Pregnancy Tests and Screenings by Trimester: What to Expect, When, and Why It Matters

A positive pregnancy test is just the beginning. Over the next nine months, you'll be offered a series of blood draws, ultrasounds, and screenings that can feel overwhelming, especially when no one has explained what each one is actually looking for.

This guide breaks down every major prenatal test and screening by trimester, in plain language, so you know what's coming, why it matters, and what your results actually mean. Knowledge doesn't replace the conversation with your provider, but it makes that conversation a lot easier to have.

Key takeaway: Prenatal testing falls into two categories: screening tests (which estimate risk) and diagnostic tests (which confirm or rule out a condition). Most routine tests are screenings. A concerning result doesn't mean something is wrong; it means more information is needed.

First Trimester Screenings (Weeks 1–13)

The first trimester is the most test-intensive period of pregnancy. Your provider is establishing a baseline for your health, confirming the pregnancy is developing normally, and beginning to assess risk for chromosomal conditions.

Your First Prenatal Visit: The Baseline Panel

At your first appointment (usually between weeks 8 and 10), expect a comprehensive blood and urine workup. This isn't optional or precautionary, it's foundational. These tests establish what's normal for you, so any changes later in pregnancy can be caught early.

The standard first-visit panel includes:

• Complete blood count (CBC): Checks for anemia, which affects roughly 15–20% of pregnant women in the US and can impact fetal development if left unaddressed
• Blood type and Rh factor: If you're Rh-negative and your baby is Rh-positive, your body can develop antibodies that affect future pregnancies; this is preventable with timely treatment
• Rubella immunity: Rubella infection in early pregnancy carries serious risks for the baby, including hearing loss and heart defects
• Infectious disease screening: HIV, hepatitis B, hepatitis C, syphilis, and other STIs are tested routinely because early detection allows for treatment that protects both mother and baby
• Thyroid function (TSH): Undiagnosed hypothyroidism increases miscarriage risk and can affect fetal brain development
• Urinalysis and urine culture: Screens for asymptomatic urinary tract infections, which are more common in pregnancy and can trigger preterm labor if untreated
• HCG levels: Confirms the pregnancy and helps establish gestational age. Learn more about what HCG levels mean week by week.

Your first visit is also when your provider will discuss prenatal vitamins, if you haven't started them already. The key nutrients are folate (400–800 mcg daily, ideally started before conception), iron, calcium, vitamin D, and omega-3 fatty acids. One tablet daily is the standard recommendation; taking more than directed offers no benefit and can cause side effects including nausea, constipation, and stomach cramps. If your prenatal vitamin upsets your stomach, take it with food or before bed - and ask your provider about alternatives before switching on your own.

Nuchal Translucency Ultrasound (Weeks 11–14)

This ultrasound measures the fluid at the back of the baby's neck (called nuchal translucency). A thicker measurement can indicate an increased risk for Down syndrome (trisomy 21) or other chromosomal conditions. It's typically combined with a blood test measuring PAPP-A (pregnancy-associated plasma protein A) and hCG in what's called first trimester combined screening.

This combined approach detects approximately 85% of Down syndrome cases, according to Mayo Clinic.

Results from the nuchal translucency ultrasound, PAPP-A, and hCG are combined with maternal age to calculate an overall risk factor - no single marker is assessed in isolation.

NIPT: The Most Sensitive Option (From Week 10)

Cell-free DNA screening, commonly called NIPT (non-invasive prenatal testing), analyzes fragments of fetal DNA circulating in the mother's bloodstream. It can be done as early as 10 weeks and is one of the most accurate screening tools available for chromosomal conditions including:

• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)
• Sex chromosome abnormalities

NIPT is a screening test, not a diagnostic one. A high-risk result should be followed up with diagnostic testing such as CVS or amniocentesis. NIPT can also tell you your baby's biological sex, if you want to know.

