Third Trimester of Pregnancy

Third trimester of pregnancy: week 28 through birth

The third trimester begins at week 28 and continues until the end of pregnancy, commonly around week 40, although the actual timing of birth varies.

During this stage, fetal weight increases substantially, while the brain, lungs and nervous system continue maturing. Fetal movement, presentation, maternal symptoms and preparation for birth become increasingly important.

Saudi prenatal care includes important visits at 28, 32 and 36 weeks, followed by hospital follow-up at 38 and 40 weeks.

A clear reduction in fetal movement should not be dismissed simply because the baby has less room. Movement may feel different, but a concerning change from the usual pattern requires contact with the maternity team.

Which weeks and months are in the third trimester?

The third trimester covers approximately weeks 28–40.

• Month 7: weeks 27–30. Week 27 remains in trimester 2, while weeks 28–30 are in trimester 3.
• Month 8: weeks 31–35.
• Month 9: weeks 36–40.

You can also explore month 7, month 8 and month 9.

How does the fetus develop in the third trimester?

Development continues throughout trimester 3. This stage is characterized by growth, weight gain and further maturation of important organs and body systems.

Weeks 28–31: entering trimester 3

Brain and nervous-system development continues, body fat gradually increases and movement can become stronger and easier to recognize.

Week 28 also brings important care milestones, including follow-up, Rh-negative care when relevant and Tdap vaccination within the recommended window.

Weeks 32–35: growth and gradual preparation for birth

Fetal weight continues to rise and the brain and lungs continue maturing. Fetal presentation may become increasingly stable, although position can still change.

An ultrasound between weeks 30 and 34 may be used for medical indications such as placental location or other clinical needs.

Weeks 36–40: final preparation for birth

In the final weeks, fetal presentation becomes increasingly relevant, prenatal visits are closer together and preparation for labor becomes more practical.

There is no single week when every fetus completes development in exactly the same way. Gestational age and individual clinical assessment remain essential.

Fetal movement during the third trimester

Fetal movement is one of the most important changes that you can notice yourself during late pregnancy.

The character of movement can change as the fetus becomes larger, but a clear reduction in movement should not automatically be considered normal.

Become familiar with the usual movement pattern. Contact your maternity team if movement is clearly reduced or changes in a way that concerns you.

The 28-week prenatal visit

Week 28 is an important Saudi prenatal-care milestone and marks the beginning of trimester 3.

Care may include:

• Weight and blood-pressure measurement.
• Assessment of uterine growth.
• Fetal movement review.
• Fetal-heart assessment.
• Urine testing when indicated.
• Review of CBC, ferritin or glucose results as appropriate.
• Antibody testing and Anti-D planning for Rh-negative women when applicable.

Anti-D at around 28 weeks

If your blood group is Rh negative, your pregnancy plan may include Anti-D immunoglobulin around week 28, depending on your antibody status, history and local protocol.

Anti-D is not required for every pregnant woman, so the need cannot be determined from gestational age alone.

When is Tdap given during pregnancy?

The Saudi adult immunization schedule recommends Tdap during every pregnancy between weeks 27 and 36.

Vaccination helps protect the mother and allows protective antibodies, particularly against pertussis, to pass to the fetus before birth.

The 32-week prenatal visit

At around week 32, routine follow-up continues with blood pressure, weight, fetal movement, uterine growth and fetal-heart assessment.

New symptoms and pregnancy risk factors are also reviewed to decide whether closer monitoring is needed.

Do you need an ultrasound in the third trimester?

Not every pregnancy requires unlimited ultrasound examinations.

Saudi Ministry of Health guidance includes a possible third ultrasound between weeks 30 and 34 for medical indications, including placental location or other clinical reasons.

Depending on the situation, ultrasound may also assess fetal growth, amniotic fluid, placental position and fetal presentation.

Why is the 36-week visit important?

By week 36, preparation for birth becomes a central part of prenatal care.

Saudi guidance includes assessment of:

• Weight and blood pressure.
• Fetal movement.
• Uterine growth.
• Fetal heartbeat.
• Fetal presentation.
• Urine testing when needed.

Birth signs, breastfeeding, postpartum follow-up and preparation for hospital visits at weeks 38 and 40 are also discussed.

What is GBS screening and when is it performed?

Group B streptococcus, or GBS, is a bacterium that can naturally colonize the vaginal and rectal areas without causing illness.

Saudi Ministry of Health guidance recommends routine screening between weeks 36 and 37.

The test generally uses a vaginal and rectal swab. A positive result does not mean that the mother is ill or that the newborn will necessarily develop infection.

The result helps identify women who may need intravenous antibiotics during labor to reduce the risk of early newborn infection.

When does the fetus move into a head-down position?

Many fetuses gradually move into a head-down position as birth approaches.

Presentation can still change earlier in trimester 3, which is why assessment near week 36 is particularly useful for birth planning.

If the fetus is breech or in another presentation, the maternity team can discuss the available options based on gestational age and the individual pregnancy.

Braxton Hicks contractions versus true labor

Irregular tightening can occur during trimester 3 and may represent Braxton Hicks contractions.

They are often intermittent and do not steadily become stronger, closer together and more regular.

True labor more often develops a progressively regular pattern with increasing intensity and frequency.

No single rule can diagnose labor at home. Contact your maternity team if you are unsure, particularly before 37 weeks.

What are common signs that labor may be starting?

• Regular contractions that become stronger or closer together.
• Rupture of membranes or suspected water breaking.
• Mucus discharge that may contain a small amount of blood.
• Increasing pelvic pressure.
• Lower-back discomfort associated with regular contractions in some women.

