Twins Development 3rd Trimester Highlights

Over the past three months of your third semester, your twins have gained fat, muscle tone, and mature lungs and are ready to be born! They're ready to kick, to cry, to smile, and to grasp your finger in their tiny fists! At the end of this trimester, your twins have:

  • Muscle tone from moving all about
  • Eyelids that open -- complete with eyelashes
  • Toenails
  • Sweet smiles
  • The ability to kick, grasp, and stretch
  • Eyes that open and close and respond to changes in light
  • Possibly, full heads of hair
  • Fully formed hearts, brains, and nearly all other organs and body systems
  • Testes that have descended into a baby boy's scrotum
  • Fingernails that reach to the end of the babies' fingers
  • About 16% body fat
  • Smooth skin and chubby legs
  • Bones and muscles ready for the outside world
  • Lungs ready to breathe and cry
WebMD Medical Reference Reviewed by Nivin Todd, MD on January 16, 2019



ACOG: "Your Pregnancy and Childbirth."

Moore: "The Developing Human."

Phillips, J. Pathology, October 2009.

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