You're three weeks into the third trimester, and things are moving quickly. Your baby is growing faster than at any other point in pregnancy, gaining roughly 200 grams per week from here on out. The bones are hardening — a process called ossification that requires significant calcium from your diet. And the movements you're feeling are increasingly powerful, because your baby now has real muscle mass behind those kicks and stretches.
Track your progress with our Due Date Calculator.
Your Baby This Week
Size: Butternut squash — about 38.6 cm (head to toe)
Weight: About 1.15 kilograms
Your baby is well over a kilogram and growing rapidly. Key developments this week:
- Bones are hardening rapidly. The skeleton, which was mostly cartilage earlier in pregnancy, is calcifying throughout the body. This requires a substantial and continuous supply of calcium. The skull bones are an exception: they remain softer and more flexible to allow for passage through the birth canal and to accommodate rapid brain growth after birth.
- Muscles are growing stronger. Those kicks you've been feeling are becoming genuinely forceful. You may see the movement from the outside now — a foot or elbow pressing against the belly wall.
- Brain development is intensive. The third trimester is a critical window for brain development. The cerebral cortex, which governs thought, sensation, movement, and language, is developing its characteristic folded structure. This folding process — called gyrification — dramatically increases the surface area available for neural connections.
- Red blood cell production. The bone marrow is fully responsible for producing red blood cells now, and production is high to support both the growing baby and the oxygen demands of the developing brain.
- Fat accumulation accelerates. White adipose tissue is filling in under the skin, giving your baby more of the rounded, smooth appearance of a newborn and helping to regulate temperature after birth.
- Adrenal glands are producing hormones. The fetal adrenal glands are proportionally large at this stage and are producing significant amounts of cortisol and DHEA, which contribute to lung maturation and other aspects of preparation for birth.
Your Body This Week
Third trimester is in full swing, and your body is responding:
- Pelvic pressure. As the baby grows and potentially begins to shift into a head-down position, you may feel increased pressure in the pelvis, groin, and inner thighs. This can make walking uncomfortable.
- Hemorrhoids and constipation. Pregnancy hormones slow the digestive system, and the growing uterus puts pressure on the rectum. Increasing fiber intake (fruits, vegetables, whole grains), drinking plenty of water, and gentle movement are the most effective preventive strategies.
- Varicose veins. Increased blood volume and pressure continue to affect the veins in the legs. Compression stockings, elevation when resting, and avoiding long periods of standing or sitting can help.
- Rib pain. The baby is using your ribcage as a footrest. Sitting up tall and practicing gentle stretches can provide temporary relief.
- Increased fetal movement. The WHO and ACOG note that healthy babies move throughout the third trimester, and you should feel movement every day. Do your kick count daily.
- Prenatal appointments. You're likely seeing your provider every two to three weeks now. These appointments include blood pressure checks (to monitor for preeclampsia), urine tests, fundal height measurements, and fetal heartbeat monitoring.
Tips for Week 29
1. Calcium-rich foods every day. Your baby is pulling calcium directly from your reserves if your diet doesn't provide enough — this contributes to bone density loss for you. Recommended intake is 1,000 mg per day during pregnancy. Dairy, fortified plant milks, sardines, almonds, and leafy greens are all strong sources.
2. Sleep on your left side. It improves blood flow to the uterus, kidneys, and the baby by relieving pressure on the inferior vena cava (the large vein returning blood from the lower body to the heart). If you wake up on your back, just roll back to your side — don't stress about it.
3. Prepare for the glucose test follow-up if needed. If you were diagnosed with gestational diabetes, ensure you're following your management plan. Blood sugar control in the third trimester is critical for preventing complications including macrosomia, preterm birth, and neonatal hypoglycemia.
4. Research newborn care. Bathing, feeding, cord care, safe sleep — these all feel urgent and intimidating before they feel routine. Starting now, with books, videos, or a dedicated newborn care class, means you'll approach birth with more confidence.
5. Take care of your mental health. Third-trimester anxiety is extremely common, particularly around birth, postpartum change, and parenting. If anxious thoughts are disrupting your sleep or daily function, speak to your provider. Perinatal mental health support is widely available and genuinely effective.
When to Call Your Doctor
- Decreased or absent fetal movement. You should feel your baby move every day. If you can't count 10 movements in 2 hours at a time your baby is normally active, call your provider.
- Signs of preeclampsia: severe headache, blurred vision or visual disturbances, sudden swelling in the face or hands, upper abdominal pain on the right side — these are medical urgencies requiring same-day evaluation
- Preterm labor signs: contractions before 37 weeks that are regular and increasing in intensity, pelvic pressure, lower back pain that comes and goes rhythmically, or significant change in vaginal discharge
- Severe or sudden leg swelling on one side — can indicate DVT (deep vein thrombosis), more common in pregnancy
- Fever, severe abdominal pain, or signs of infection
Related Tools & Articles
- Due Date Calculator — Calculate your estimated due date
- Contraction Timer — get familiar before you need it
- Hospital Bag Checklist — pack it this week
- Pregnancy Week-by-Week Overview — full timeline
- Milestone Tracker — track your baby's development