Maternal Serum Screening
Down Syndrome, Trisomy 18 and Neural Tube Defects
Second Trimester Screening
March 2011
In contrast to first trimester screening, second trimester screening provides risk estimates for Down syndrome, trisomy 18 and also neural tube defects. For Down syndrome, a screen-positive or negative interpretation and a numeric risk is provided based on the cut-off of equal or higher than 1 in 270. Using this cutoff, the detection rate for Down syndrome is approximately 81% and the false-positive rate is approximately 5%. For trisomy 18, risk estimates of 1 in 100 or higher are reported as screen positives. The detection rate for trisomy 18 is 80% with a false-positive rate of less than 1% for the second trimester screening. For neural tube defects, only alpha-fetoprotein is used for the risk assessment. An AFP multiple of the median (or MOM) equal to or higher than 2.5 is reported as screen positive. Second trimester screening has a detection rate for neural tube defect of approximately 80% with a false-positive rate of 1% to 3%.
Second Trimester Screening |
Jump to section:
- Introduction
- What is Maternal Serum Screening?
- Who Should Be Offered Maternal Serum Screening?
- Maternal Serum Screening: Options
- Maternal Serum Screening: Risk Calculation
- First Trimester Serum Screening
- Nuchal Translucency (NT)
- Nuchal Translucency (NT)
- Nuchal Translucency (NT)
- First Trimester Serum Screening
- First Trimester Screening
- Second Trimester Screening
- Second Trimester Screening
- Second Trimester Screening
- Sequential Screening
- Sequential Screening
- Sequential Screening
- Sequential Screening
- Mayo Medical Laboratories Maternal Serum Screening Options
- References
- Questions?
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