Ultrasound and other prenatal tests what to expect
Pregnancy & Parenting
11 Min Read

Ultrasound and Other Prenatal Tests: What to Expect

Prenatal tests are key to monitoring your baby's health and development during pregnancy. Here's a quick overview of what you'll encounter:

  • First Trimester (Weeks 1–13):

    • Ultrasound: Confirms pregnancy, checks heartbeat, and calculates due date.
    • NIPT Blood Test: Screens for chromosomal conditions like Down syndrome.
    • Combined Screening: Blood tests and ultrasound to check for genetic risks.

  • Second Trimester (Weeks 14–26):

    • 20-Week Ultrasound: Detailed anatomy scan of organs, bones, and placenta.
    • Quad Screen: Blood test for neural tube defects and chromosomal conditions.
    • Amniocentesis (Optional): Diagnoses genetic conditions with 99.4% accuracy.

  • Third Trimester (Weeks 27–40):

    • Growth Ultrasounds: Tracks baby's size and amniotic fluid levels.
    • Strep B Test: Screens for bacteria that could affect delivery.
    • Baby Monitoring: Nonstress Test (NST) or Biophysical Profile (BPP) for heart rate and movement.

Key Takeaways:

  • Screening Tests: Assess risk but don’t confirm conditions.
  • Diagnostic Tests: Provide definitive answers but are more invasive.
  • Your Choice Matters: Tests are optional and should align with your needs.

Talk with your healthcare provider to understand each test and make informed decisions.

Prenatal Care: 1st, 2nd, and 3rd Trimester Visits

Tests During Weeks 1-13

During the first trimester, several tests help set the stage for your prenatal care. These screenings provide essential information about your pregnancy and check for any potential issues. Here's a closer look at the key tests during this period.

First Ultrasound

Your first ultrasound typically happens between weeks 7–8 or around week 12, depending on your healthcare provider. This scan confirms your pregnancy, calculates gestational age, and offers insights into your baby's early development.

The main thing is to confirm pregnancy dating to make sure we have an accurate due date, to make sure that we're able to see the baby's heartbeat, and to see if there's one, or more than one, fetus. – Rebecca Jackson, MD, assistant professor of obstetrics and gynecology [3]

During the procedure, your provider confirms the baby's heartbeat (detectable as early as 6 weeks), measures the fetus to determine gestational age, checks for multiples, and examines reproductive structures. They also look for complications like ectopic pregnancy.

For the best images before 12 weeks, a transvaginal ultrasound may be used. After 12 weeks, an abdominal ultrasound is typically performed.

NIPT Blood Test

The Non-Invasive Prenatal Testing (NIPT) blood test becomes an option at week 10. This test analyzes cell-free DNA in your blood to evaluate the risk of common chromosomal conditions.

Here are the detection and false positive rates for some conditions:

Condition Detection Rate False Positive Rate
Down syndrome 99% ~1 in 1,054
Edwards' syndrome 84% ~1 in 930
Patau's syndrome 87% ~1 in 4,265

Combined First Trimester Screen

Between weeks 11 and 13+6, this screening combines blood tests (measuring PAPP-A and total ß-hCG), an ultrasound to assess nuchal translucency, nasal bone development, and crown-rump length.

This test identifies about 85% of Down syndrome cases and 90% of trisomy 18 cases in single pregnancies [4]. Approximately 5% of women receive a screen-positive result, which may lead to further testing [4].

Tests During Weeks 14-26

In the second trimester, several tests help monitor your baby's development and your health. Here's a breakdown of the key screenings during this period.

20-Week Detailed Ultrasound

The anatomy scan, usually done between weeks 18 and 22, is a detailed ultrasound that takes about 30 minutes. It provides a close look at your baby's physical development.

