At 39 weeks pregnant, your baby is considered full term and is preparing for birth.

Here’s what’s happening with development at this stage:

Baby’s Growth & Size

• Weight: Around 7 to 8 pounds (3.2-3.6 kg) on average, the size of a Mini Watermelon!

• Length: About 19-21 inches (48-53 cm) from head to heel.

• Every baby is different, so yours may be a little smaller or larger and still completely healthy.

Development & Features

• Organs are mature: The lungs are fully developed and producing surfactant, which keeps the air sacs open once breathing begins.

• Brain development: The brain is still rapidly developing, making important connections, which continues after birth.

• Fat stores: Your baby has built up enough fat to regulate body temperature outside the womb.

• Skin: No longer wrinkly or translucent; now smoother, with a healthy layer of fat.

• Hair & nails: Many babies have a full head of hair and fingernails that may extend past the fingertips.

• Movements: Space is tight, so you may feel more rolling and stretching than sharp kicks, but activity should still be regular.

Position

• Most babies are now in a head-down position, with the head engaged in the pelvis, ready for birth.

Immune System

• Baby is receiving important antibodies from you through the placenta, which help protect against infections after birth.

What This Means for You

• Your baby could arrive any day now—some come right at 39 weeks, others at 40 or even 41.

• Full-term babies born at 39 weeks typically breathe well on their own, can regulate body temperature, and are ready to feed.