Third Trimester Pregnancy: What to Expect Week by Week

Quick take: The third trimester (weeks 28‑40) is when your baby’s growth speeds up, your body prepares for birth, and you’ll notice new symptoms, weight‑gain targets, and prenatal visits. Most changes are normal, but watch for warning signs like intense contractions or bleeding. Stay nourished, move safely, and keep your care team in the loop.

It’s 10 p.m., you’re feeling a low‑back ache, a sudden craving for pickles, and a fluttering kick that feels louder than ever. You glance at the clock, wonder if the baby’s “dropping” already, and silently ask, “What’s supposed to happen now?” You’re not alone—most parents‑to‑be spend the last weeks of pregnancy navigating a flood of new sensations, appointments, and preparation tasks.

In this guide we’ll walk through every common question about the third trimester: the physical signs, how much weight you should still gain, what you’ll eat (and avoid), the schedule of prenatal visits, fetal growth milestones, safe exercise, sleep hacks, travel tips, and a checklist for the hospital bag. We’ll also flag the red‑flag symptoms that merit a call to your provider.

All recommendations reflect the latest guidance from the American College of Obstetricians and Gynecologists (ACOG), the UK’s National Health Service (NHS), and the World Health Organization (WHO). When in doubt, talk to your own clinician.

What are the common symptoms in the third trimester of pregnancy?

By the time you reach week 28, your body has been changing for months, and a new set of symptoms tends to appear. Knowing what’s typical helps you stay calm, and recognizing the outliers helps you know when to seek help.

Physical changes that most expectant parents notice

• Increasing belly size – The uterus expands to the rib cage, making breathing feel shallow.
• Shortness of breath – The growing uterus presses on the diaphragm; a gentle walk can improve lung capacity.
• Leg cramps and swelling – Fluid retention (edema) is common; elevate feet and stay hydrated.
• Back pain – Extra weight shifts your center of gravity; supportive shoes and prenatal‑safe stretches help.
• Frequent urination – The baby’s head presses on the bladder.
• Heartburn and indigestion – Hormonal relaxation of the lower esophageal sphincter lets acid rise.
• Fatigue – Hormones, anemia, and the extra effort of carrying a larger baby all contribute.

These sensations often overlap, and many women experience them in varying intensity. If any symptom feels unusually severe, or if you notice a sudden change, let your provider know—early conversation can rule out complications.

Third trimester cravings and aversions

Cravings for salty, sour, or sweet foods often intensify, while previously tolerated foods may suddenly become off‑putting. Hormonal fluctuations (especially estrogen and progesterone) alter taste buds. ACOG notes that cravings are harmless as long as you stay within your nutritional targets. Try to satisfy cravings with nutrient‑dense options—e.g., a handful of almonds for a salty urge or a sliced apple with peanut butter for sweetness.

When aversions make you nauseous, keep small, bland snacks on hand. A few crackers or a piece of toast can prevent a drop in blood sugar and keep you comfortable throughout the day.

Back pain and how to relieve it

Low‑back ache affects up to 70 % of third‑trimester moms. The best relief comes from a combination of posture, heat, and gentle movement. A prenatal‑safe routine—pelvic tilts, cat‑cow stretches, and side‑lying knee‑to‑chest—can ease tension. Applying a warm compress for 15 minutes before bedtime also reduces muscle spasms. If pain is sharp, constant, or accompanied by fever, call your provider.

Sleep problems and how to manage them

Finding a comfortable sleeping position is a major challenge. Most women eventually settle into the left‑side position, which optimizes blood flow to the placenta. Using a full‑length body pillow, placing a pillow between the knees, and keeping the bedroom cool (around 65 °F/18 °C) can improve sleep quality. If you’re waking frequently, limit caffeine after noon and practice a brief relaxation routine—deep breathing or a short guided meditation.

Sometimes night‑time leg cramps interrupt rest. Gentle stretching before bed and a magnesium‑rich snack (like a banana) can reduce their frequency, according to NHS recommendations.

Average baby size and when the baby drops

By week 36, the average baby weighs about 6 pounds (2.7 kg) and measures roughly 19 inches (48 cm) from crown to heel. The “baby drop” (lightening) usually occurs 2‑4 weeks before labor, when the head settles into the pelvis, relieving pressure on the diaphragm but increasing pelvic discomfort. If you notice a sudden shift in how the baby feels, it’s often a sign of lightening.

Lightening can make breathing easier, but it may also increase pressure on the bladder, leading to more frequent trips to the bathroom.

Fetal development milestones in the third trimester

These milestones reassure you that the baby’s organs are maturing, and they guide your provider’s timing for final ultrasounds and possible corticosteroid administration if early delivery becomes likely.

How much weight should I gain in the third trimester, and what nutrition guidelines should I follow?