Chorionic Villus Sampling (CVS): Weeks 10–13

CVS is a diagnostic test, not a screening. It involves taking a small sample of placental tissue to analyze the baby's chromosomes directly. It's offered when screening results indicate elevated risk, or when there's a family history of a chromosomal or genetic condition. CVS carries a small procedural risk (approximately 0.5–1%) and is typically only offered when the benefit of a definitive answer outweighs that risk.

Mental Health Screening: Often Overlooked, Always Important

ACOG recommends that screening for perinatal depression and anxiety occur at the initial prenatal visit, later in pregnancy, and at postpartum visits. 

This matters because anxiety and depression during pregnancy are more common than gestational diabetes, affecting an estimated 1 in 5 pregnant women. Left unaddressed, prenatal mental health conditions can affect sleep, nutrition, and even birth outcomes. If your provider doesn't ask, bring it up yourself.

Second Trimester Screenings (Weeks 14–26)

The second trimester brings a different kind of testing: less focused on confirming the pregnancy and more focused on understanding how your baby is growing and whether any structural differences are present.

The Anatomy Ultrasound (Weeks 18–22)

This is the most comprehensive ultrasound of pregnancy and one that most expectant parents look forward to. Done between 18 and 22 weeks, the anatomy scan examines:

• Brain, spine, and skull
• Heart structure and function
• Kidneys, stomach, and abdominal wall
• Arms, legs, hands, and feet
• Placenta location and amniotic fluid levels
• Overall fetal growth measurements

This scan can detect many structural differences that blood tests cannot. If something warrants a closer look, your provider may refer you to a maternal-fetal medicine specialist for a targeted ultrasound. It's also when most parents choose to find out their baby's sex.

Types of Ultrasound Used During Pregnancy

Not all ultrasounds are the same. The type your provider orders depends on what they're looking for and how far along you are:

Ultrasound uses sound waves, not radiation, and has been used safely in obstetric care for over 30 years. It is not a perfect tool - it may not catch every birth defect, and occasionally a normal pregnancy will produce a finding that requires follow-up. Most follow-up scans confirm everything is fine.

The Quad Screen (Weeks 15–22)

The quad screen (also called the multiple marker test or AFP test) measures four substances in your blood:

The quad screen is a risk assessment tool, not a diagnosis. Results are expressed as a probability (e.g., 1 in 1,200 risk for Down syndrome), and most women with an elevated risk will have a healthy baby. If you already had NIPT in the first trimester, your provider may not recommend the quad screen.

Gestational Diabetes Screening (Weeks 24–28)

Gestational diabetes affects approximately 6-9% of pregnancies in the United States, according to the Eunice Kennedy Shriver National Institute of Child Health and Human Development, making this one of the most clinically significant screenings of the second trimester.

The standard approach is a two-step process:

1. Glucose challenge test (GCT): You drink a glucose solution and have blood drawn one hour later. No fasting required. If your blood sugar is above the threshold, you move to step two.
2. Glucose tolerance test (GTT): A three-hour test done after fasting overnight. Blood is drawn at multiple intervals. Two or more abnormal values confirm gestational diabetes.

Gestational diabetes that's identified and managed appropriately does not mean a high-risk pregnancy. It means close monitoring and, in many cases, simple dietary adjustments.

Amniocentesis (Weeks 15–20)

Like CVS in the first trimester, amniocentesis is a diagnostic test, not a routine screening. A small amount of amniotic fluid is withdrawn and analyzed for chromosomal or genetic conditions. It's typically offered when:

• First or second trimester screening results show elevated risk
• There is a known family history of a genetic condition
• The anatomy scan reveals a structural difference that warrants further investigation

The procedure carries a small risk of miscarriage (approximately 0.1–0.3%), which is why it's reserved for situations where the information gained outweighs the risk.

Ongoing Monitoring at Every Visit

At every second-trimester appointment, your provider will check several things that don't make headlines but matter consistently:

• Blood pressure and urine protein: The primary early detection method for preeclampsia, which affects 5–8% of pregnancies and can develop rapidly
• Fundal height: A tape measure from your pubic bone to the top of the uterus (fundus). In centimeters, it should roughly equal your gestational week after week 20. Measurements that are significantly off can prompt further investigation into fetal growth.
• Fetal heart tones: Your provider will listen to the baby's heartbeat at each visit using a handheld Doppler device, typically from around week 10–12 onward

These routine checks are quick but cumulative - they build a picture of your pregnancy's trajectory that a single test never could.