The 20-week scan is done to check if your baby could have a condition that affects their health and development. - NHS [5]

During this scan, your provider will check:

  • Your baby’s organs, including the heart, brain, and kidneys
  • Bone structure and spinal cord
  • Facial features
  • The position of the placenta
  • Blood flow in the uterus

Preparation tips:

  • Wear loose, comfortable clothing
  • Remove any belly piercings
  • Bring your maternity notes
  • Follow instructions about how full your bladder should be

4-Part Blood Screen

The quad screen, done between weeks 15 and 22, measures four substances in your blood to evaluate risks for certain conditions:

Substance Purpose
Alpha-fetoprotein (AFP) Checks for neural tube defects
Human chorionic gonadotropin (hCG) Screens for chromosomal conditions
Unconjugated estriol (uE3) Assesses developmental concerns
Inhibin A Adds additional markers for risk

This test is most accurate when performed between weeks 16 and 18 [7]. Your healthcare provider will also factor in your age, weight, ethnicity, and gestational age when interpreting the results.

Amniotic Fluid Test

Amniocentesis, offered between weeks 15 and 20, provides precise genetic information about your baby. It’s often recommended for women over 35 or those with unusual screening results.

Amniocentesis is still the gold standard for the diagnosis of chromosomal and genetic disorders. - Cleveland Clinic [10]

Key details:

  • Accuracy rate of 99.4% [9]
  • Less than 1% risk of miscarriage [8]
  • Detects conditions like Down syndrome, cystic fibrosis, and neural tube defects
  • Requires 24 hours of rest after the procedure

This test is optional but can confirm earlier screening results and provide clarity.

Diabetes Screening

Between weeks 24 and 28, a glucose test checks for gestational diabetes. You’ll drink a sugary solution, and your blood sugar will be tested an hour later. If the results are high, your provider may recommend a glucose tolerance test.

Your doctor will discuss the results and any necessary next steps. Don’t hesitate to ask questions if you need more information.

Tests During Weeks 27-40

In the final trimester, healthcare professionals perform several tests to check your baby's health and ensure a safe delivery.

Growth Check Ultrasounds

Growth check ultrasounds track your baby's progress during the third trimester. These scans measure key factors like head and abdomen size, femur length, amniotic fluid levels, placenta position, and blood flow. They are especially recommended if certain risk factors are present, such as:

  • Premature delivery
  • Gestational diabetes
  • BMI over 35
  • Previous small birthweight
  • Smoking

Strep B Test

Around weeks 35 to 37, you'll have a Group B Streptococcus (GBS) screening. This simple swab test checks for bacteria that could pose risks during delivery.

Screening women during pregnancy is one of the best ways to prevent GBS disease in the newborn's first week of life. – CDC [13]

Here are some key points about GBS:

Key Information Details
Occurrence Rate 1 in 4 pregnant women carry GBS [11][12]
Treatment Timing IV antibiotics needed at least 4 hours before delivery [11]
Risk Without Treatment 1–2% of babies develop GBS disease if the mother is positive [12]

In addition to infection screening, doctors may perform other tests to monitor your baby's overall health.

Baby Health Monitoring

Baby health monitoring includes tests like the Nonstress Test (NST) and the Biophysical Profile (BPP).

  • Nonstress Test (NST): Tracks your baby's heart rate in response to movement. A healthy response is an increase of at least 15 beats per minute for 15 seconds within a 20-minute period [15].
  • Biophysical Profile (BPP): Combines an NST with an ultrasound to evaluate movement, muscle tone, breathing, and amniotic fluid levels.

Monitoring can be done externally using abdominal devices or, during labor, internally by attaching a small electrode to the baby's scalp [14].

Reading Your Test Results

Understanding your prenatal test results helps you make informed decisions. Below, you'll find guidance on interpreting the results and determining your next steps. This section builds on your earlier testing experiences by explaining what the outcomes mean and outlining possible follow-up actions.

Types of Test Results

Prenatal tests fall into two categories: screening tests, which assess risk, and diagnostic tests, which provide definitive answers. Screening tests like NIPT (Non-Invasive Prenatal Testing) often use terms such as “Low Risk” or “High Risk.”

Result Type What It Means Follow-up Needed
Low Risk Less than 1 in 350 chance for trisomy 21 Typically, no further testing required
High Risk Greater than 1 in 350 chance for trisomy 21 Diagnostic testing is recommended
Screen Negative Low risk for chromosomal conditions Continue with routine prenatal care
Screen Positive Higher-than-threshold risk Confirmatory diagnostic testing needed

It's important to note that no prenatal screening test is completely accurate. For example, NIPT is a screening tool, not a diagnostic test [16].

