First trimester: Screens and tests

First trimester: Screens and tests

Regular prenatal visits will help ensure the best possible health for your baby. At each visit your weight, blood pressure, and the size of your uterus will be monitored. These measurements can reassure you that your pregnancy is going well.

Regular visits can also alert your health care provider to early signs of a problem. Early detection usually means problems can be treated more easily. At some visits you will be offered screening for specific concerns.

Your health care provider will determine if your urine will be checked for protein and sugar based on conditions in your pregnancy.

Prenatal screening

Knowing about some problems before your baby is born can help you and your health care provider be better prepared.

No test can guarantee that you will have a healthy baby. There are no tests that can identify all types of birth defects and developmental problems. However, prenatal screens may help predict if you have an increased risk of carrying a baby with some specific conditions

Prenatal screening tests are optional for all pregnant people to assess their risk of having a baby with a specific birth defect or genetic disorder. Genetic counseling can help you understand your testing.

When a screening result is "positive," it means that you are in a higher-risk category for a certain condition. It does not mean your baby has the condition. If you are at an increased risk, genetic counseling can help you understand the risks and clarify any concerns. You have the option for diagnostic testing which will determine if your baby actually has the condition.

If you have a high-risk pregnancy, you may need to have a one-hour glucose screen during the first trimester to test for gestational diabetes. You can read more about this screen in the Second trimester: Screens and tests section.

A "normal" or "negative" screen result indicates you are in a low-risk category. It does not definitely rule out the concern.

Talk with your health care provider about the benefits and limits of the offered screens. It is your choice whether or not to have a screening test.

Questions to ask your health care provider about a screen

  • What do you hope to learn from this screen? How would you use this information?
  • Are there risks to the screen?
  • If the screen is positive, how likely is it my baby has a condition?
  • If the screen is positive, what happens next?
  • If the screen is normal, how likely is it that my baby could have the condition?
  • What alternatives are there to having this screen?
  • How much does the screen cost?
Screen or test Why it may be offered

Chorionic villus sampling (CVS). A small amount of tissue is removed from your baby's developing placenta. These cells usually have the same genetic and biochemical makeup as your baby.

The cells are grown in a culture, and the chromosomes are studied. If the family history indicates additional concerns, other DNA or biochemical tests may also be done.

The sampling procedure is done using ultrasound to guide a catheter through your vagina and cervix. The sample can also be taken using ultrasound to guide a needle through your abdomen.

It is usually used to determine if your baby has specific genetic problems. The concern may be related to your age, family history, the results of a screen, or other factors.

The test is usually done at 10 to 12 weeks. ACOG supports this option for all pregnant people.

Cultures. Secretions and cells from the vagina, cervix or both are collected and analyzed.
Helps identify sexually transmitted diseases so they can be treated and your baby will not be at risk.

Cystic fibrosis carrier test. This is a blood test that can identify most carriers of an altered gene for cystic fibrosis (CF).

If you test positive, your partner will also be offered testing. Babies must have two altered CF genes in order to have cystic fibrosis. They are tested for CF after birth.

To determine if your baby is at risk for cystic fibrosis. If both parents are carriers, the baby has a one in four chance of having cystic fibrosis.

Because most parents do not learn they are carriers until they have an affected child, the test is offered to all couples.

Other carrier tests. Every pregnant person or couple has the option to be tested for inherited disorders. No carrier screen finds all carriers.
Certain conditions are more common in specific ethnic groups (such as sickle cell in African-Americans).

First trimester combined screen. An ultrasound is used to measure the fluid area behind the baby's neck (nuchal translucency). This information is combined with a blood test to measure two proteins made by the baby and placenta (PAPP-A and HCG).

For an even better detection rate, this screen can be done as part of a step-by-step process that includes a second blood test done in the second trimester. The combination of the first trimester test and second trimester test is called sequential or integrated screening.

This screen can help assess the risk of Down syndrome and trisomy 18, a more serious

condition. Those who are high risk are offered CVS or amniocentesis to determine if there is a chromosomal condition or rule it out. ACOG supports this option for all pregnant people.

An increased nuchal translucency measurement may also suggest a higher risk for birth defects, specifically heart defects and genetic conditions. Your baby's heart can be checked using a detailed ultrasound later in pregnancy.

HIV test. This blood test detects whether or not you have been exposed to HIV, the virus that causes AIDS.
HIV testing is recommended for all pregnant people. Early detection and treatment can reduce a baby's chances of getting HIV to 5 percent or less. You cannot be denied insurance on the basis of a positive HIV test.
Pap test. A swab collects cervical cells that are then viewed under a microscope.
This test is to detect changes in cervical cells that indicate infection or abnormal cells. Pap tests are recommended starting at age 21.
Prenatal profile. Blood is drawn and analyzed. This profile is part of standard care to determine blood type and RH factor. It also determines whether you are anemic, have immunity to German measles ( rubella), and have been infected with hepatitis B or syphilis.
Ultrasound. A transducer that sends sound waves is placed on your abdomen or in your vagina. It creates a picture of your baby on a monitor screen. To determine your baby's age, your due date, and to detect more than one baby. It can also be used to detect a variety of physical birth defects, measure your baby's growth, and assess well-being. You may or may not be able to tell your baby's gender from an ultrasound.

Noninvasive prenatal testing (NIPT) is a screening test that measures the amount of DNA from the placenta of a pregnant person's blood. The test has a high detection rate for the most common chromosome abnormalities including Down syndrome, trisomy 18, trisomy 13 and sometimes sex chromosome abnormalities.

A maternal blood sample can be analyzed after 10 weeks of pregnancy. While the detection rate is high, false-positive and false-negative results can occur. For this reason, testing such as amniocentesis is recommended for confirmation of a high-risk result.

You and your health care provider will decide if this test is right for you. Currently, ACOG supports noninvasive prenatal testing if you are considered high risk for a chromosome abnormality.

Risk factors include: age 35 or older at delivery or having had a previous pregnancy with a chromosome abnormality, an abnormal serum screening test or an abnormal ultrasound.

Testing options by trimester

There are some additional first-trimester tests to identify potential problems related to you or your baby's health. Your health care provider will review the tests that are available to you. Use this  worksheet to record the results of your screenings and tests.

Questions to ask your health care provider about a test

  • What do you hope to learn from this test?
  • How accurate is it?
  • How many times have you (or the health care provider or technician) done this procedure before?
  • What risks does this test pose to my baby and me?
  • Who “reads” the test results? How reliable are the results?
  • How long will it take to get the test results back?
  • When the results come back, what options will I have?
  • What are the alternatives to having this test?
  • Where can I learn more about this test?
  • How will my test results change the care of my pregnancy?
  • If I have more questions, how can I schedule an appointment with a genetic counselor?

Source: Allina Health Patient Education, Beginnings: Pregnancy, Birth and Beyond, eighth edition, ob-ah-90026
First Published: 10/04/2002
Last Reviewed: 12/06/2021