Recipient(s) will receive an email with a link to 'Second-Trimester Screening (Maternal Serum Screening; Quad Screen)' and will have access to the topic for 7 days.
Subject: Second-Trimester Screening (Maternal Serum Screening; Quad Screen)
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Performed between 15 and 22 weeks of gestation, the quadruple screen combines maternal age plus four serum biochemical markers: hCG, inhibin A, AFP, and unconjugated estriol to assess the risk of trisomy 21 and trisomy 18.
Risk assessment for trisomy 21 (Down syndrome), trisomy 18, and open neural tube defects.
Trisomy 21 profile typically has high levels of hCG and inhibin A with low levels of AFP and unconjugated estriol.
Trisomy 18 is associated with low levels of hCG, AFP, and estriol. (Inhibin A does not contribute to trisomy 18 risk profile.)
Different centers use different cutoffs, balancing detection rate against number of invasive procedures performed. A cutoff of 1:270 (approximately 5% positive screening rate) detects approximately 80% of trisomy 21 and trisomy 18 pregnancies.
Detects fewer affected pregnancies than combined first-semester plus second-trimester screening modalities.
Does not permit first-trimester decision making regarding termination of affected pregnancies.