Third Trimester (Weeks 28–40): Preparing for the Grand Entrance

Tracking your baby’s progress during this trimester is like watching a masterpiece unfold rapid development, weight gain, and final touches to essential skills.

• Week 28: Your baby’s eyelids can open and close; the central nervous system starts controlling temperature and breathing movements. Expected size: ~10 inches crown-to-rump, around 2¼ lb (1,000 g)
• Week 29: Kicks, stretches, and first grasping movements become more purposeful
• Week 30: Hair grows thick, and the bone marrow takes over red blood cell production; length ~10½ inches, weight ~3 lb (1,300 g)
• Week 31: Major structural development is complete, and a burst of rapid weight gain begins
• Week 32: Lanugo (fine hair) begins shedding; baby may stretch hands and legs. Measurement: ~11 inches, ~3¾ lb (1,700 g)
• Week 33: Eyes react to light; bones harden while the skull remains flexible for birth
• Week 34: Fingernails reach the fingertips; baby ~12 inches, ~4½ lb (2,100 g)
• Week 35: Skin smooths, and limbs become chubby as fat layers grow
• Week 36: Space tightens; baby often turns head-down in preparation for birth
• Week 37: Head may engage in the pelvis (“lightening”); grasp reflex strengthens. This marks early term
• Week 38: Toenails form; head and abdominal circumference become similar; weight: ~6½ lb (2,900 g)
• Week 39: Body fat increases to keep your baby warm after birth; full-term status achieved
• Week 40: Due date arrives! Estimated size: ~14 inches crown-to-rump (approx. 7½ lb / 3,400 g), although normal birth weights vary.