Third Trimester Physiological Changes and Discomforts
Education and Management Strategies for Nursing Practice
Table of Contents
- Introduction to Third Trimester
- Cardiovascular System Changes
- Respiratory System Changes
- Gastrointestinal System Changes
- Musculoskeletal System Changes
- Urinary System Changes
- Integumentary System Changes
- Neurological and Psychological Changes
- Nursing Assessment in Third Trimester
- Best Practices for Patient Education
- New Nursing Updates for Third Trimester Care
- References
Introduction to Third Trimester
The third trimester spans from week 28 until delivery (approximately week 40) and represents the culmination of pregnancy. During this period, the fetus experiences significant growth and development while the maternal body undergoes profound physiological adaptations to support both the mother and the developing baby. Understanding these third trimester physiological changes is crucial for nursing professionals to provide appropriate education and care to pregnant individuals.
This critical period is characterized by numerous physiological changes across multiple body systems that can cause various discomforts. As nursing professionals, our role involves not only recognizing these changes but also providing evidence-based education and management strategies to enhance maternal comfort and ensure positive outcomes.
Key Third Trimester Statistics:
- Duration: Weeks 28-40 (or until delivery)
- Average fetal weight gain: 2-3 pounds per month
- Average maternal weight gain: 0.5-1 pound per week
- Total blood volume increase: 40-50% above pre-pregnancy levels
- Cardiac output: 30-50% above pre-pregnancy levels
Cardiovascular System Changes
Physiological Changes
- Blood volume increases by 40-50% compared to pre-pregnancy levels
- Heart rate increases by 15-20 beats per minute
- Cardiac output increases by 30-50% (peaks at 32-34 weeks)
- Systemic vascular resistance decreases
- Supine hypotensive syndrome can occur due to compression of inferior vena cava by the enlarged uterus
- Blood pressure may decrease initially but returns to normal by term
- Development of physiologic heart murmurs in over 90% of pregnant women
Common Discomforts
- Dizziness and syncope (especially in supine position)
- Dependent edema (particularly in ankles and feet)
- Varicose veins (legs, vulva)
- Palpitations
- Orthostatic hypotension
Management Strategies
- Position changes: Advise to avoid prolonged standing and lying flat on back; recommend left lateral position when resting
- Graduated compression stockings: Recommend wearing during the day to reduce varicose veins and edema
- Adequate hydration: Maintain 8-10 glasses of water daily to support increased blood volume
- Physical activity: Encourage regular moderate exercise to improve circulation
- Elevation: Suggest elevating legs above heart level several times daily to reduce dependent edema
Warning Signs to Report
Educate patients to report immediately:
- Severe headache with visual changes
- Sudden swelling of face, hands, or feet that doesn’t resolve with rest
- Heart palpitations that persist at rest
- Chest pain or difficulty breathing
- Signs of deep vein thrombosis (unilateral leg pain, swelling, redness)
Respiratory System Changes
Physiological Changes
- Diaphragm elevates 4-5 cm due to enlarging uterus
- Thoracic breathing predominates over abdominal breathing
- Oxygen consumption increases by 20-30%
- Tidal volume increases by 30-40%
- Respiratory rate increases slightly
- Nasal mucosa becomes edematous and hyperemic due to increased estrogen
- Mild compensated respiratory alkalosis (decreased PaCO₂)
Common Discomforts
- Dyspnea (shortness of breath), especially with exertion
- Nasal congestion and epistaxis (nosebleeds)
- Sleep-disordered breathing/snoring
- Decreased exercise tolerance
Management Strategies
- Proper posture: Encourage good posture to maximize lung expansion
- Position changes: Suggest semi-Fowler’s position (elevated head of bed) for sleeping
- Pacing activities: Recommend dividing activities into smaller tasks with rest periods
- Nasal saline: Advise saline nasal sprays for congestion
- Humidifier: Suggest using during sleep to decrease dryness and congestion
- Breathing techniques: Teach pursed-lip breathing for episodes of breathlessness
Warning Signs to Report
Educate patients to report immediately:
- Severe shortness of breath at rest
- Inability to complete sentences without pausing for breath
- Chest pain with breathing
- Persistent cough, especially with sputum production
- Signs of respiratory infection (fever, colored discharge)
Gastrointestinal System Changes
Physiological Changes
- Decreased gastric motility and intestinal transit time due to progesterone
- Displacement of stomach and intestines by enlarging uterus
- Relaxation of lower esophageal sphincter
- Increased intragastric pressure
- Decreased gallbladder contractility
- Increased water absorption from colon
- Gingival hyperemia and inflammation due to hormonal changes
Common Discomforts
- Heartburn/gastroesophageal reflux (worsens in third trimester)