Third Trimester Screenings (Weeks 27–40)

By the third trimester, the focus shifts from development to readiness: is your baby growing well, is your body coping, and is everything in position for a safe delivery?

Group B Streptococcus (GBS) Screening (Weeks 35–37)

Group B Strep is a common bacterium that lives harmlessly in many adults but can cause serious illness in newborns if passed during delivery. The test is simple: a swab of the vagina and rectum. If you test positive (roughly 25% of pregnant women do), you'll receive IV antibiotics during labor, which dramatically reduces the risk of transmission to the baby.

Testing positive for GBS is not an infection, not a sexually transmitted disease, and not a sign anything is wrong. It simply means your care team will take a specific precaution during birth.

Repeat Blood Tests

Several of the blood tests from your first trimester are repeated in the third trimester to catch any changes:

• Complete blood count: Anemia is more common as pregnancy progresses and blood volume increases
• Blood glucose (fasting): If your earlier gestational diabetes screen was borderline, this may be rechecked
• HIV and syphilis: Repeated in the third trimester per CDC guidelines, as late-stage transmission to the baby is preventable with treatment

Third Trimester Ultrasound

Not every pregnancy requires a third-trimester ultrasound, but your provider may order one to check:

• Fetal growth: Ensuring the baby is growing on track and not measuring significantly large or small for gestational age
• Amniotic fluid levels: Low fluid (oligohydramnios) or excess fluid (polyhydramnios) can signal complications
• Placenta position: If the placenta was low-lying earlier in pregnancy, a follow-up scan confirms whether it has moved away from the cervix
• Baby's position: Confirming head-down presentation as the due date approaches

Fetal Movement Monitoring (Kick Counts)

From around week 28, your provider may ask you to track fetal movement, often called "kick counts." While not a clinical test in the traditional sense, monitoring your baby's movement pattern is one of the simplest ways to detect potential problems between appointments. A change in your baby's typical movement pattern is worth calling your provider about promptly.

Biophysical Profile and Non-Stress Test

For pregnancies that are post-term or have specific risk factors, providers may order:

• Non-stress test (NST): Monitors the baby's heart rate in response to its own movements using a fetal monitor. A "reactive" result (heart rate increases with movement) is reassuring.
• Biophysical profile (BPP): Combines the NST with an ultrasound that assesses breathing movements, body movements, muscle tone, and amniotic fluid levels. Scored out of 10.

These tests are typically reserved for specific clinical situations, not routine for all pregnancies.

Your Prenatal Testing Timeline at a Glance

Use this reference table to track what's typically offered and when. Your provider may adjust this based on your individual health history.

Every visit: Blood pressure and urine protein are checked at each prenatal appointment throughout all three trimesters.

When Results Feel Scary: What to Remember

An unexpected result on a prenatal screening is one of the most anxiety-inducing experiences of pregnancy. It's worth being clear about what screening results actually mean, because the language around them can be genuinely confusing.

Screening vs. Diagnosis: The Critical Distinction

A screening result that comes back "high risk" or "abnormal" does not mean your baby has a condition. It means the statistical probability of a condition is higher than average. The vast majority of women who receive a high-risk screening result go on to have healthy babies.

Diagnostic tests (CVS and amniocentesis) provide a definitive answer. Screening tests do not. Understanding this distinction can significantly reduce the emotional weight of waiting for results.

The Emotional Reality of Prenatal Testing

No amount of clinical information fully prepares you for the anxiety that can come with prenatal testing. Waiting for results, navigating what an "elevated risk" actually means, and making decisions about further testing can all feel overwhelming, even when everything turns out fine.

This is precisely why ACOG's recommendation for mental health screening at every prenatal visit matters so much. Anxiety during pregnancy is not just an emotional inconvenience; research shows it can affect sleep quality, cortisol levels, and even birth outcomes. You can read more about how stress during pregnancy affects your body and your baby on the Soula blog.

