Should i do first trimester screening

Then he or she gently moves a hand-held device called a transducer over your belly. Images of the baby are displayed on a monitor. The doctor can look for and measure the thickness at the back of the baby's neck. A simple blood test is all that's needed for the rest of the first-trimester screening. The health professional taking a sample of your blood will:. There are no known physical risks to having the tests, other than a possible bruise on your arm from the blood test.

The doctor looks at the test results—along with your age and other factors—to find out the chance that your baby may have certain problems. A screening test shows the chance that a baby has a certain birth defect. The accuracy of a screening test is based on how often the test correctly finds a birth defect. It's possible that a screening test will be positive—meaning the test result is abnormal—but the baby doesn't have the problem.

This is called a false-positive test result. And it's also possible that a screening may show that a baby doesn't have a birth defect when he or she does have it. This is called a false-negative test result. A false-positive result can cause stress and lead to unnecessary testing such as chorionic villus sampling [CVS].

Many women who have a positive screening test result are actually carrying a healthy baby. A "positive" result means that there is a higher-than-average chance your baby has Down syndrome or trisomy If the result is "negative," it means that your baby probably doesn't have those birth defects.

But it doesn't guarantee that you will have a normal pregnancy or baby. Your doctor may tell you the result of your test as a set of numbers. Doctors often use a certain number as a cutoff for a positive result. For example, your doctor may say the cutoff is 1 out of This means that if your result is 1 out of or 1 out of a number less than such as 1 out of , you have a positive result and your baby has a higher chance of a birth defect. If your result is 1 out of , this means that you have a negative result and your baby has a lower chance of a birth defect.

Ultrasound test for fetal nuchal translucency NT. This test uses ultrasound to look at the back of the baby's neck. It checks for increased fluid or skin thickening. These might mean a defect. Blood tests. The blood tests measure 2 substances found in the blood of all pregnant women:. This protein is made by the placenta in early pregnancy. Abnormal levels could mean an increased risk for a chromosome defect.

Human chorionic gonadotropin hCG. This hormone is made by the placenta in early pregnancy. Cell-free fetal DNA screening.

This tests the baby's DNA that is in your blood. It checks for certain abnormal chromosomes. Low levels may be related to certain birth defects. How are the tests done? A simple blood test is all that's needed for the rest of the first-trimester screening. The health professional taking a sample of your blood will: Wrap an elastic band around your upper arm. This makes the veins below the band larger so it is easier to put a needle into the vein. Clean the needle site with alcohol.

Put the needle into the vein. Attach a tube to the needle to fill it with blood. Remove the band from your arm when enough blood is collected.

Put a gauze pad or cotton ball over the needle site as the needle is removed. Put pressure on the site and then put on a bandage.

How accurate are the tests? The nuchal translucency test correctly finds Down syndrome in 64 to 70 out of fetuses who have it. It misses Down syndrome in 30 to 36 out of fetuses. This also means that these tests miss it in 13 to 18 out of fetuses. This also means that the test misses Down syndrome in 4 out of fetuses.

What do the results mean? What do you do with the results? If you have a negative result, you may choose not to have any more tests. Should you have first trimester screening? Screening for fetal aneuploidy.

Obstetrics and Gynecology , 5 : e—e Your health care provider will use your age and the results of the blood test and ultrasound exam to gauge your risk of carrying a baby with Down syndrome or trisomy Other factors — such as a prior Down syndrome pregnancy — also might affect your risk.

First trimester screening results are given as positive or negative and also as a probability, such as a 1 in risk of carrying a baby with Down syndrome.

First trimester screening correctly identifies about 85 percent of women who are carrying a baby with Down syndrome. About 5 percent of women have a false-positive result, meaning that the test result is positive but the baby doesn't actually have Down syndrome. When you consider your test results, remember that first trimester screening indicates only your overall risk of carrying a baby with Down syndrome or trisomy A low-risk result doesn't guarantee that your baby won't have one of these conditions.

Likewise, a high-risk result doesn't guarantee that your baby will be born with one of these conditions. If you have a positive test result, your health care provider and a genetics professional will discuss your options, including additional testing.

For example:. Your health care provider or a genetic counselor will help you understand your test results and what the results mean for your pregnancy. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview Nuchal translucency measurement Open pop-up dialog box Close.

Nuchal translucency measurement First trimester screening includes an ultrasound exam to measure the size of the clear space in the tissue at the back of a baby's neck nuchal translucency. More Information Prenatal testing: Quick guide to common tests.