Important Tests in Third Trimester of Pregnancy: Week by Week

Tests in the third trimester of pregnancy help doctors monitor your baby’s growth, maternal health, and readiness for delivery.

The third trimester marks the final stretch of pregnancy.

Between 28 and 40 weeks, your body prepares for labour, your baby continues to grow rapidly, and antenatal appointments become more frequent.

Along with these visits, your healthcare provider may recommend several tests designed to monitor both maternal and fetal health.

Many parents find this stage exciting, but it can also feel overwhelming.

Questions such as “Why do I need another blood test?”, “What is a non-stress test?”, or “Will these tests affect my birth plan?” are very common.

Understanding the purpose of third-trimester pregnancy tests can reduce anxiety and help you feel more informed throughout late pregnancy.

As a women’s health physiotherapist,

I often reassure expectant mothers that most third-trimester tests are routine and are performed to ensure that both mother and baby remain healthy as the due date approaches.

Why Are Pregnancy Tests Important During the Third Trimester?

Pregnancy can change significantly during the final weeks.

Conditions such as gestational hypertension, preeclampsia, fetal growth restriction, or gestational diabetes may develop or progress during late pregnancy.

Regular testing allows healthcare providers to:

• Monitor fetal growth and well-being.
• Detect complications early.
• Assess placental function.
• Identify infections that could affect the baby.
• Guide decisions regarding labour and delivery.

The primary goal of third-trimester surveillance is to reduce maternal and fetal complications while optimizing pregnancy outcomes. (Umana et al. 2024)

Blood Pressure Monitoring

One of the simplest yet most important tests performed during every antenatal visit is blood pressure assessment.

Healthcare providers closely monitor blood pressure because elevated readings may indicate:

• Gestational hypertension.
• Preeclampsia.
• Chronic hypertension.

Preeclampsia is a potentially serious pregnancy complication characterised by high blood pressure and signs of organ involvement.

Early detection allows timely intervention and may significantly improve outcomes.

Many women with high blood pressure experience no obvious symptoms, which is why routine monitoring remains essential.

Urine Testing

Urine testing is routinely performed during many antenatal appointments.

A urine sample may be assessed for:

• Protein.
• Glucose.
• Signs of urinary tract infection.
• Ketones.

The presence of protein in the urine, particularly when accompanied by elevated blood pressure, may suggest preeclampsia.

Urinary tract infections identified during pregnancy require treatment because untreated infections may increase the risk of complications.

Blood Tests During the Third Trimester

Some women undergo repeat blood investigations during late pregnancy.

Common blood tests include:

Complete Blood Count (CBC)

A CBC evaluates:

• Haemoglobin levels.
• Red blood cells.
• White blood cells.
• Platelets.

Anaemia can develop during pregnancy and may contribute to fatigue, weakness, and complications around delivery.

Blood Group and Antibody Screening

Additional antibody testing may be required in selected pregnancies, particularly among women who are Rh-negative.

Repeat Infection Screening

Depending on local guidelines and individual risk factors, healthcare providers may recommend repeat screening for certain infections.

Growth Ultrasound Scans

Growth scans are among the most common third-trimester investigations.

These ultrasounds evaluate:

• Fetal growth.
• Estimated fetal weight.
• Baby’s position.
• Placental location.
• Amniotic fluid levels.

Growth scans are frequently recommended when:

• The baby appears small or large.
• Maternal medical conditions are present.
• There is a history of pregnancy complications.
• Fundal height measurements are abnormal.

Serial scans often provide more useful information than a single ultrasound because they help assess growth trends over time.

Group B Streptococcus (GBS) Screening

One of the most important third-trimester tests performed between approximately 35 and 37 weeks of pregnancy is Group B Streptococcus (GBS) screening.

GBS is a type of bacteria commonly found in the gastrointestinal and genital tracts.

Most women carrying GBS have no symptoms.

However, the bacteria can occasionally be transmitted to the baby during labour and may cause serious neonatal infection.

Screening usually involves a simple swab from the vagina and rectum.

Women who test positive may receive antibiotics during labour to reduce the risk of newborn infection. (Verani et al. 2010)

Non-Stress Test (NST)

A non-stress test evaluates how the baby’s heart rate responds to movement.

During the test:

• Sensors are placed on the mother’s abdomen.
• Fetal heart rate is monitored.
• The baby’s movements are recorded.