Weight‑gain targets by BMI

Most of the weight is added in the third trimester as the baby, placenta, amniotic fluid, and maternal blood volume expand. If you’re gaining faster than these rates, discuss diet adjustments with your provider.

Nutrition basics

• Protein: Aim for 75‑100 g per day (≈½ lb of lean meat, beans, or tofu).
• Calcium: 1,000 mg daily—dairy, fortified plant milks, leafy greens.
• Iron: 27 mg daily—red meat, lentils, or prenatal iron supplement per ACOG.
• Fiber: 25‑30 g to reduce constipation.
• Omega‑3 DHA: 200‑300 mg for fetal brain development (fatty fish, algae supplements).

Limit added sugars and saturated fats, and stay within the recommended 300 mg of caffeine per day (≈2 cups of coffee). The NHS advises a daily intake of 2 ‑ 3 servings of fruit and 5 ‑ 6 servings of vegetables.

What foods should I avoid during the third trimester?

Some foods carry a higher risk of food‑borne illness or excess vitamin A, both of which can affect the baby.

Enjoy cooked eggs, well‑washed fruits, and pasteurized dairy without worry. If you’re craving a forbidden food, try a safe alternative—e.g., replace raw smoked salmon with smoked salmon that’s been fully cooked.

When should I schedule my third trimester prenatal appointments, and how often will I see my provider?

Regular check‑ups become more frequent as you near term. ACOG and the NHS recommend visits every 2 weeks until week 36, then weekly until delivery. Each appointment typically includes weight check, blood pressure, fetal heart rate monitoring, and a discussion of any new symptoms.

Key tests and screenings

• Growth ultrasounds (usually at 28‑32 weeks) to confirm fetal size and amniotic fluid volume.
• Group B Streptococcus (GBS) screening at 35‑37 weeks to determine need for intrapartum antibiotics.
• Non‑stress test (NST) if you have risk factors such as hypertension or decreased fetal movement.
• Blood tests for anemia, glucose tolerance (if not done earlier), and Rh‑factor management.

If you develop new concerns—persistent headaches, vision changes, swelling that doesn’t improve with elevation, or any bleeding—request an earlier appointment. Telehealth visits can address many questions without a full in‑person exam.

What to expect at each visit

During the 34‑week visit, your provider will likely assess fetal positioning and discuss signs of labor. By week 38, you’ll receive a final growth scan and a review of your birth plan. Understanding these steps can reduce anxiety and help you prepare for the day of delivery.

What foods should I avoid during the third trimester, and how can I manage cravings and aversions?

Beyond the high‑risk foods listed earlier, pay attention to portion size and nutrient density. Cravings often signal a need for a missing mineral (e.g., salt cravings may indicate low sodium due to fluid shifts). Pair cravings with healthy choices: a salty pretzel with a side of Greek yogurt, or a sweet fruit smoothie with added protein powder.

Tips for handling aversions

When a previously beloved food suddenly triggers nausea, try the following strategies:

1. Freeze the food in small portions and reheat only what you’ll eat.
2. Mask strong flavors with herbs, lemon juice, or mild sauces.
3. Eat the same nutrients from alternative sources—e.g., if you can’t tolerate dairy, choose fortified soy milk.

Maintain hydration—aim for 8‑10 cups of water daily. If you’re struggling to meet calorie goals, add nutrient‑dense smoothies or nut‑butter spreads.

How to prepare for labor and delivery in the third trimester, including a birth plan and hospital bag checklist?

Preparation starts now, not just the night before. A well‑thought‑out birth plan helps your care team understand your preferences, while a packed hospital bag reduces stress when the moment arrives.

Creating a birth plan

• Pain management: Indicate preferences for epidural, nitrous oxide, or natural coping techniques.
• Mobility: State whether you’d like to walk, use a birthing ball, or stay in bed.
• Delivery position: Choose from squatting, side‑lying, or hands‑and‑knees.
• Newborn care: Immediate skin‑to‑skin, delayed cord clamping, breastfeeding intentions.
• Support people: List who will be present (partner, doula, family).

Discuss your plan with your obstetrician at the 36‑week visit; they can advise on hospital policies and any medical contraindications.

Hospital bag checklist for the third trimester

Pack the bag by week 36 so you’re ready for a surprise early delivery.

What are the signs of preterm labor in the third trimester, and is it safe to have sex?

Preterm labor (before 37 weeks) is uncommon but serious. Early detection empowers you to seek care promptly.

Warning signs of preterm labor

• Regular contractions (every 5‑10 minutes) that persist for an hour.
• Change in vaginal discharge—especially watery, mucus‑like, or bloody fluid.
• Pelvic pressure that feels like “the baby is pushing down.”
• Lower‑back pain that’s constant or comes with cramping.
• Sudden increase in abdominal pain or a feeling of “tightening.”

