THE TRIPLE SCREEN

The triple screen is a blood test typically performed between 15 and 20 weeks of pregnancy to detect women whose pregnancies may be at higher risk for open neural tube defects (such as spina bifida, an opening in the spine); Down syndrome and trisomy 18

The triple screen measures the levels of three chemicals in the mother’s blood; two (estriol and hCG) are hormones produced by the placenta, and the other is alpha fetoprotein (AFP), a protein made in the baby’s liver and secreted into the amniotic fluid surrounding the baby.  All three chemicals cross the placenta and enter the mother’s bloodstream, where they can be measured. 

Chromosomes are the inherited structures in the cells of our bodies. There are 46 chromosomes in each cell, arranged into 23 pairs. Chromosome abnormalities involving a missing or extra chromosome are not inherited or caused by an exposure during pregnancy. Instead, they result from a chance mistake in cell division at the time of conception.  This error is a random event that can occur in anyone's pregnancy.

Because an abnormal triple screen may indicate an increased risk for Down syndrome or other abnormalities in the baby, there is the option for diagnostic testing by amniocentesis.

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