When it comes to genetic screening for fetal abnormalities, there are many choices available and choosing the right test can be complicated. Most testing is non invasive and can have a high accuracy rate for identifying chromosomal abnormalities and birth defects. It is important to understand that comprehensive fetal screening is most accurate when it includes both maternal blood testing combined with ultrasound. The right blood test to choose and the timing of ultrasound will vary.
For most low risk women, First trimester ultrasound evaluation with Nuchal translucency, and nasal bone assessment combined with the free beta HCG and PAPP A blood testing is sufficient. This combined test will identify 85-90 % of the most common chromosomal abnormalities and severe birth defects at an early gestational age. If an abnormality is identified, then further testing is provided.
In women who are high risk such as women over the age of 35, combining circulating cell free DNA with First trimester ultrasound evaluation and Nuchal translucency and nasal bone assessment will identify > 90% of the most common chromosomal abnormalities and severe birth defects. Including the PAPP A blood test also identifies women who are at risk for preeclampsia, small for gestational age babies, and increased risks of placental dysfunction and preterm delivery. An abnormal result can then be evaluated with further testing.
Choosing the right test is complex, however combining ultrasound imaging with a maternal blood test will provide the most comprehensive testing. Earlier diagnosis is always better for pregnancy planning.
Low risk women – First trimester ultrasound and nuchal translucency/nasal bone with free beta HCG and PAPP A. Optional would be the circulating cell free DNA. PAPP A should be included in patients with additional risk factors.
High risk women – First trimester ultrasound and nuchal translucency/nasal bone with circulating cell free DNA and PAPP A.