Your developing baby – week 25

by Kaiser Permanente |
Fetus at week 25, illustration

Your baby continues to grow quickly. They're over 13 inches long now and weigh up to 2 pounds. At week 25 your baby is about the size of a papaya.

  • Lungs are fully formed but not yet ready to function outside the uterus.
  • Loud sounds can make your fetus respond with a startled movement and pull in their arms and legs.
  • Eyelids can open and close. 
  • Lungs continue to make surfactant, a substance needed for breathing after birth.
  • Nervous system continues developing.
  • Skin begins to look smoother as more fat is added. 

What else is going on?  Your baby can now move their tongue in and out of the mouth. Their nostrils are opening up, and more healthy fat is layering their body. In addition, small blood vessels called capillaries are forming just beneath the skin and filling with blood, providing important oxygen and nutrients to the skin’s cells. 

Your baby’s hearing and sense of touch continue to develop and improve. It’s not too early to sing lullabies.

This article has been created by a national group of Kaiser Permanente ob-gyns, certified nurse-midwives, pediatricians, lactation consultants and other specialists who came together to provide you with the best pregnancy, birth, postpartum, and newborn information.

Some of the content is used and adapted with permission of The Permanente Medical Group.