If any of these occur, call your provider or go to the nearest labor‑and‑delivery unit. Early intervention (e.g., corticosteroids) can improve neonatal outcomes.

Sexual activity in the third trimester

For most uncomplicated pregnancies, ACOG states that vaginal intercourse is safe up to the onset of labor. Use a supportive pillow for comfort, and avoid deep penetration if the cervix feels soft or if you have a history of preterm labor. If you have placenta previa, a ruptured membrane, or are advised otherwise, abstain—your provider will let you know.

What exercises are safe in the third trimester of pregnancy, and how can I relieve back pain?

Staying active supports circulation, reduces swelling, and can make labor easier. However, certain activities become riskier as the uterus expands.

Recommended prenatal‑safe exercises

• Walking – Low impact, maintains cardiovascular health.
• Swimming or water aerobics – Buoyancy eases joint stress.
• Prenatal yoga – Focuses on gentle stretching and breathing.
• Modified strength training – Light dumbbells (≤5 lb) for upper‑body work.

Avoid contact sports, scuba diving, and exercises that involve lying flat on your back after week 20, as this can compress the vena cava and reduce blood flow.

Back‑pain relief through movement

Incorporate these three simple moves daily:

1. Pelvic tilt: Kneel on all fours, gently arch your back upward, then return to neutral. Repeat 10 times.
2. Side‑lying knee‑to‑chest: Lie on your left side, draw one knee toward your chest, hold 20 seconds, switch sides.
3. Standing hamstring stretch: Place one foot on a low step, keep the leg straight, lean forward slightly. Hold 30 seconds each side.

Heat pads, supportive maternity belts, and proper footwear also help. If pain is severe, persistent, or accompanied by fever, contact your provider.

How to manage sleep problems in the third trimester and travel safety tips?

Restful sleep often feels like a distant memory, but a few adjustments can make a big difference. If you’re planning travel, a few extra precautions will keep you comfortable and safe.

Sleep‑hygiene tips for the final weeks

• Establish a bedtime routine—warm shower, light stretching, and a short meditation.
• Use a body pillow to keep the hips aligned and reduce pressure on the lower back.
• Limit fluids 1 hour before bed to reduce nighttime bathroom trips.
• Keep the bedroom cool and dark; consider a white‑noise machine.
• Avoid caffeine after 2 p.m. and limit nicotine or alcohol, which disrupt sleep cycles.

Travel safety in the third trimester

Most airlines allow travel up to 36 weeks for domestic flights and 32 weeks for international trips, but policies vary. Bring a copy of your prenatal records, stay hydrated, and move your legs every 30 minutes to prevent deep‑vein thrombosis (DVT). If you’re traveling by car, stop every 2 hours to stretch.

For long trips, pack snacks that meet your nutritional goals—nuts, cheese sticks, and fruit—so you can avoid unhealthy airport fare. If you have a high‑risk pregnancy (e.g., preeclampsia), discuss travel plans with your provider before you book.

Managing swelling and varicose veins in the third trimester

Edema, especially in the feet, ankles, and hands, is common as fluid pools in lower extremities. The NHS advises elevating your legs above heart level for 15 minutes a few times a day and wearing loose‑fitting clothing to improve circulation.

Compression stockings (support level 15‑20 mmHg) can reduce swelling and prevent varicose veins, a recommendation supported by ACOG. Gentle calf‑muscle pumps—like flexing and pointing your toes while seated—also encourage venous return. If swelling becomes sudden, painful, or accompanied by shortness of breath, seek medical evaluation promptly.

Understanding third trimester prenatal testing and screenings

Beyond the routine visits, several optional tests can provide insight into fetal health. The non‑invasive prenatal test (NIPT) analyzes cell‑free DNA in maternal blood to screen for chromosomal conditions such as Down syndrome. ACOG notes that NIPT can be performed as early as 10 weeks, but many choose to confirm results with an amniocentesis later in the third trimester if indicated.

Amniocentesis, typically offered after 15 weeks, samples amniotic fluid for detailed genetic analysis. While the procedure carries a small risk of miscarriage (≈0.1‑0.3 %), it can guide critical decisions for families with a history of genetic disorders. Discuss the benefits and risks with your provider to determine if it’s right for you.

From our medical team: The third trimester feels like a marathon, but you’ve built stamina with every prenatal visit. Trust your body’s signals, keep hydrated, move gently, and keep your care team in the loop. Most of the symptoms you’re experiencing are normal, and the majority of pregnancies progress smoothly to a healthy birth.

Myth vs. fact

Myth: You must gain at least 30 pounds in the third trimester.

