Twin Pregnancy: Prenatal Tests in the First Trimester

Finding out you are pregnant with twins can be both exciting and overwhelming. You want to be sure your babies are growing and developing normally and that you are doing all the right things for a healthy pregnancy.

Even if you are healthy, twins turn this into a high-risk pregnancy for you. For this reason, your doctor will want to watch you and your babies closely. You'll have all the routine tests, but expect to have some of them earlier and more often.

Soon after you find out you're pregnant with twins, your doctor may suggest consulting a perinatologist, also called a maternal fetal medicine specialist. These doctors are obstetricians who specialize in high-risk pregnancies. He or she may work with your regular obstetrician to manage your pregnancy and order tests.

Routine Tests

When you find out you're pregnant, your doctor will want to quickly get an idea of your overall health.

History and physical exam. During your first or second prenatal visit, you'll answer a lot of questions about your health and family histories. This information helps the doctor know whether you have any specific risks to address, such as an inherited genetic disorder. You will also have a physical exam. Your doctor will calculate your due date based on the date of your last menstrual period. An ultrasound will help confirm that this due date is correct.

Pelvic exam and Pap smear. Prenatal testing during the first trimester begins with a pelvic exam and Pap smear to assess the health of your cervical cells. This test screens for cervical cancer and for certain sexually transmitted diseases.

Blood tests. During this initial visit, you will also have a panel of blood tests. These tests help identify:

  • Infections such as hepatitis or syphilis. (An HIV test is optional.)
  • Risks for German measles and chickenpox, both of which can be very serious during pregnancy
  • Signs of illness, such as anemia, which is more common with twins
  • Your blood type and Rh factor to see if your blood and the babies' blood are compatible

Urine tests. Along with blood pressure checks, urine tests at every prenatal visit give a quick and easy snapshot of your health. They can reveal:

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Optional Screening for Birth Defects

Late in your first trimester, your doctor may offer you screening for birth defects. Know that your doctor may instead offer you this screening in the second trimester. Or he or she may offer it in both trimesters.

This optional screening involves a blood test and a nuchal translucency ultrasound or "first trimester screen." If results from these tests show an increased risk for birth defects, you may need other tests as well.

Blood test. The blood test measures two proteins in your blood, which can be signs of certain genetic defects such as Down syndrome.

Nuchal translucency ultrasound. This involves measurement of the back of each baby's neck (called the nuchal fold). If this fold of skin is thicker than normal, it may be a sign of a birth defect. You may have a more detailed ultrasound if results from the nuchal ultrasound indicate a possible problem.

Chorionic villus sampling (CVS). If you are over 35 or if screening shows an increased risk for chromosomal abnormalities, your doctor may recommend this test. It requires removing a sample of cells from the placenta. You can have this test between weeks 10 and 12. (Doctors can perform a similar test, amniocentesis, in the second trimester. You and your doctor can decide which option is better for you.)

Carrier screening for cystic fibrosis. You may also have an optional test for this inherited disease. It is a blood or saliva test.

Now what? If you find you are at risk for having a baby with a birth defect or genetic abnormality, or if test results indicate one is present, you may want to consult a genetic counselor. This person can help you understand the test results and risks, and can help you understand your options.

WebMD Medical Reference Reviewed by Trina Pagano, MD on January 20, 2019

Sources

SOURCES:

Lucile Packard Children's Hospital at Stanford. "Common Tests During Pregnancy."

U.S. Department of Health and Human Services Office on Women's Health. "Prenatal care and tests." 

March of Dimes: "Routine prenatal tests" and "Multiples: twins, triplets and beyond."

American College of Nurse Midwives. "First Trimester Tests."

The American College of Obstetricians and Gynecologists. "Screening for Birth Defects,"  "FAQ on Having Twins," and YourPregnancy and Childbirth, Month to Month. 5th edition. 2010.

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