- Constipation
- Hemorrhoids
- Feeling of fullness after eating small amounts
- Gingival bleeding and dental issues
Management Strategies
- For heartburn:
- Eat small, frequent meals instead of large meals
- Avoid spicy, fatty, and acidic foods
- Remain upright for 1-2 hours after eating
- Use approved antacids as recommended by healthcare provider
- For constipation:
- Increase dietary fiber intake (25-30g daily)
- Maintain adequate hydration (8-10 glasses of water daily)
- Regular physical activity
- Consider approved stool softeners if dietary changes are insufficient
- For hemorrhoids:
- Avoid straining during bowel movements
- Apply cold packs to reduce swelling
- Warm sitz baths for comfort
- Use topical treatments as recommended by healthcare provider
Best Dietary Practices
- Encourage regular small meals (5-6 per day)
- Emphasize high-fiber foods (whole grains, fruits, vegetables)
- Suggest drinking fluids between meals rather than with meals to reduce fullness
- Avoid lying down immediately after eating
- Maintain good oral hygiene with regular brushing and flossing
Musculoskeletal System Changes
Physiological Changes
- Relaxation of ligaments and joints due to relaxin hormone
- Anterior pelvic tilt to accommodate enlarging uterus
- Progressive lordosis (exaggerated curvature of the lumbar spine)
- Widening and increased mobility of the pubic symphysis
- Center of gravity shifts forward
- Stretched abdominal muscles (rectus abdominis)
- Weight gain places increased pressure on weight-bearing joints
Common Discomforts
- Low back pain (affects up to 70% of pregnant women)
- Pelvic girdle pain
- Round ligament pain
- Leg cramps, particularly at night
- Joint pain, especially in knees and hips
- Carpal tunnel syndrome (due to fluid retention)
Management Strategies
- For back pain:
- Use proper body mechanics when lifting (bend knees, not waist)
- Wear supportive shoes with low heels
- Use maternity support belt to distribute weight
- Apply heat to sore areas
- Practice gentle stretching exercises
- Consider prenatal massage therapy
- For leg cramps:
- Stretch calf muscles before bed
- Ensure adequate calcium and magnesium intake
- Stay hydrated
- Apply heat to affected muscles
- For carpal tunnel syndrome:
- Wrist splints, especially at night
- Hand and wrist exercises
- Elevate hands and arms when possible
Recommended Exercises
- Pelvic tilts: To strengthen abdominal muscles and reduce back strain
- Kegel exercises: To strengthen pelvic floor muscles
- Swimming: Provides buoyancy and reduces joint stress
- Prenatal yoga: Improves flexibility and promotes relaxation
- Gentle walking: Maintains general conditioning
Note: Always advise patients to consult with their healthcare provider before starting any exercise program.
Urinary System Changes
Physiological Changes
- Increased renal plasma flow by 50-80%
- Glomerular filtration rate increases by 40-65%
- Dilation of the renal pelvis and ureters due to progesterone effects and mechanical compression
- Bladder capacity decreases as uterus grows
- Decreased bladder tone due to hormonal effects
- Increased pressure on bladder from enlarging uterus
- Glycosuria may occur due to decreased renal threshold for glucose
Common Discomforts
- Increased urinary frequency (returns or worsens in third trimester)
- Urgency
- Nocturia (nighttime urination)
- Stress incontinence
- Increased risk of urinary tract infections
Management Strategies
- For urinary frequency:
- Maintain adequate hydration during the day
- Reduce fluid intake in the evening to minimize nocturia
- Urinate when feeling the urge (don’t delay voiding)
- Double void (urinate, wait a few moments, then try again)
- For stress incontinence:
- Regular pelvic floor exercises (Kegels)
- Use panty liners if needed
- Empty bladder before physical activity
- For UTI prevention:
- Maintain adequate hydration
- Empty bladder completely when urinating
- Urinate before and after sexual activity
- Wipe from front to back
- Wear cotton underwear
Warning Signs to Report
Educate patients to report immediately:
- Burning or pain during urination
- Cloudy or foul-smelling urine
- Blood in urine
- Fever and/or chills
- Flank pain (may indicate pyelonephritis)
- Decreased urinary output
Integumentary System Changes
Physiological Changes
- Increased melanocyte-stimulating hormone activity
- Increased sebaceous gland activity
- Increased blood flow to the skin
- Connective tissue changes from hormonal influences
- Increased sweat gland activity
- Vascular changes throughout the skin
Common Discomforts
- Striae gravidarum (stretch marks)
- Hyperpigmentation (melasma/chloasma, linea nigra)
- Pruritus (itching), especially on abdomen
- Heat intolerance and increased sweating
- Spider nevi and palmar erythema
- Skin tags
- Changes in hair growth and texture
Management Strategies
- For stretch marks:
- Regular moisturizing of skin (though evidence for prevention is limited)
- Gradual weight gain throughout pregnancy
- Education about normal skin changes
- For pruritus:
