Baby’s Growth & Size

• Weight: About 3–3.5 pounds (1.4–1.6 kg).

• Length: Around 16 inches (40–41 cm) from head to heel.

• Baby is gaining about ½ pound (225 g) per week, mostly fat and muscle.

Development & Features

• Brain: Rapid development continues—the surface is becoming more wrinkled (with folds called sulci and gyri) to increase surface area for thinking and learning.

• Lungs: Still developing, producing more surfactant to help with breathing after birth, but not fully mature yet.

• Skin: Becoming smoother as fat builds up underneath; baby is starting to look plumper and less wrinkly.

• Bones: Fully formed, but still soft and pliable. Skull bones remain unfused for flexibility during delivery.

• Muscles: Strengthening—movements are more coordinated and powerful.

• Eyes: Baby can respond to light, open and close their eyes, and even start practicing blinking.

Movements

• You’ll feel a lot of rolling, stretching, and kicking—movements are strong, though space is getting tighter.

• Baby is also practicing grasping, sucking, and even hiccupping.

Vernix & Lanugo

• Vernix caseosa (the creamy coating) is thickening, protecting baby’s skin.

• Lanugo (fine hair) may start to shed but is still present.

Position

• Some babies may begin moving into a head-down position, but many still change positions frequently at this stage.

Immune System

• Antibodies are being passed from you to your baby through the placenta, helping to build their immune defenses.