Maternal Serum Screening
Down Syndrome, Trisomy 18 and Neural Tube Defects
Published: March 2011
Hot Topic Q&A is an opportunity for viewers to submit questions to the Hot Topic presenter. The opportunity to submit questions for this topic is now closed.
The following questions were submitted by viewers and answered by the presenter, Alicia Algeciras-Schimnich, PhD, Assistant Professor of Laboratory Medicine and Pathology and Director of the Automated Immunoassay Laboratory in the Division of Clinical Biochemistry & Immunology at Mayo Clinic. Questions are presented as submitted (unedited).
I wonder why in vitro fertilization (IVF) is one of the reasons the test would have to be weighted differently. What effect does this have compared to ethnic, diabetes, etc.? How does IVF affect the prenatal screening tests?
In IVF pregnancies, estriol and PAPP-A values are on average lower and hCG is higher. If not taken into account by adjusting these values, the positive rate will be elevated. Another important factor is whether or not a donor egg was used. If a donor egg is used, the donor’s date of birth or age needs to be supplied to ensure accurate risk assessment.
What are the ages of women with high-risk pregnancies?
With regard to maternal age, each woman has her own perception as to what she feels is a high risk. The risk for Down syndrome does increase with age as shown in table below. The age related risk is incorporated with risk factors derived from the ultrasound and biochemical markers. It should also be noted that the detection rate and positive rate increase with age.
Age at expected
date of delivery (years)Risk at term151/1516161/1512171/1508181/1502191/1494201/1484211/1470221/1452231/1430241/1400251/1362261/1315271/1255281/1182291/1095301/994311/881321/759331/634341/513351/403361/308371/231381/172391/129401/98411/76421/61431/50441/43451/38461/34471/31481/29491/28501/27511/26521/25531/25541/25551/24