Third Trimester: Weeks 28-40 Preparing for Birth and Final Changes

The third trimester marks the final stretch of your pregnancy journey, spanning from week 28 until delivery. This period brings a mixture of excitement, anticipation, and perhaps some anxiety as you prepare to meet your baby. According to obstetric guidelines, the third trimester encompasses crucial fetal development, with your baby gaining most of their birth weight and their organs completing maturation. For expecting parents, these weeks involve intense physical changes, final preparations, and increasing awareness that labor could begin at any time after 37 weeks. Understanding what to expect during this trimester helps you navigate the challenges while celebrating the approaching arrival of your little one. This comprehensive guide covers everything from week-by-week development to birth preparation, ensuring you feel confident and prepared for these final pregnancy weeks.

What's Happening to Your Body During Weeks 28-40

The third trimester brings the most dramatic physical changes as your body prepares for labor and delivery. Your uterus expands from the size of a soccer ball to a watermelon, accommodating your rapidly growing baby. This growth affects nearly every system in your body, creating new symptoms while intensifying others.

Your cardiovascular system works at maximum capacity during the third trimester. Blood volume peaks at 40-50% above pre-pregnancy levels, and your heart pumps 30-50% more blood per minute. This increased workload may cause palpitations, shortness of breath, and swelling in your extremities. The growing uterus compresses major blood vessels when you lie on your back, potentially causing dizziness or nausea - a condition called supine hypotensive syndrome.

Respiratory changes become more pronounced as your expanding uterus pushes against your diaphragm, reducing lung capacity by up to 20%. Despite this compression, your body compensates by breathing more efficiently, ensuring adequate oxygen for you and baby. Many women experience breathlessness during simple activities like climbing stairs or walking. This "air hunger" is normal but can be distressing.

Your musculoskeletal system bears increasing strain. The hormone relaxin continues loosening joints and ligaments, particularly in your pelvis, preparing for delivery. Combined with your shifted center of gravity and additional weight (typically 25-35 pounds by term), this creates significant stress on your back, hips, and pelvis. Many women develop a characteristic "pregnancy waddle" as their body adapts to these changes.

Digestive system challenges intensify during the third trimester. Your growing uterus compresses your stomach and intestines, reducing capacity and slowing digestion. Heartburn affects up to 80% of pregnant women by the third trimester as stomach acid refluxes into the esophagus. Constipation worsens due to progesterone's effects and physical compression of the intestines.

Skin changes reach their peak during these final weeks. Stretch marks may appear or darken on your abdomen, breasts, hips, and thighs as skin rapidly expands. The linea nigra becomes more prominent, and some women develop PUPPP (pruritic urticarial papules and plaques of pregnancy), an intensely itchy rash. Increased blood flow may cause spider veins, varicose veins, and hemorrhoids.

Your urinary system faces mounting pressure. The growing uterus compresses your bladder, reducing capacity and causing frequent urination - sometimes every hour. Stress incontinence (leaking urine when coughing, sneezing, or laughing) affects many women due to weakened pelvic floor muscles. The ureters dilate under hormonal influence, slightly increasing urinary tract infection risk.

Sleep becomes increasingly elusive during the third trimester. Physical discomfort, frequent urination, leg cramps, and anxiety about impending labor contribute to insomnia. Finding comfortable positions grows challenging as your belly expands. Many women experience vivid dreams or nightmares about labor and parenthood, reflecting subconscious processing of this major life transition.

Braxton Hicks contractions increase in frequency and intensity, sometimes called "practice contractions." These irregular tightenings prepare your uterus for labor but don't cause cervical changes. Distinguishing between Braxton Hicks and true labor becomes important as you approach your due date.

Your Baby's Development During the Third Trimester

The third trimester transforms your baby from a tiny, fragile being into a fully developed infant ready for life outside the womb. This period focuses on growth, organ maturation, and preparation for birth.

