Dr. Barra OBriain, MD,Local Family Physician Vancouver

The Third Trimester of Pregnancy

Maternal Physical & Mental Changes

  • Physical Discomforts: Back pain, pelvic pressure, heartburn, shortness of breath, frequent urination, and difficulty sleeping due to bump size.

  • Braxton Hicks Contractions: Irregular, painless “practice” contractions that help tone the uterus.

  • Emotional Shifts: Increased anxiety or restlessness regarding delivery, energy bursts aimed at preparing the home (“nesting”), and physical fatigue.

Fetal Development Milestones

  • Weeks 28–32: The fetus opens its eyes, gains body fat, and develops rhythmic breathing movements. Bones are fully formed but remain soft.

  • Weeks 33–36: Brain and nervous system mature rapidly. The fetus typically moves into a head-down (vertex) position in preparation for birth.

  • Weeks 37–40: Reaching full term (week 39+). Lungs are mature, fine body hair (lanugo) sheds, and fat reserves peak to help regulate body temperature after birth.

Dr. Karen Nordahl, MD, Family Physican, Vancouver

Third Trimester Exercise

Exercise in the third trimester focuses on gentle mobility, stamina, and preparing your pelvic floor for labor. As your belly grows and your center of gravity shifts, workouts should shift toward low-impact movements that reduce pressure on your joints and lower back.

Common Emotional Drivers in Trimester 2

  • Anatomy Scan Stress: The 20-week ultrasound brings relief for many, but waiting for results or navigating unexpected findings can provoke intense anxiety.

  • Body Image & Identity Shifts: As your bump becomes visible, rapid weight gain and physical changes can trigger body dysmorphia, loss of bodily autonomy, or feelings of discomfort.

  • “Reality Setting In”: Feeling fetal movement (quickening) makes the pregnancy concrete, which can trigger stress around birth preparation, finances, parental readiness, and relationship dynamic changes.

  • Hormonal Stabilization (and Surges): While mood swings may feel less erratic than in the first trimester, sustained high estrogen and progesterone levels still impact brain chemistry.

RD Andy Desantis, Toronto, Ontario

Educational video describing Tree Nut Allergies

Managing Third-Trimester Eating Challenges

  • Heartburn & Acid Reflux: The growing uterus compresses the stomach, pushing gastric acid upward. Eat 5 to 6 small meals throughout the day instead of 3 large ones, and avoid lying down for 1 to 2 hours after eating.

  • Fullness & Bloating: High levels of progesterone slow down digestion. Eat slowly, chew thoroughly, and keep fiber intake consistent while drinking plenty of water.

  • Gestational Diabetes Management: If diagnosed, focus on complex carbohydrates with a low glycemic index (brown rice, quinoa, oats) paired with protein and healthy fats to maintain stable blood sugar levels.

In the third trimester, your baby undergoes rapid weight gain, bone mineralization, and brain development. Nutrition during these final months focuses on supplying enough energy, protein, and key minerals to support this surge in growth while preventing maternal deficiencies like anemia

Caloric & Hydration Needs

  • Calorie Increase: You need roughly 450 extra calories per day above your non-pregnant baseline (about 150 calories more than in the second trimester). Focus on nutrient-dense snacks like Greek yogurt with nuts, apples with peanut butter, or whole-grain toast with avocado.

  • Hydration: Aim for 8–10 cups (2 to 2.5 liters) of water daily. Proper hydration helps prevent constipation, hemorrhoids, urinary tract infections, and premature contractions caused by dehydration.