The practical takeaway: If you're feeling anxious between appointments, you don't have to wait until your next visit to address it. Soula's 24/7 AI support is built specifically for moments like these, offering a space to process worry, track your emotional state, and access calming tools whenever you need them.

Questions Worth Asking Your Provider

Walking into a prenatal appointment knowing what to ask makes a real difference. Here are questions that help you get more from each visit:

• "Is this test a screening or a diagnostic test, and what happens if the result is concerning?"
• "What are the benefits and risks of this test for my specific situation?"
• "Are there any tests I should have based on my family history or personal health history?"
• "What does a normal result look like, and how long until I hear back?"
• "How are you screening for anxiety and depression during this pregnancy?" (If they haven't asked, ask them.)

Your provider is your partner in this process. The more questions you bring, the more useful each appointment becomes.

Prenatal testing exists to give you and your care team the information needed to support the healthiest possible pregnancy. Most tests will come back reassuringly normal. The ones that don't are designed to open a conversation, not close one.

What's equally true is that the emotional experience of pregnancy deserves the same attention as the physical one. If you're looking for support that goes beyond the clinical, Soula's pregnancy-focused AI tools are available around the clock to help you track how you're feeling, manage anxiety, and feel less alone between appointments. Explore the Soula app to see how it supports women through every stage of pregnancy.

Frequently Asked Questions

What is the difference between a screening test and a diagnostic test?

A screening test estimates the probability that a condition is present. It cannot confirm or rule out a diagnosis. A diagnostic test, such as CVS or amniocentesis, analyzes genetic material directly and provides a definitive answer. Most routine prenatal tests are screenings. A high-risk screening result means more information is needed, not that something is wrong.

When is the first prenatal appointment, and what tests are done?

The first prenatal appointment typically happens between weeks 8 and 10. It includes a comprehensive blood panel covering blood type, Rh factor, CBC, thyroid function, rubella immunity, infectious disease screening (HIV, hepatitis B, hepatitis C, syphilis), and a urinalysis. hCG levels may also be checked to confirm the pregnancy and establish gestational age.

Is NIPT better than the nuchal translucency ultrasound?

They test for similar things but work differently. NIPT analyzes fetal DNA in the mother's blood and is more sensitive, detecting approximately 99% of Down syndrome cases. The nuchal translucency ultrasound measures fluid at the back of the baby's neck and is combined with blood markers (PAPP-A and hCG) for a composite risk score. Many providers offer both; some offer NIPT as a standalone option. Neither is diagnostic on its own.

What happens if my gestational diabetes screening comes back abnormal?

A positive result on the one-hour glucose challenge test (GCT) does not confirm gestational diabetes. It means you move on to the three-hour glucose tolerance test (GTT), which is more definitive. Two or more abnormal values on the GTT confirm the diagnosis. Gestational diabetes that is identified and managed appropriately does not automatically make your pregnancy high-risk.

Is the GBS test the same as an STI test?

No. Group B Streptococcus (GBS) is a common bacterium found in the digestive and reproductive tracts of roughly 25% of healthy adults. It is not a sexually transmitted infection. Testing positive simply means your care team will administer IV antibiotics during labor to prevent transmission to the baby, which is highly effective.

Do I have to have every test that's offered?

Prenatal testing is offered, not mandated. You can decline any test after discussing the implications with your provider. Some tests, like blood pressure monitoring at each visit, are considered standard of care. Others, like NIPT or amniocentesis, involve a decision that depends on your personal values, risk tolerance, and family history. Your provider can help you weigh the benefits and risks of each.

How common is anxiety during pregnancy, and should I mention it to my provider?

Anxiety and depression during pregnancy affect an estimated 1 in 5 pregnant women, making them more common than gestational diabetes. ACOG recommends screening for both at the first prenatal visit, during pregnancy, and at postpartum visits. If your provider hasn't asked, bring it up. Prenatal mental health is a clinical concern, not just an emotional one, and early support makes a real difference.