Monica Flessel, PhD, and Sara Goldman, MPH, Genetic Disease Screening Program, California Department of Public Health
The California Department of Public Health’s Prenatal Screening Program (PNS) will begin incorporating noninvasive prenatal testing (NIPT) by November 2013. Noninvasive prenatal testing uses cell-free fetal DNA from the plasma of pregnant women and offers tremendous potential as a screening tool for fetal aneuploidy.
PNS currently offers three types of screening tests to pregnant women to identify individuals who are at increased risk for carrying a fetus with a specific birth defect: quad marker screening, serum integrated screening, and sequential integrated screening, which includes a first-trimester preliminary risk assessment for Down syndrome and trisomy 18 if a nuchal translucency ultrasound is performed.
If a maternal serum screening test result is reported as screen positive, indicating an elevated risk for a chromosomal anomaly or birth defect, genetic counseling and other follow-up services are provided free of charge at state-approved prenatal diagnosis centers (PDCs).
PNS plans to offer NIPT through PDCs as an option for all women who screen positive for Down syndrome, trisomy 18, or a large nuchal translucency measurement following biochemical screening. These women will also retain the option of proceeding directly to a diagnostic test, such as chorionic villus sampling or amniocentesis. If an NIPT result is negative, no diagnostic tests or further follow-up services will be authorized. Women with a negative NIPT result in the first trimester will remain eligible for biochemical serum screening in the second trimester, with all analyte values reported. However, only a risk assessment for neural tube defects (NTDs) and Smith-Lemli-Opitz syndrome (SLOS) will be reported.
Women with a positive NIPT result will be authorized to receive confirmatory diagnostic tests and other follow-up services. They will also remain eligible for biochemical serum screening in the second trimester for a risk assessment for NTDs and SLOS. Women who are drawn for NIPT outside of PNS will not be eligible for PDC follow-up services through the program.
Changes planned for September 2013
Fetuses with a large nuchal translucency measurement (greater than or equal to 3.5 mm) are reported to have more than a 20% risk for a chromosomal abnormality. These fetuses are also at risk for congenital heart defects. ACOG guidelines recommend a targeted ultrasound, fetal echocardiogram, or both for patients with a large nuchal translucency measurement. The inclusion of fetal echocardiogram for patients with a large nuchal translucency measurement has been problematic for PNS. Not all PDCs have offered this service, and the timeframe for a fetal echocardiogram makes these cases difficult for PNS and PDC staff to track.
As of September 2013, PNS no longer authorizes a fetal echocardiogram for patients with a large nuchal translucency measurement. These patients need to be referred to pediatric cardiologists using their own insurance.
In addition, PNS no longer reimburses patients for amniotic fluid alpha-fetoprotein and acetylcholinesterase analysis, unless the PNS result indicates an increased risk for NTDs. For patients who screen negative for NTDs, almost 99% have negative alpha-fetoprotein and acetylcholinesterase results following amniocentesis, including the majority of NTD cases for this group, which are identified primarily by ultrasound findings.