Pregnancy and Fetal Development

Picture of First Trimester (12 Weeks)

Picture of First Trimester (12 Weeks)
First Trimester: The Baby at 12 Weeks
  • The nerves and muscles begin to work together. Your baby can make a fist.
  • The external sex organs show if your baby is a boy or girl. A woman who has an ultrasound in the second trimester or later might be able to find out the baby's sex.
  • Eyelids close to protect the developing eyes. They will not open again until the 28th week.
  • Head growth has slowed, and your baby is much longer. Now, at about 3 inches long, your baby weighs almost an ounce.
Reviewed by William C. Shiel Jr., MD, FACP, FACR on August 21, 2009

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Text: - Healthy Pregnancy: Stages of Pregnancy