- Avoid hot showers/baths (use lukewarm water)
- Use mild, fragrance-free soaps
- Apply unscented moisturizer to damp skin
- Wear loose-fitting cotton clothing
- Colloidal oatmeal baths for relief
- For hyperpigmentation:
- Sun protection (SPF 30+ sunscreen, wide-brimmed hats)
- Education that most changes will fade postpartum
- For heat intolerance:
- Lightweight, loose clothing
- Stay in climate-controlled environments when possible
- Cool baths or showers
- Adequate hydration
Warning Signs to Report
Educate patients to report:
- Severe itching without rash (may indicate cholestasis of pregnancy)
- Rashes that are widespread or accompanied by other symptoms
- New moles or significant changes in existing moles
- Yellow discoloration of skin (jaundice)
Neurological and Psychological Changes
Physiological Changes
- Altered sleep patterns due to physical discomfort
- Hormonal influence on mood and cognitive function
- Increased intracranial pressure due to increased blood volume
- Compression of peripheral nerves (e.g., carpal tunnel, meralgia paresthetica)
- Changes in sense of taste and smell
- Alterations in memory and concentration (“pregnancy brain”)
Common Discomforts
- Sleep disturbances and insomnia
- Increased anxiety about labor, delivery, and parenting
- Mood swings
- Vivid dreams
- Fatigue
- Memory changes and difficulty concentrating
- Headaches
Management Strategies
- For sleep disturbances:
- Use supportive pillows (especially pregnancy pillow)
- Establish relaxing bedtime routine
- Limit screen time before bed
- Sleep on left side with pillow between knees
- Avoid caffeine in the afternoon/evening
- For anxiety:
- Encourage participation in childbirth education classes
- Promote connection with support systems
- Teach relaxation techniques (deep breathing, meditation)
- Encourage expression of concerns and fears
- Provide evidence-based information about labor and delivery
- For fatigue:
- Schedule short rest periods throughout the day
- Prioritize activities and delegate when possible
- Maintain regular physical activity for energy
- Ensure adequate nutrition
- For memory changes:
- Use reminder apps, lists, and calendars
- Keep important items in designated places
- Break tasks into smaller steps
- Reassure that changes are normal and temporary
Warning Signs to Report
Educate patients to report:
- Severe headache, especially if accompanied by visual changes
- Persistent depressed mood or thoughts of self-harm
- Extreme anxiety that interferes with daily functioning
- Seizures or loss of consciousness
- New onset of neurological symptoms (numbness, weakness, slurred speech)
Nursing Assessment in Third Trimester
Comprehensive nursing assessment during the third trimester is essential for identifying potential complications and providing appropriate education. The following table outlines key assessment parameters:
| Assessment Area | Parameters to Evaluate | Frequency |
|---|---|---|
| Vital Signs |
|
Every prenatal visit |
| Weight |
|
Every prenatal visit |
| Edema |
|
Every prenatal visit |
| Uterine Assessment |
|
Every prenatal visit |
| Fetal Well-being |
|
Every prenatal visit; daily fetal kick counts at home |
| Laboratory Tests |
|
As scheduled or indicated |
| Psychological Status |
|
Every prenatal visit |
| Signs of Labor |
|
Every visit after 36 weeks |
Assessment Best Practices
- Document all findings thoroughly in the patient’s record
- Compare current findings with previous assessments to identify trends
- Use standardized assessment tools when applicable
- Incorporate patient’s subjective reports of symptoms along with objective findings
- Ensure privacy and comfort during physical assessments
- Explain all assessment procedures before performing them
- Use open-ended questions to encourage patients to share concerns
Best Practices for Patient Education
Effective patient education during the third trimester is essential for promoting maternal comfort, ensuring compliance with care recommendations, and preparing for labor, delivery, and the postpartum period. The following evidence-based practices enhance the effectiveness of third trimester education:
Practice #1: Individualized Education
Tailor education to the individual’s learning style, literacy level, cultural background, and specific needs.
- Assess learning style (visual, auditory, kinesthetic)
- Adjust language complexity as needed
- Consider cultural beliefs about pregnancy and childbirth
- Incorporate patient’s specific concerns into education plan
- Use teach-back method to verify understanding
Practice #2: Multimodal Teaching Approaches
Utilize various educational methods to enhance comprehension and retention of information.
- Combine verbal instruction with written materials
- Use visual aids (diagrams, videos, apps)
- Provide hands-on demonstrations when appropriate
- Suggest reliable online resources and mobile applications
- Recommend group classes to supplement individual education
Practice #3: Staged Information Delivery
Present information progressively over time to prevent overwhelming patients and improve retention.
