First-Trimester Screening with Instant Risk Assessment.

Is second-trimester screening
accurate enough?

Standard second-trimester blood tests for chromosomal abnormalities result in false-positive results in 6% to 10% of women under age 35 and 20% to 30% of women over age 35. Positive findings lead some women to invasive testing, which comes with risks. False positives therefore lead to unnecessary invasive testing... and unnecessary risk.

Milestones in the accuracy
of screening for birth defects.

In 1992, nuchal translucency (NT) — the fluid accumulation at the back of the fetal neck — at 11 weeks to 13 weeks 6 days was shown to be a strong marker for Down syndrome, trisomy 18 and other chromosomal abnormalities. Around the same time, PAPP-A and freeBeta-hCG were found to be the most sensitive and specific biochemical markers for Down syndrome and trisomy 18 and 13. Then, in 2002, absent or hypoplastic nasal bones (NB) were found to be another possible marker for chromosomal and other abnormalities.

Combining methods for
maximum screening accuracy.

Combined evaluation of NT, NB, PAPP-A and freeBeta-hCG between 11 weeks 0 days and 13 weeks 6 days provides the highest detection rates — and lowest false-positive rates — for Down syndrome and trisomies 13 and 18. Using this combined method, 91% of Down syndrome pregnancies and 98% of trisomy 13/18 pregnancies can be detected. In women younger than age 35 at delivery, the false-positive rate is 3% to 5%. For women who are age 35 or older at delivery, the false-positive rate is 5%.

Neural tube defects are not detected by first-trimester screening, so it’s important to follow up with maternal serum AFP screening and/or high-resolution ultrasound examination in the second trimester.

The only source for early
& instant risk assessment.

First-trimester screening with instant risk assessment occurs between 11 weeks and 13 weeks 6 days. However, the blood samples (PAPP-A and FreeBeta-hCG), can be obtained by the patient — in the convenience of her home — as early as 9 weeks 0 days. We can provide a kit with all the necessary materials, including a postage-paid mailer, so the patient can send the sample to the lab in advance of her ultrasound. In week 11, 12 and 13, ultrasound NT and NB measurements are entered into a computer, and the risks for Down syndrome and trisomies 13 and 18 are generated instantly. In Nevada, Center for Maternal Fetal Medicine is the only group to have all its doctors certified for ultrasound using this technique.