Not every sign has to occur at the same time.

What should you do if your waters break?

If you notice a sudden gush or ongoing leakage of fluid that you cannot control, contact the maternity unit or your care team even if contractions have not started.

Note the time, color and odor of the fluid and avoid placing anything inside the vagina while awaiting assessment.

Labor before 37 weeks

Birth before 37 completed weeks is considered preterm.

During weeks 28–36, recurrent contractions, significant pelvic pressure, persistent unusual backache, a clear change in discharge or fluid leakage should be assessed.

Blood pressure and preeclampsia warning signs

Blood pressure continues to be checked during late-pregnancy visits because hypertension can be an important warning sign.

• Severe or persistent headache.
• Blurred or altered vision.
• Sudden or severe swelling of the face or hands.
• Severe or unusual upper-abdominal pain.
• Abnormally high blood-pressure readings when using a reliable home monitor.
• Significant general deterioration.

These symptoms do not diagnose preeclampsia, but they require medical assessment.

Swelling in late pregnancy

Swelling of the feet and ankles can occur as pregnancy progresses, especially after prolonged standing.

Sudden or severe swelling, particularly involving the face or hands or occurring with headache or visual changes, should be assessed.

Breathlessness, heartburn and frequent urination

The enlarging uterus can contribute to mild breathlessness, heartburn and more frequent urination.

Severe or sudden breathlessness, chest pain, fainting or marked palpitations should not be assumed to be a routine pregnancy symptom.

Sleep in the third trimester

Sleep can become more difficult because of the growing abdomen, fetal movement, heartburn and frequent urination.

Pillows can support the abdomen and back, while regular hydration during the day may reduce the need to drink large amounts immediately before sleep.

Preparing for birth before week 36

It is useful to make practical decisions before labor begins.

• Know the hospital or maternity unit you plan to use.
• Plan transport and a backup option.
• Decide who should be contacted when labor begins.
• Keep important medical documents and results accessible.
• Prepare a basic hospital bag.
• Discuss pain-relief options.
• Discuss breastfeeding and postpartum support.

A birth plan should remain flexible

A birth plan helps organize preferences and supports discussion with the maternity team, but it cannot guarantee that labor will follow a fixed sequence.

It may include preferences related to support people, pain relief, mobility, early skin-to-skin contact when appropriate, breastfeeding and important medical information.

What happens at the 38- and 40-week visits?

Saudi prenatal guidance places the final two follow-up visits at weeks 38 and 40 in hospital in preparation for birth.

Assessment focuses on maternal and fetal wellbeing, fetal movement, blood pressure, pregnancy progress, labor symptoms and any reason the birth plan may need to change.

Week 40 and no labor yet

The estimated due date is an estimate, not a guaranteed day for labor to begin.

Some women give birth before the estimated date and others after it. Once week 40 is reached, individualized follow-up becomes increasingly important.

Decisions about continued waiting or induction depend on accurate gestational age, fetal movement, maternal health, cervical findings, monitoring results and other pregnancy factors.

When should you seek prompt medical help?

• A clear reduction or concerning change in fetal movement.
• Vaginal bleeding.
• Fluid leakage or suspected rupture of membranes.
• Regular contractions before week 37.
• Severe persistent headache.
• Blurred or altered vision.
• Sudden or severe swelling of the face or hands.
• Severe or persistent abdominal pain.
• Fever or chills.
• Severe breathlessness, chest pain or fainting.
• Significant urinary burning or markedly reduced urine output.

Practical third-trimester checklist

1. Attend planned visits around weeks 28, 32, 36, 38 and 40.
2. Know the usual fetal movement pattern and report a clear reduction.
3. Ask about Tdap if it has not yet been given during this pregnancy.
4. If you are Rh negative, confirm the Anti-D plan.
5. Complete additional ultrasound when medically indicated.
6. Complete GBS screening around weeks 36–37 according to the care pathway.
7. Discuss fetal presentation and the birth plan near week 36.
8. Prepare transport, hospital documents and a basic hospital bag.
9. Know the signs of labor, rupture of membranes and pregnancy warning symptoms.
10. Discuss breastfeeding and postpartum follow-up before birth.

Third trimester week by week

• Week 28: trimester 3 begins and an important prenatal visit occurs.
• Week 29: continued growth and stronger movement.
• Week 30: the 30–34 week ultrasound window begins when medically indicated.
• Week 31: month 8 begins.
• Week 32: prenatal follow-up and ongoing fetal growth.
• Week 33: continued movement and growth monitoring.
• Week 34: approaching the end of the 30–34 ultrasound window.
• Week 35: preparation for late-pregnancy visits and birth planning.
• Week 36: month 9 begins, presentation assessment and GBS screening.
• Week 37: pregnancy is no longer within the preterm-birth definition.
• Week 38: hospital follow-up and preparation for birth.
• Week 39: monitor movement and signs of labor.
• Week 40: estimated due date and follow-up if labor has not begun.

From pregnancy to birth

The third trimester is the bridge between pregnancy follow-up and the birth journey.

As birth approaches, learning about labor signs, birth options, pain-relief choices, breastfeeding and the practical details of the maternity facility can help you prepare.

Medical basis for this guide

This guide follows Saudi Ministry of Health prenatal-care guidance, including visits at weeks 28, 32, 36, 38 and 40, medically indicated ultrasound around weeks 30–34, Tdap vaccination, late-pregnancy GBS screening, fetal-movement guidance and pregnancy warning signs.