Nuchal translucency

(**SCROLL DOWN TO THE WORD *NEW* TO SEE THE LATEST POSTINGS OF MEDICAL STUDIES ON NUCHAL TRANSLUCENCY**) 

A measurement is taken of the fluid behind the baby's neck at about 10-12 weeks gestation. In Ultrascreen, it is combined with a blood test from the mother to determine the risk of genetic defect or heart problem. (The blood test measures hormones called PAPP-A and free beta HCG. A PAPP-A measurement that is very low and HCG that is very high can indicate a higher risk of a problem.)

In the vast majority of cases, the baby is healthy. So why the thick fluid behind the neck? Scientists posit that the fluid collects when the heart can't circulate it fast enough, which is to be expected in tiny fetuses just beginning to develop.

This study  shows that scientists are trying to figure out why women get positive Ultrascreen results (signifying their baby is at risk) when the baby is actually healthy.

Here's a great page that explains many terms and shows some charts of risk factors and blood test levels. 

Here's my story:
I went for a routine ultrasound at about 9 weeks to "date the pregnancy." I knew what my dates were, but they were offering, and insurance covered it. I figured, hey, free peek at the baby! It was not done in my doc's office, and the ultrasound tech looked really young. She told us she was concerned by the measurement of the fluid behind the neck. It measured 3.6mm. She sent us for ultrascreen. Meanwhile I googled the topic and was certain my baby would have Down Syndrome or Trisomy 13 or something. At the Ultrascreen, the tech said she didn't see anything that looked like a bad sign. My blood work was fantastic, in the lowest of the risks. (free-hcg - .43 [this is pretty low. High is supposed to be a Trisomy indicator.] PAPP-A - 60th percentile. [Normal]) But they sent the 3.6mm measurement along with the bloodwork to the company that crunches the numbers in their software. I know the tech did not measure that in any of her three measurements, but they are supposed to send the largest one. My risk factor was elevated because of the measurement, which I have since learned is extremely difficult and can be subjective.
I continued to worry, but did not want any invasive tests.
I did agree to the Level II ultrasound and the fetal echocardiogram, which is an ultrasound of the baby's heart. Both found nothing to worry about.
Michael is now eight months old and shows no signs of any problems.
I wish I had never done this test, as it ruined my peaceful feelings about the pregnancy.

The most popular place people have to discuss getting a positive screen result for nuchal translucency (that is, the measurement of the fluid behind the baby's neck that is higher than 3.0mm/3.0 millimeters) is the comments section of babycenter.com
Here is the link:
http://www.babycenter.com/comments/pregnancy/prenatalhealth/118
Many of the posters there are scared and just learning about Ultrascreen and NT. While the Ultrascreen (nuchal translucency measurement plus blood test of the mother for certain markers and hormone levels) is sold as being better than the AFP, this is because it is done earlier in pregnancy. It actually has about the same false positive rate. It does help eliminate some mothers who would have automatically been told to do an amniocentesis in the past. (Those 40 and older, for example.) But it also scares the heck out of young mothers who have to deal with the fear that something could be wrong for almost seven whole months until their baby is born.
 

I will post more links as I find them.

Another study: 

LIMITATIONS OF USING NT TO PREDICT PROBLEMS:

This study points out a fairly big difference in an NT of 2.5mm versus 3.5mm.

This is a nice even-handed scientific explanation that points out only 10% to 15% of babies with increased NT actually have a genetic problem. It states that high NT also indicates a 15% risk of a heart problem. That does not mean 30% of babies with high NT either have a genetic problem or a heart problem. There is some overlap between those two groups. Many babies with a genetic/chromosomal problem, especially Down's Syndrome, also have heart problems. So more than 70% of babies with high NT are healthy and typical at birth and on into childhood.

1) This one shows the NT changes depending on the heartbeat.

2) This study concludes high NT measurements in babies with trisomy may be caused by heart failure. (For those that don't know, heart failure doesn't mean the heart stops. The medical definition is a chronic condition where the heart can't keep up. The symptoms in otherwise healthy adults are shortness of breath and fatigue.) 

NT AND CORD AROUND NECK:
This study says when the cord is around the neck (called nuchal cord) this can cause an increased NT in a baby who has no problems and will be born normally. So if the cord is seen around the neck, coupled with high NT, this should be reassuring to the patient, because the "nuchal cord" is a likely cause of high NT.

NT AND WHAT DOCTORS STILL DON'T UNDERSTAND: This study states upfront: The ultrasonographic measurement of nuchal translucency thickness at 10-13 weeks of gestation is accepted as an efficient method of screening for chromosomal abnormalities. However, the underlying mechanism producing increased nuchal translucency thickness is still poorly understood. In the study of 65 fetuses, 17 had high NT measurement. Five of those turned out to have chromosomal abnormalities.

NASAL BONE: This study shows the absence of the nasal bone is an independent factor that should be considered, and can't be predicted simply using the PAPP-A and free HCG blood test.

This abstract from a 2003 study shows that looking for the nasal bone has a lower false positive rate than using NT.  

DWARFISM: This study follows one expectant mother who had a normal CVS test after a high NT. A later ultrasound found skeletal evidence of dwarfism. A DNA test was done confirming this.

OUTCOMES FOR HIGH NT CHILDREN:

This study's abstract states that if there is increased NT but the CVS or amnio is clear and the 20-22 week ultrasound is normal, "the risk of an adverse perinatal outcome and postnatal developmental delay is not statistically increased" over those with a normal NT!

 This study (FULL TEXT PDF!) published in 2007 followed children who had increased NT (greater than 3.5mm) but looked normal on their ultrasounds. The study found those children were not at greater risk for developmental delays at age 2. "Counseling should emphasize that when the karyotype is normal and no fetal structural malformation was missed prenatally after resolution of nuchal thickening, the prognosis is not impaired at the age of 2 years."

ANXIETY AND PREGNANCY

At least all your worrying isn't hurting the baby, according to this study released this month. (Abstract)

**NEW**

NT AND MATERNAL AGE

This study abstract shows the Ultrascreen (NT, blood tests, etc) is much more accurate than using maternal age alone. However the mother's age is usually factored into the formula at most labs. They take the NT measurement, the blood test results and maternal age and put them in a computer formula to give you your new risk result. This is the ratio you receive as your screening "result." It is just a risk factor, not a diagnosis. Doctors usually compare this risk factor to the general risk calculated by maternal age alone. If your risk is greater than normal for your age, usually you will be referred for follow up testing. If your risk factor is lower than normal for your age, you will usually be told everything is likely to be OK because the test shows you have a decreased risk for problems compared to other mothers your age.

NT instant results

In some practices, women are being given the Ultrascreen dried blood sample card at home to mail in prior to the test. After the ultrasound, instant results are given. Instant results have correlated with an increase in CVS rates. (Probably because more people know they want to have CVS before it is too late for the test.) See abstract here.