The test uses a combination of a maternal blood test and an ultrasound of your baby. The ultrasound measures the thickness of the skin at the back of your baby’s neck, called the nuchal fold (see Nuchal translucency screening). The blood test looks at the levels of two chemicals: pregnancy associated plasma protein A (PAPP-A) and one of the pregnancy hormones, human chorionic gonadotrophin (hCG). The results of the blood test is combined with your age, and the measurement of the nuchal fold. A mathematical formula is then used to calculate your baby’s risk of Down syndrome. If you have your blood test before your ultrasound, you will usually receive your results immediately following your ultrasound. If you have your blood drawn at the time of the ultrasound you will receive your results a few days later. Your risk based on the combined test may be higher than your risk based on your age alone, lower, or stay the same.