Week 28: Your baby weighs approximately 2.25 pounds and measures 14.8 inches. The eyes can open and close, responding to light filtered through your abdomen. Brain development accelerates with billions of neurons forming complex connections. Breathing movements become more regular as lungs continue maturing. Week 29: At about 2.5 pounds and 15.2 inches, your baby's muscles and bones continue strengthening. The head grows to accommodate rapid brain development. Baby begins storing iron, calcium, and phosphorus for use after birth. Movement patterns become more predictable with distinct wake-sleep cycles. Week 30: Weighing approximately 2.9 pounds and measuring 15.7 inches, your baby's bone marrow takes over red blood cell production from the spleen. The digestive tract nears maturity, preparing to process milk after birth. Lanugo begins disappearing as fat deposits provide temperature regulation. Week 31: Your baby reaches about 3.3 pounds and 16.2 inches. Brain development enables temperature regulation, though assistance is still needed after birth. Eyes can track light, and pupils dilate and constrict. Fingernails reach fingertips, possibly requiring trimming at birth. Week 32: At approximately 3.75 pounds and 16.7 inches, your baby's skeleton hardens, though skull bones remain flexible for delivery. Toenails reach toe tips. Practice breathing increases, strengthening respiratory muscles. The digestive system is nearly mature. Week 33: Weighing about 4.2 pounds and measuring 17.2 inches, your baby's brain continues rapid development. The immune system strengthens through antibodies transferred from you. Vernix caseosa thickens, protecting delicate skin. Baby may settle into head-down position. Week 34: Your baby reaches approximately 4.7 pounds and 17.7 inches. Lung development accelerates with increased surfactant production. Central nervous system and lungs continue maturing. If born now, your baby would likely need minimal medical intervention. Week 35: At about 5.3 pounds and 18 inches, your baby's kidneys are fully developed. Liver function matures, processing waste products. Most babies assume head-down position by this week. Physical features are fully developed, resembling a newborn. Week 36: Weighing approximately 5.8 pounds and measuring 18.5 inches, your baby is considered "early term." Digestive system is ready to process breast milk or formula. Circulation and immune systems function independently. Baby "drops" into pelvis (lightening) in preparation for birth. Week 37: Your baby reaches about 6.3 pounds and 19 inches. Officially full-term, all organs function independently. Lungs are mature enough to breathe air. Practice breathing, sucking, and swallowing continue. Head circumference roughly equals abdominal circumference. Week 38: At approximately 6.8 pounds and 19.5 inches, your baby's brain and nervous system continue fine-tuning. Grip strength increases - strong enough to grasp your finger at birth. Meconium accumulates in intestines. Eye color may change after birth as pigmentation develops. Week 39: Weighing about 7.3 pounds and measuring 20 inches, your baby is fully developed and ready for birth. Fat continues accumulating, providing energy reserves and temperature regulation. Chest movements mimic breathing. Vernix and lanugo mostly disappear except in skin creases. Week 40: At an average of 7.5 pounds and 20.2 inches, your baby has reached their due date. Only 5% of babies arrive exactly on their due date. Placenta begins aging but continues functioning. Baby's movements may decrease due to limited space but should remain regular. Weeks 41-42: Post-term babies continue gaining weight, averaging 8-9 pounds. Vernix decreases, potentially causing dry, peeling skin at birth. Placental function may decline, requiring monitoring. Most providers recommend induction by 42 weeks to prevent complications.

Common Third Trimester Symptoms and Management Strategies

The third trimester brings intensified symptoms requiring active management for comfort and health. Understanding these challenges and relief strategies helps you cope during these final weeks.