Follow-up Testing

If your results indicate higher risk, further testing can confirm or rule out conditions. For instance, if NIPT results suggest high risk, diagnostic procedures like chorionic villus sampling (CVS) - usually done between 10–13 weeks - or amniocentesis, typically offered between 15–20 weeks, may be recommended [1]. Additional testing might also be suggested in cases of abnormal screenings, unusual ultrasound findings, or a family history of genetic conditions.

Doctor Discussions

Talking with your doctor about your results is a key part of deciding what to do next. Here are some areas to focus on during your discussions:

  • Understanding the Results: Ask for detailed explanations, including specific numbers and normal ranges, instead of relying on “positive” or “negative” labels [17].
  • Next Steps: Go over the recommended actions, including timelines, diagnostic options, potential risks, benefits, and insurance coverage.
  • Future Considerations: Discuss how the results might affect your prenatal care, delivery plans, or whether genetic counseling could be helpful.

If your cell-free DNA test comes back positive, it's critical to confirm the results with diagnostic testing, such as CVS or amniocentesis [6].

Help for Parents-to-Be

Prenatal testing can feel like a lot to handle. Services like cord blood banking add another layer of protection for your family’s health. These services work alongside prenatal care, preparing you for potential future medical needs.

Cord blood banking is worth considering as part of your birth plan. Cord blood contains hematopoietic stem cells, which can treat over 80 FDA-approved conditions, including blood disorders, immune deficiencies, and some cancers [18]. Just like prenatal tests guide your care, cord blood banking helps protect your child’s future.

Americord provides several stem cell banking services:

  • Cord Blood Banking: Uses CryoMaxx™ processing to maximize stem cell yield, stored in 5-compartment bags for flexible treatment options [21].
  • Cord Tissue Banking: Preserves mesenchymal stem cells (MSCs), which are being studied for conditions like Alzheimer’s and diabetes [21].
  • Placental Tissue Banking: Preserves additional MSCs that match the mother’s genetics [22].

Cord blood contains cells called hematopoietic stem cells. These cells can turn into any kind of blood cell and can be used for transplants that can cure diseases such as blood disorders, immune deficiencies, metabolic diseases, and some kinds of cancers.

To give yourself enough time, talk with your healthcare provider about cord blood banking before you reach 34 weeks of pregnancy [18].

For families exploring private banking, Americord offers clear pricing with no hidden fees. Their Cord Blood Quality Guarantee covers up to $110,000 for another source of stem cells if engraftment fails. This commitment has made Americord the top parent-preferred choice for stem cell banking [20].

Summary

Prenatal tests play a key role in monitoring both maternal and fetal health during pregnancy. Knowing what these tests involve can help you make informed choices about your care.

Key Testing Milestones

  • First trimester: Blood tests and ultrasounds are used to evaluate chromosomal risks.
  • Second trimester: Includes detailed anatomy scans and blood screenings to check for birth defects.
  • Third trimester: Focuses on monitoring growth and screening for Group B streptococcus, which affects about 25% of women. Antibiotics can reduce the risk of neonatal infection by 20 times [1][24].

These milestones provide a framework for ongoing conversations with your healthcare provider. Combined first- and second-trimester screenings can identify up to 95% of Down syndrome cases [24]. Your provider will tailor recommendations based on your individual needs.

One of the important distinctions to make is whether the test is for screening or diagnosis. A diagnostic test is more invasive and can convey a clear 'yes' or 'no' about a condition or disease a baby has.
– Katherine Harper Campbell, MD, MPH, Medical Director of Yale Medicine's Maternal-Fetal Medicine section [23]

Maintaining open communication with your provider is essential for understanding test results and making informed decisions. Remember, prenatal testing is optional, and your choices should reflect your values and circumstances. If you have a family history of specific conditions, consulting a genetic counselor may provide additional insights [2].

Tips for Optimal Care

  • Discuss the purpose of each test with your provider.
  • Share any concerns as soon as they arise.
  • Keep detailed records of your tests and results.
  • Ask questions to ensure your care aligns with your needs.