Twins Development 2nd Trimester Highlights

By now, you may know the sex of your babies. They already have eyebrows. Even more exciting, your twins can recognize your voice! At the end of this trimester, your twins have:

  • Fully formed organs that continue to grow.
  • Hard skeletons.
  • Hearts beating 100 pints of blood a day.
  • Ears that can hear sounds and know your voice.
  • Genitalia that can be seen and the sex determined.
  • Fully formed lungs not yet ready to breathe in air.
  • Early development of bronchioles, the airways of the lungs. Differentiation is still taking place.
  • Vernix, a waxy, waterproof material that covers and protects the babies' skin.
  • Fully formed hands and feet that are often put in the babies' mouths.
  • Brown fat, which helps produce heat to keep your babies warm.
  • Hair and eyebrows on the babies' heads.
  • Soft, downy hair called lanugo that covers the babies' bodies to provide warmth.
  • Ovaries in girl babies.
  • Testes are still in a baby boy's abdomen.
  • Fully formed fingers and toes with fingerprints.
  • Very active brains -- even in sleep.
  • Cute chubby cheeks.

WebMD Medical Reference Reviewed by Nivin Todd, MD on July 25, 2014



ACOG: "Your Pregnancy and Childbirth."

Moore: "The Developing Human."

Phillips, J. Pathology, October 2009.

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