Shortness of Breath affects most women as the uterus compresses the diaphragm. Management includes practicing good posture to maximize lung space, sleeping propped on pillows, taking frequent breaks during activities, using breathing exercises from childbirth classes, and avoiding overexertion. Contact your provider if breathlessness is severe or accompanied by chest pain. Back Pain and Pelvic Pressure intensify with increased weight and loosened ligaments. Relief strategies include prenatal massage or chiropractic care, warm baths (not too hot), prenatal yoga or stretching, proper body mechanics when lifting, supportive shoes, pregnancy support belts, and sleeping with pillow support. Swelling (Edema) commonly affects feet, ankles, and hands due to increased fluid retention and compressed blood vessels. Management involves elevating feet when sitting, staying hydrated, limiting sodium intake, wearing compression socks, avoiding prolonged standing, exercising regularly to promote circulation, and sleeping on your left side. Sudden or severe swelling requires immediate medical attention as it may indicate preeclampsia. Heartburn and Indigestion peak during the third trimester. Relief includes eating small, frequent meals, avoiding trigger foods (spicy, fatty, acidic), remaining upright after eating, sleeping with head elevated, trying natural remedies like papaya enzymes, using antacids approved by your provider, and avoiding eating close to bedtime. Insomnia and Fatigue create a challenging cycle. Improve sleep by establishing consistent bedtime routines, limiting fluids before bed, using pregnancy pillows for support, keeping bedroom cool and dark, practicing relaxation techniques, napping briefly during daytime, and avoiding screens before bed. Frequent Urination and Incontinence worsen as baby drops into pelvis. Management includes doing Kegel exercises regularly, emptying bladder completely when urinating, wearing panty liners for security, avoiding bladder irritants like caffeine, maintaining healthy weight gain, and discussing persistent problems with your provider. Hemorrhoids and Constipation result from increased pressure and slowed digestion. Prevention and treatment include increasing fiber intake gradually, staying well-hydrated, exercising regularly, avoiding straining, using witch hazel pads for relief, trying sitz baths, and discussing safe stool softeners with your provider. Leg Cramps and Restless Legs often disrupt sleep. Relief strategies include stretching calves before bed, staying hydrated, ensuring adequate calcium and magnesium intake, wearing supportive shoes, massaging affected muscles, applying heat to cramped areas, and flexing feet upward during cramps.

When to Contact Your Healthcare Provider in the Third Trimester

Understanding warning signs becomes crucial as you approach delivery. While many symptoms are normal, certain conditions require immediate attention.

Call 911 or go to emergency room immediately for:

- Heavy vaginal bleeding (soaking pad in an hour) - Severe abdominal pain - Chest pain or difficulty breathing - Seizures - Loss of consciousness - Thoughts of harming yourself or baby

Contact your provider immediately for:

- Regular contractions before 37 weeks (preterm labor) - Decreased fetal movement - Leaking fluid (possible ruptured membranes) - Severe headache unrelieved by rest/hydration - Vision changes (blurriness, spots, flashing lights) - Sudden swelling of face or hands - Persistent vomiting - Fever over 100.4°F - Signs of labor after 37 weeks

Report within 24 hours:

- Mild contractions that don't progress - Increased vaginal discharge - Persistent backache - Unusual fatigue or weakness - Anxiety or depression symptoms - Questions about labor signs

Partner Support During the Third Trimester

Partners play crucial roles during these final pregnancy weeks, providing physical assistance, emotional support, and practical preparation for baby's arrival.

Physical Support: Help your pregnant partner with daily tasks that become challenging. Tie shoes, pick up dropped items, assist getting in/out of bed or car. Provide foot rubs, back massages, or help apply lotion to unreachable areas. Accompany walks for exercise and support. Prepare meals considering dietary restrictions and aversions. Emotional Support: Acknowledge the physical and emotional challenges of late pregnancy. Listen to concerns about labor, parenting, and body changes without minimizing feelings. Reassure about your commitment and excitement. Discuss fears openly - you likely share many concerns. Celebrate milestones like reaching full term. Birth Preparation: Attend childbirth classes together, practicing breathing techniques and comfort measures. Discuss birth preferences and create birth plan together. Learn about labor stages and when to go to hospital. Practice routes to hospital at different times. Pack hospital bags together. Install car seat and have it inspected. Practical Preparations: Finalize nursery setup and baby essentials. Deep clean house before baby arrives. Prepare meals for freezer. Arrange pet care for hospital stay. Update emergency contacts. Ensure work coverage plans. Handle paperwork like pre-registration and insurance updates. Communication: Discuss expectations for labor support. Learn your partner's preferences for comfort measures. Understand when they want advocacy versus space. Plan communication with family during labor. Agree on visitor policies for hospital and home. Self-Care: Maintain your own health to be strong support. Process your emotions about becoming a parent. Connect with other expectant or new parents. Prepare for your own life changes. Consider taking time off work around due date.

Preparing for Labor and Delivery

The third trimester focuses heavily on birth preparation. Creating comprehensive plans while remaining flexible helps you feel confident approaching labor.

