Early Risk Assessment

Is there a way to obtain risk assessment earlier in pregnancy?Yes. We call this ERA which stands for Early Risk Assessment. ERA is performed between 11.5-14 weeks and involves an ultrasound to measure the nuchal translucency (the fluid in the back of the neck of the fetus). At the same time, a maternal blood sample is obtained. Based on a combination of the mother’s age, the size of the nuchal translucency and the levels of the two proteins (free beta hCG and PAPP-A) in maternal blood, the probability for Down syndrome is calculated, similar to second trimester risk assessment. ERA is followed by an ultrasound after 16 weeks to look for structural abnormalities

The nuchal translucency is typically very tiny, only 1 to 2 mm. It takes special training and expertise to make this measurement accurately. The Fetal Medicine Foundation has played a leading role in standardizing the precise way this measurement should be made and interpreted. They provide certification to those who have had additional training, have demonstrated the ability to make this measurement to their satisfaction, and submit their data on a regular basis for ongoing analysis and quality review. We feel that only when the nuchal translucency is measured by someone with Certification by the Fetal Medicine Foundation can you be confident that the calculated risk of Down syndrome is accurate.

How does ERA compare to second trimester risk assessment? Since ERA is earlier than second trimester risk assessment, and most women get reassuring news, they will be reassured several weeks earlier. Women who choose to have an amnio can have it done at 15 weeks, the same gestational age as those who go directly to amnio. We think ERA provides an estimate of risk of both Down syndrome and other chromosome abnormalities that is a bit more accurate than either the triple screen or the quad screen. Finally, measurement of nuchal translucency will occasionally provide an indication of a structural or genetic problem.

Can you combine ERA with second trimester risk assessment?This is a very complex issue. To do this properly, we would have to withhold the information from ERA until after the second trimester screening results are back. This defeats the major advantage of ERA, earlier diagnosis. Therefore, we recommend that women who choose ERA do not have second trimester serum screening.

Occasionally there are findings on the ultrasound done after 16 weeks that make us reconsider the need for amniocentesis.

What are the drawbacks of ERA? They include the drawbacks of second trimester risk assessment: only after an amniocentesis can we be certain that the fetus does not have Down syndrome or any other chromosomal abnormality. In addition, second trimester risk assessment has been in use longer in the United States, and is considered the “standard of care” by the American College of Obstetricians and Gynecologists. Although ERA is somewhat newer, it has been used for several years in Europe, and recent American studies have confirmed the European experience. ERA requires registration for prenatal care prior to 14 weeks. Some people are concerned about the cost of additional ultrasounds, and that sufficient expertise for measurement of the nuchal translucency is not widely available.

ERA does not screen for many structural abnormalities, including spina bifida. Therefore, we urge all women who have been screened by ERA to have a second trimester structural survey after 16 weeks. We feel that this makes serum AFP screening for abnormalities like spina bifida unnecessary. Although there are some birth defects that can be detected by second trimester AFP screening but be missed by ultrasound, these are exceedingly uncommon