You can have an ultrasound and a blood test organized by your health-care practitioner. The following steps can be followed:
- Get a 11-14 week (nuchal translucency) ultrasound in the first trimester of pregnancy (when you are about 3 months pregnant). There should be no prenatal screening blood work done on the day of this ultrasound. The "Multiple Marker Screening" requisition form will be filled out at the time of the ultrasound. It is important that you keep this requisition in a safe place because it will be needed for blood work later in the pregnancy.
- Go for Second Trimester Screening (STS) blood work in the second trimester (when you are about 4 or 5 months pregnant). You must wait until at least 8 weeks have passed from the miscarriage of the twin.
Download Step-by-Step Instructions
How does the screening work?
This screening test will combine all the information below to tell you about the chance to have a baby with trisomy 21 and trisomy 18:
| Your age at the time of birth
You have a higher chance for chromosome differences like trisomy 21 and trisomy 18 as you get older. If you got pregnant through in vitro fertilization, it is the age of the egg that is used. The egg may be your own or from a donor.
| 11-14 week (nuchal translucency) ultrasound result
The nuchal translucency (NT) refers to the pocket of fluid at the back of the baby's neck. This pocket of fluid is measured during the ultrasound. When there is more fluid than what we typically see, there is an increased chance for trisomy 21, trisomy 18 and other conditions.
| Blood draw result
The blood test for STS will measure the amount of 4 proteins made by your pregnancy.
| Other information about you
Your health-care practitioner will ask you some questions about you that improve the accuracy of test. You will be asked about your racial identity, diabetes status, smoking history in the pregnancy, weight and whether the pregnancy happened through in vitro fertilization.
How long does it take to get results?
The results will be shared with your health-care practitioner within about 5 working days after your blood work. Keep in mind that your practitioner may not get the report right away. Talk to your practitioner about how they plan to give you these results.
What type of results will I get?
When you get your report, it will most likely say that you have a “screen negative” result. This means that you have a lower chance to have a baby with trisomy 21 and trisomy 18. It does not mean "no chance".
Some individuals will get a “screen positive” result, which means that there is a higher chance to have a baby with trisomy 21 or trisomy 18. It does not mean your baby definitely has one of these chromosome differences. You would have more options for testing, including diagnostic testing.