Birth Plan Creation: Discuss preferences with your healthcare provider, understanding which aspects are flexible. Consider pain management preferences, labor positions, immediate postpartum procedures, and newborn care choices. Write plans clearly but stay adaptable - labor rarely follows exact plans. Hospital Bag Packing: Pack by 36 weeks in case of early labor. Include comfortable labor clothes, going-home outfits for you and baby, toiletries, important documents, camera, phone chargers, snacks for partner, entertainment for early labor, and comfort items from home. Labor Recognition: Learn differences between true and false labor. True labor contractions grow stronger, longer, and closer together. They don't stop with position changes or hydration. You may experience bloody show, water breaking, or intense pelvic pressure. Time contractions using apps or traditional methods. Comfort Measures: Practice various pain management techniques including breathing patterns, visualization, position changes, hydrotherapy, massage, and counterpressure. Understand medication options like epidurals, discussing risks and benefits with providers. Final Preparations: Complete nursery setup with essentials accessible. Wash baby clothes and bedding in fragrance-free detergent. Stock home with postpartum supplies. Arrange newborn photography if desired. Finalize name choices. Prepare birth announcements.

Frequently Asked Questions About the Third Trimester

Q: How do I count fetal movements?

A: Choose a time when baby is typically active. Count movements until reaching 10, noting time elapsed. Most babies produce 10 movements within 2 hours. Report significant changes in pattern to your provider.

Q: When should I stop working?

A: This varies individually based on job demands, pregnancy complications, and personal comfort. Some work until labor begins; others stop weeks earlier. Discuss with your provider and employer to determine best timing.

Q: Are third trimester ultrasounds necessary?

A: Routine third trimester ultrasounds aren't always required for low-risk pregnancies. Providers may order them to check growth, fluid levels, or position. Follow your provider's recommendations based on your circumstances.

Q: How can I naturally induce labor?

A: While many methods exist (walking, spicy food, intercourse), limited evidence supports effectiveness. Never attempt induction without provider approval. Some methods like castor oil can be dangerous. Trust your body's timing unless medical induction is necessary.

Q: What's the mucus plug?

A: The mucus plug seals your cervix during pregnancy. Its loss (appearing as thick discharge, possibly blood-tinged) can occur weeks before labor or during early labor. It's normal but doesn't necessarily mean immediate labor.

Q: Should I be worried about decreased movement?

A: Babies have less room to move dramatically but should maintain regular patterns. You should still feel movement throughout the day. Any significant decrease warrants immediate evaluation.

Q: When do most first-time mothers deliver?

A: First-time mothers often deliver slightly past their due date, with average around 40 weeks + 5 days. However, normal term delivery ranges from 37-42 weeks.

Q: Can I prevent stretch marks?

A: While genetics largely determine stretch mark development, keeping skin moisturized and maintaining steady weight gain may help minimize them. No product guarantees prevention.

Q: Is nesting real?

A: Yes, many women experience intense urges to clean and organize before baby's arrival. This instinct helps prepare your environment but avoid overexertion.

Q: What if my baby is breech?

A: Approximately 3-4% of babies remain breech at term. Options include external cephalic version (manually turning baby), specific exercises, or planned cesarean delivery. Discuss options with your provider.

Quick Reference: Third Trimester Checklist

Weeks 28-32:

- Begin childbirth classes - Tour birthing facility - Create birth plan draft - Start kick counting - Interview pediatricians - Review maternity leave

Weeks 33-36:

- Pack hospital bags - Install car seat - Finalize nursery - Pre-register at hospital - Arrange postpartum help - Stock freezer meals

Weeks 37-40:

- Review labor signs - Finalize baby names - Confirm on-call arrangements - Practice hospital route - Rest and conserve energy - Enjoy final preparations

Labor Warning Signs:

- Regular contractions 5 minutes apart - Water breaking - Heavy bleeding - Severe pain - Decreased movement

The third trimester culminates your pregnancy journey with anticipation, preparation, and transformation. While physical challenges intensify, remember each discomfort brings you closer to meeting your baby. Trust your body's incredible ability to nurture and deliver new life. Maintain open communication with your healthcare team, prepare thoughtfully but flexibly for birth, and don't hesitate seeking support when needed. Soon, these challenging weeks will fade as you embrace the joy of holding your newborn. Your strength during this final trimester prepares you for the amazing journey of parenthood ahead.