Working with Mother and Doctor for a Healthy Delivery

First Trimester Screen (Sequential screen)

  • Sequential Screening is a way to estimate the chance that a baby will be born with Down syndrome, trisomy 18, or an open neural tube defect such as spina bifida. It combines measurements from two blood tests and a first trimester ultrasound, along with other details about you, to give you a more specific risk. Screening tests do not diagnose or rule out any specific condition, they only give you better information about your baby’s risk for having a chromosomal problem.
  • Sequential Screening is a two-step process; however, if you are at higher risk for Down syndrome or trisomy 18, you will be notified after the first blood test. 
  • The screening test does not detect neural tube defects; however you will be offered a Serum AFP test in the second trimester for this purpose. 
  • The first trimester screen has been available in the U.S. for several years, and recently has been determined to be an effective means of early chromosomal abnormality screening. 
  • It is important to know that the first step of this test must be performed between the 11th and 13th week, to allow measurement of the fluid-filled space at the back of the baby's neck, which is called the nuchal translucency. If this measurement cannot be taken, you may need to come back another time. If you cannot come back within the appropriate timeline, the two blood tests can still provide helpful information. 
  • All of our doctors and sonographers are credentialed by the Nuchal Translucency Quality Review Program ( 
  •  “A Positive Test” only means that your pregnancy is at an increased risk for Down syndrome or trisomy 18. It does NOT mean that the baby has a chromosome problem. Your doctor at RPG will discuss your option of diagnostic testing to help determine whether or not the baby has a chromosome abnormality. 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
Willis Knighton Health