A healthy fetus typically demonstrates temporary increases in heart rate during movement.

NSTs are frequently recommended in pregnancies complicated by:

• Diabetes.
• Hypertension.
• Reduced fetal movements.
• Post-term pregnancy.
• Fetal growth restriction.

The procedure is painless and usually takes approximately 20 to 40 minutes.

Biophysical Profile (BPP)

A biophysical profile combines ultrasound assessment with fetal heart rate monitoring.

The test evaluates:

• Fetal breathing movements.
• Fetal body movements.
• Fetal muscle tone.
• Amniotic fluid volume.
• Non-stress test findings.

Each component contributes to an overall score.

Biophysical profiles are commonly used in high-risk pregnancies or when additional fetal surveillance is required.

The goal is to identify babies who may require closer monitoring or delivery.

Doppler Ultrasound Studies

Doppler ultrasound is a specialised assessment that evaluates blood flow.

Healthcare providers may assess:

• Umbilical artery blood flow.
• Middle cerebral artery blood flow.
• Uterine artery blood flow.

Doppler studies are particularly valuable in pregnancies complicated by fetal growth restriction or placental insufficiency.

Research has shown that Doppler surveillance improves monitoring in high-risk pregnancies. (Messawa et al. 2012)

Fetal Movement Monitoring

Many healthcare providers encourage women to become familiar with their baby’s usual movement patterns during the third trimester.

Reduced fetal movement may be an early sign that additional evaluation is required.

If movements decrease noticeably, healthcare providers may recommend:

• Non-stress testing.
• Ultrasound assessment.
• Biophysical profile.
• Additional fetal surveillance.

A sudden reduction in fetal movements should never be ignored. (David et al. 2022)

A Physiotherapist’s Perspective: Coping With Test Anxiety

Many expectant mothers tell me that waiting for test results is often more stressful than the tests themselves.

A few strategies may help:

• Attend appointments with a support person.
• Write down questions beforehand.
• Practise diaphragmatic breathing.
• Continue approved physical activity.
• Avoid excessive internet searching.

Remember that most third-trimester tests are precautionary and frequently provide reassurance rather than identify serious problems.

What Happens If a Test Result Is Abnormal?

Receiving an abnormal test result during pregnancy can be frightening.

However, it is important to remember that an abnormal result does not automatically mean that something is seriously wrong.

Many test results simply indicate that additional monitoring is needed.

Depending on the findings, your healthcare provider may recommend:

• Repeat testing.
• Additional ultrasound scans.
• More frequent antenatal appointments.
• Referral to a maternal-fetal medicine specialist.
• Further blood investigations.
• Increased fetal surveillance.

The goal is always to identify concerns early and provide the safest possible care for both mother and baby.

In many cases, closer monitoring leads to healthy pregnancy outcomes.

Tests for Women With High-Risk Pregnancies

Women with high-risk pregnancies often require more frequent investigations during the third trimester.

You may undergo additional testing if you have:

• Gestational diabetes.
• High blood pressure or preeclampsia.
• Twin or multiple pregnancy.
• Previous pregnancy complications.
• Autoimmune disease.
• Kidney disease.
• Fetal growth restriction.
• Reduced fetal movements.

Additional monitoring may include serial growth scans, repeated non-stress tests, Doppler studies, or biophysical profiles.

The exact schedule depends on your individual circumstances.

Can Third-Trimester Tests Influence Your Birth Plan?

Absolutely.

Information gathered during late pregnancy often helps healthcare providers make decisions regarding labour and delivery.

For example:

• A breech baby may prompt discussions about external cephalic version or caesarean birth.
• Severe fetal growth restriction may lead to earlier delivery.
• Significant blood pressure elevations may require induction of labour.
• Abnormal fetal surveillance findings may indicate the need for urgent delivery.

Birth plans should remain flexible because recommendations may change as pregnancy progresses.

Remember that the ultimate goal is a safe birth for both mother and baby.

What Happens During Weekly Antenatal Visits After 36 Weeks?

Many women notice that antenatal appointments become more frequent during the final weeks.

These visits often include:

• Blood pressure measurement.
• Weight assessment.
• Urine testing.
• Assessment of fetal movements.
• Fundal height measurement.
• Fetal heart rate assessment.
• Discussion of labour symptoms.
• Review of scan or blood test results.

