ROC offers a variety of technical services including ultrasound examinations, fetal monitoring, amniocentesis, chorionic villus sampling (CVS), fetal blood sampling and first and second trimester screening.

Our state-of-the-art ultrasound equipment and experienced staff allow more detailed ultrasound experiences. 

CVS and amniocentesis enable the unborn baby's chromosomes to be studied to detect Down syndrome or other chromosomal abnormalities. Other genetic testing can be performed by CVS or amniocentesis as indicated. CVS is performed between 10 and 12 weeks gestation. Amniocentesis is typically performed between 15 and 18 weeks gestation.


First trimester screening is performed between 11 and 13 weeks gestation. This screening involves a specialized ultrasound and a blood test. The screen is used to detect an increased risk for Down syndrome, Trisomy 13 and Trisomy 18. These three conditions are chromosomal abnormalities that can result in varying degrees of mental retardation and birth defects for a developing baby.

Traditionally screening for Down syndrome and Trisomy 18 has been done in the second trimester (15-20 weeks gestation). First trimester screening can be done as early as 11 weeks and 1 day gestation, counting from the first day of the woman's last menstrual period, through 13 weeks and 6 days.

With ultrasound, a special measurement, called nuchal translucency, is taken. This is a measurement at the back of the baby's neck.  With ultrasound the sonographer also attempts to see the nasal bone.   Blood work is also done. Two chemicals, free beta hCG and PAPP-A are measured in the woman's blood. The ultrasound measurements, blood work and the woman's age are combined to create her personalized risk to have a baby with Down syndrome, Trisomy 18 and Trisomy 13. The result of the screening test is usually available within one week.

Screening cannot determine if the baby has Down syndrome, Trisomy 13, or Trisomy 18. It can only give an estimate of risk such as 1 in 100. First trimester screening has a detection rate of 90% or greater. This means that not all babies with these conditions will test positive on the screen. Thus a normal result does not guarantee that the baby does not have one of the three conditions. The only way to know for sure if a baby has one of these chromosome abnormalities is to have a diagnostic test such as CVS or amniocentesis.

Having this screening in the first trimester can provide a woman with earlier reassurance that her pregnancy is not at increased risk. If the pregnancy is at increased risk, finding out earlier gives the woman the option of having a diagnostic test to find out with greater than 99% accuracy if the baby has the condition. Knowing the baby has Down syndrome, Trisomy 13 or Trisomy 18 allows better management of the pregnancy between the patient and her doctor, facilitating a healthier outcome.

Ultrasound technologists must have special certification to perform first trimester screening.  Because first trimester screening is done so early in pregnancy, women need to know about its availability so that they will be sure to see their obstetrician in time have or be refererred for the testing. If you are interested in first trimester screening and are currently pregnant, please ask your doctor about this testing.

Second trimester screening is typically performed between 15 and 18 weeks of gestation. This screening also is used to detect an increased risk for Down syndrome and Trisomy 18. However, the detection rate is not as high as with first trimester screening. Second trimester screening can also detect an increased risk for open spine defects such as spina bifida.

Non-invasive fetal monitoring is performed as part of a comprehensive biophysical profile assessment. Fetal monitoring is indicated in the third trimester to assess fetal well-being in women with high-risk factors.


Regional Obstetrical Consultants serving mothers and babies throughout Southeast Tenn, North GA and Western NC.
902 McCallie Avenue, Chattanooga, TN
(423) 664-4460 | (866) 4HI-RISK