- Prioritize information based on immediacy of need
- Break complex topics into smaller, manageable segments
- Build on previously covered information
- Schedule follow-up discussions to reinforce key points
- Provide resources patients can review at their own pace
Essential Third Trimester Education Topics
Immediate Concerns
- Management of common third trimester discomforts
- Warning signs requiring immediate medical attention
- Fetal movement monitoring
- Nutrition and hydration needs
- Safe physical activity guidelines
- Sleep positioning and strategies
Preparation for Birth
- Signs of true vs. false labor
- When to call provider/go to hospital
- Birth plan development
- Pain management options during labor
- Breathing and relaxation techniques
- Hospital packing list
Postpartum Preparation
- Breastfeeding basics
- Newborn care fundamentals
- Postpartum recovery expectations
- Baby supplies and home preparation
- Postpartum mood disorders awareness
- Support system planning
Administrative Preparation
- Insurance coverage and billing information
- Family medical leave options
- Pediatrician selection
- Birth certificate and social security procedures
- Childcare planning (if applicable)
- Follow-up appointment scheduling
New Nursing Updates for Third Trimester Care (2023-2024)
Update #1: Enhanced Fetal Movement Monitoring
Recent research has reinforced the importance of daily fetal movement monitoring as a key indicator of fetal well-being.
- Current recommendations emphasize individualized baseline awareness rather than counting specific number of kicks
- Patients should be educated to recognize their baby’s normal movement patterns
- Any significant decrease in movement warrants immediate medical evaluation
- Mobile applications for tracking fetal movement can improve compliance and documentation
- Encourage daily monitoring sessions during times when the baby is typically active
Update #2: Mental Health Screening Integration
Increased emphasis on mental health screening and support during the third trimester to improve maternal-infant outcomes.
- The American College of Obstetricians and Gynecologists now recommends screening for anxiety in addition to depression
- Implementation of validated screening tools at 32-36 weeks to identify at-risk patients
- Development of clear referral pathways for mental health support
- Increased focus on trauma-informed care approaches
- Recognition of sleep disturbance as both a symptom and contributor to mental health concerns
Update #3: Virtual Prenatal Education
Following the COVID-19 pandemic, virtual options for prenatal education have been refined and validated as effective alternatives to traditional in-person classes.
- Hybrid models combining digital resources with in-person care show high patient satisfaction
- Virtual childbirth education classes with evidence-based curriculum
- Telehealth consultations for low-risk third trimester visits when appropriate
- Digital platforms for monitoring blood pressure, weight, and other parameters between visits
- Online communities providing peer support under professional guidance
Emerging Research Focus Areas
- Sleep quality interventions: Growing evidence links third trimester sleep quality with labor outcomes and postpartum recovery
- Microbiome considerations: Emerging research on maternal microbiome influences on neonatal gut health
- Postpartum preparation: Enhanced focus on preparing for the “fourth trimester” during third trimester education
- Partner inclusion: Structured approaches to meaningfully involve partners in third trimester preparation and education
- Culturally responsive care: Development of culturally tailored approaches to third trimester education
References
- Openstax. (2024). Care in the Third Trimester of Pregnancy. In Maternal-Newborn Nursing. https://openstax.org/books/maternal-newborn-nursing/pages/11-4-care-in-the-third-trimester-of-pregnancy
- Johns Hopkins Medicine. (n.d.). The Third Trimester. https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-third-trimester
- Mayo Clinic. (2025, February 7). 3rd trimester pregnancy: What to expect. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/pregnancy/art-20046767
- Soma-Pillay, P., Catherine, N. P., Tolppanen, H., Mebazaa, A., Tolppanen, H., & Mebazaa, A. (2016). Physiological changes in pregnancy. Cardiovascular Journal of Africa, 27(2), 89-94. https://pmc.ncbi.nlm.nih.gov/articles/PMC4928162/
- All4Birth. (n.d.). Understanding the Physiological Changes of the Third Trimester. https://www.all4birth.com/third-trimester-physiological-changes/
- UNICEF Parenting. (n.d.). Your third trimester guide. https://www.unicef.org/parenting/pregnancy-milestones/third-trimester
- Northwestern Medicine. (n.d.). Staying Comfortable in the Third Trimester. https://www.nm.org/healthbeat/healthy-tips/staying-comfortable-in-the-third-trimester
- Banjer, A. H., & Al-Hamdan, N. (2023). Physiology, Maternal Changes. In StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK539766/
- Bonilla, F., Chaudhary, A., Aurioles, G., & Kilpatrick, S. J. (2024). Antepartum Care in the Second and Third Trimester. In StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK448166/
- Conway Medical Center. (2024, July 10). The Third Trimester: Guiding Your Last Months of Pregnancy. https://www.conwaymedicalcenter.com/news/topic/the-third-trimester/