Fact: Weight‑gain recommendations depend on pre‑pregnancy BMI; a normal‑weight woman typically gains 0.5‑1 lb per week, not a fixed total.

Myth: All cravings are dangerous and should be avoided.

Fact: Cravings are usually harmless; the key is to satisfy them with nutrient‑dense foods and keep overall calorie intake within recommended limits.

Myth: You can’t have sex after week 30.

Fact: For uncomplicated pregnancies, sexual activity is safe until labor begins; always follow your provider’s specific advice.

Key takeaways

• Typical third‑trimester symptoms include shortness of breath, back pain, cravings, and sleep disturbances—most are normal.
• Aim for a steady weight‑gain rate based on your pre‑pregnancy BMI; use the provided table as a guide.
• Schedule prenatal visits every 2 weeks until 36 weeks, then weekly until delivery; expect growth ultrasounds and GBS screening.
• Avoid unpasteurized cheeses, raw seafood, deli meats, high‑mercury fish, and excess vitamin A.
• Prepare a birth plan and pack a hospital bag by week 36 to reduce last‑minute stress.
• Safe exercises include walking, swimming, and prenatal yoga; incorporate daily back‑pain stretches.
• Use a left‑side sleeping position, pillows, and a cool bedroom to improve sleep; limit caffeine after noon.
• Watch for preterm‑labor signs—regular contractions, fluid loss, or persistent back pain—and call your provider immediately.
• Compression stockings and leg elevation can ease swelling; discuss any sudden or painful edema with your clinician.
• Optional testing like NIPT or amniocentesis provides additional genetic insight; weigh benefits and risks with your care team.

Frequently asked questions

What are the signs that my third trimester is progressing normally?

A normal progression includes steady weight gain, regular fetal movements, occasional Braxton‑Hicks contractions, and a gradual increase in belly size without severe pain or bleeding.

How often should I see my doctor during the third trimester?

Most guidelines recommend visits every 2 weeks until week 36, then weekly until delivery, with each appointment checking blood pressure, weight, fetal heart rate, and symptom review.

When will I feel the baby move the most in the third trimester?

Fetal movements peak between weeks 32‑36, often described as strong kicks or rolls; if you notice a sudden decrease in movement, contact your provider right away.

Is it safe to have sex during the third trimester?

For uncomplicated pregnancies, sex is generally safe up to labor; avoid deep penetration if your cervix feels soft or if you have a high‑risk condition like placenta previa.

What foods should I avoid in the third trimester?

Avoid unpasteurized soft cheeses, raw or undercooked seafood, cold deli meats, high‑mercury fish, and excess vitamin A (e.g., liver pâté); these can pose infection or toxicity risks.

How can I tell if I am going into labor early in the third trimester?

Early labor signs include regular, painful contractions (every 5‑10 minutes), a change in vaginal discharge, pelvic pressure, and lower‑back pain that doesn’t ease with rest; seek immediate medical attention if these appear.

Can I travel internationally after 32 weeks?

Many airlines restrict international travel after 32 weeks, but policies vary; check with your carrier and confirm with your provider. If cleared, stay hydrated, move every 30 minutes, and carry your prenatal records.

Should I start breastfeeding preparation now?

Yes—most lactation experts recommend beginning breast‑feeding education in the third trimester. Simple steps like practicing hand‑expressing milk, researching latch techniques, and arranging a postpartum lactation consult can boost confidence once baby arrives.

When to call your doctor

Contact your provider right away if you experience any of the following: heavy bleeding, sudden gush of fluid, persistent severe abdominal pain, fever ≥ 100.4 °F (38 °C), a rapid increase in swelling, or a noticeable decrease in fetal movement. This article is for informational purposes only and does not replace personalized medical advice.

References

1. American College of Obstetricians and Gynecologists (ACOG). “Weight Gain During Pregnancy.” 2023 clinical guidance.
2. National Health Service (NHS). “Pregnancy: what to expect in the third trimester.” Updated 2022.
3. World Health Organization (WHO). “Nutrition for pregnant women.” 2021 recommendations.
4. Centers for Disease Control and Prevention (CDC). “Listeria and pregnancy.” 2022 guidance.
5. Society for Maternal-Fetal Medicine (SMFM). “Guidelines for prenatal care.” 2023.
6. Royal College of Obstetricians and Gynaecologists (RCOG). “Management of preterm labor.” 2022.
7. American Academy of Pediatrics (AAP). “Safe travel during pregnancy.” 2021.
8. National Institute for Health and Care Excellence (NICE). “Antenatal care guidelines.” 2023.
9. American College of Obstetricians and Gynecologists (ACOG). “Non‑invasive prenatal testing (NIPT) and amniocentesis.” 2022.
10. Food and Drug Administration (FDA). “Compression Stockings for Pregnancy.” 2021 safety bulletin.