Your healthcare provider may also discuss:

• Signs of labour.
• Birth preferences.
• Pain relief options.
• When to go to the hospital.

These appointments provide an excellent opportunity to ask questions and discuss any concerns.

Can You Prepare for Third-Trimester Tests?

Most routine pregnancy tests require very little preparation.

However, a few practical steps may help:

• Carry previous reports and scan records.
• Wear comfortable clothing.
• Stay hydrated unless instructed otherwise.
• Write down questions before appointments.
• Arrive early to reduce stress.

As a physiotherapist, I often encourage expectant mothers to practise slow breathing exercises before tests.

Deep diaphragmatic breathing can help reduce anxiety and encourage relaxation during procedures.

What Third-Trimester Pregnancy Tests Cannot Predict

Modern medicine offers remarkable insight into pregnancy.

Nevertheless, no test can predict everything.

Third-trimester tests cannot guarantee:

• A complication-free labour.
• The exact timing of labour.
• A completely problem-free newborn period.
• Future developmental outcomes.
• Exact birth weight.

Healthcare providers always interpret test results alongside your symptoms, medical history, and clinical examination.

Understanding these limitations can help reduce unnecessary anxiety.

The Emotional Side of Pregnancy Testing

Frequent testing can sometimes create emotional exhaustion.

Many women describe feeling anxious before appointments and relieved afterward.

Others experience ongoing worry throughout late pregnancy.

These feelings are completely understandable.

You may find it helpful to:

• Share concerns with loved ones.
• Join antenatal support groups.
• Continue approved physical activity.
• Practise relaxation techniques.
• Discuss anxiety openly with your healthcare team.

As healthcare professionals, we recognise that emotional well-being plays an important role in overall pregnancy health.

Questions You May Want to Ask Your Doctor

Consider asking:

• Which third-trimester tests will I need?
• Are these tests routine or because of a specific concern?
• What do my results mean?
• Will I need additional monitoring?
• Could test findings affect my birth plan?
• What symptoms should prompt urgent medical review?
• When should I contact the maternity unit?

Writing down your questions before appointments can help ensure that you leave feeling informed and reassured.

Conclusion

Third-trimester pregnancy tests play a crucial role in ensuring the health and safety of both mother and baby during the final weeks before birth.

Although the number of appointments and investigations may sometimes feel overwhelming,

these assessments help healthcare providers identify concerns early and guide appropriate care.

As a women’s health physiotherapist,

I encourage expectant mothers to attend all scheduled appointments, ask questions whenever they feel uncertain, and communicate openly with their maternity team.

Every pregnancy is unique, and ongoing monitoring helps provide the safest possible journey toward birth.

Frequently Asked Questions (FAQs)

1. What tests are commonly performed during the third trimester of pregnancy?

Common third-trimester tests include blood pressure monitoring, urine testing, blood tests, growth ultrasound scans, Group B Streptococcus (GBS) screening, non-stress tests, Doppler studies, and biophysical profiles.

2. Why do I need Group B Streptococcus (GBS) screening during pregnancy?

GBS screening helps identify women who carry Group B Streptococcus bacteria. If the test is positive, antibiotics may be given during labour to reduce the risk of infection in the newborn.

3. What is a non-stress test (NST) in pregnancy?

A non-stress test monitors your baby’s heart rate and movements. It helps healthcare providers assess fetal well-being, particularly in high-risk pregnancies or when there are concerns about reduced fetal movements.

4. Are third-trimester pregnancy tests painful?

Most routine pregnancy tests, including blood pressure checks, urine testing, ultrasound scans, and non-stress tests, are painless. Some blood tests or swab tests may cause brief mild discomfort.

5. Will abnormal test results always mean something is wrong with my baby?

No. Abnormal results often indicate the need for additional monitoring rather than a serious problem. Many women with abnormal screening results go on to have healthy pregnancies and healthy babies.

6. Can third-trimester test results affect my birth plan?

Yes. Some test results may influence decisions regarding labour induction, timing of delivery, mode of birth, or the need for additional monitoring during labour.

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Medical Disclaimer!

This article has been reviewed and written under the guidance of our Head Physiotherapist, Dr. Kruti Raj (PT, MUHS,CPT,CMPT). The information shared is intended for educational purposes only and should not be considered a substitute for personalized medical advice, diagnosis, or treatment.

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