultrasound: Sonogram - American Pregnancy Association
American Institute of Ultrasound in Medicine consensus report on potential bioeffects of diagnostic ultrasound. National Council on Radiation Protection and Measurements. Criteria Based on All Known Mechanisms. National Council on Radiation Protection and Measurements; Effective prenatal diagnosis relies on a high standard of imaging. Several national and international bodies have described standards for imaging in the first, second, and third trimester of pregnancy. However, many experts in the field advocate the use of additional views to improve diagnostic performance.
First Trimester / Dating Ultrasound
First trimester ultrasound is performed in the first months of a pregnancy. Pregnancy ultrasounds are performed mainly using transabdominal ultrasound. For many women, especially after 8 weeks gestation, sufficient information about the baby may be obtained with transabdominal ultrasound only. However, in the early pregnancy, the developing embryo is very small at 6 weeks gestation, the baby is only mm long and a transvaginal ultrasound may be required to get a better image of the baby. Transvaginal ultrasound is safe and commonly performed during all stages of pregnancy, including the first trimester.
Underestimation of gestational age by conventional crown-rump length growth curves. Reprinted with permission of American College of Obstetricians and Gynecologists Variations in the measurement of CRL can be attributed to differences in fetal growth patterns. Such differences are related to factors similar to those that influence birth weight curves, including maternal age and parity, prepregnancy maternal weight, geographic location, and population characteristics.