Prenatal screening for Down syndrome and other birth defects has for decades been an anxious rite of passage for many pregnant women. For many, especially those over 35, the joy of finding out they are pregnant is tempered by weeks of anxiety as they await the fourth month of their pregnancy for the tests to be done.
Not anymore. For the first time since such prenatal chromosome screening was introduced in 1990, women of any age can choose to have screening tests done 11 to 13 weeks into their pregnancy. Not only does that cut down on the waiting time, but the newer tests are better than the older ones at predicting the likelihood that a fetus has some of the most common and serious chromosomal abnormalities.
This story discusses first trimester screening for prenatal chromosomal abnormalities, namely Down syndrome. A study in the New England Journal of Medicine (NEJM) looked at sequential screening of women 10-13 weeks into their pregnancy, instead of the typical 16 week screening. Combining blood tests and ultrasound screening succeeded in finding 87% of Down fetuses (though a positive test is still only a prediction of increased risk that a baby will be born with Down syndrome). The journalist did not mention the false positive rate of the 1st trimester vs. 2nd trimester screenings in the NEJM study, nor the study design. However, a discussion of what constitutes a “positive” result of screening was a plus for this story. The story also was balanced in presenting the risks of screening and the risk of miscarriage due to subsequent diagnostic tests, such as chorionic villus sampling or CVS (sampling cells via a thin tube or needle inserted into the placenta) and amniocentesis. There was no discussion of the cost of these tests earlier in the
No information about the cost
of the screening or diagnostic tests, either alone or in combination. No information if both forms of testing in first
trimester are covered by insurance.
Not much quantitative data presented.
Mentions harms of miscarriage with the
CVS testing and amniocentesis. Briefly mentions psychological harm of screening if you do not want to go through with more
risky diagnostic tests–more anxiety during the pregnancy if you have a positive Down result in screening.
No mention of study design, although
discussion of design in this case (sequential treatment for all participants vs. randomization to control and treatment
groups) was not crucial to interpreting results of the study. No mention of false positive rate. (About 5% with first
trimester combined screening.)
Frames risk factors of more invasive diagnostic tests and the
risk of screening (in terms of anxiety if you choose not to have the further tests).
Potential conflict of interest is not discussed, but there are a number of local experts in
ob/gyn quoted, however no patients. Nobody cited affiliated with the New England Journal of Medicine study, upon which the
story is based.
Mentions alternatives of second trimester testing or no screening at all, but seems to promote the
screening. Gives estimate of miscarriage with diagnostic tests.
Story address the
greater demand for 1st trimester testing, but does not address availability in smaller hospitals, nor is there a discussion
that there is specialized training and a certification process for nunchal translucency (the ultrasound test) for both
sonographers and physicians.
Mentions that combination of
screening methods provide greater accuracy sooner in pregnancy. Neither is a “new’ test, however.