Maternal Serum Screening
Down Syndrome, Trisomy 18 and Neural Tube Defects
Second Trimester Screening
March 2011
Second trimester screening is performed between 15 and 22 weeks of gestation.
The biochemical markers used to derive a risk estimate are: alpha-fetoprotein or AFP, unconjugated estriol or ue3, hCG and inhibin A. AFP is used on the risk calculation of the all 3 conditions. Low levels of AFP are seen in Down syndrome and trisomy18 pregnancies, whereas increases are seen in neural tube defects. Unconjugated estriol, an estrogen produced by the placenta, is decreased in the majority of Down syndrome or trisomy 18 pregnancies. hCG is normally increased in Down syndrome pregnancies and decreased in trisomy 18 pregnancies. Inhibin A is only used to calculate the risk for Down syndrome, as in these cases it tends to be elevated.
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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