Week 12 of Pregnancy: What's Going On Inside

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By week 12, you can now hear your baby's heartbeat with a Doppler heart monitor.

Wondering what your baby looks like at 12 weeks? Your baby is now about the size of a lime. Average baby length is 2.4 in. (61 mm).

How your baby is changing

Here are some important changes that happen around this time.

  • By 10 weeks of pregnancy, embryos have nearly all of the body structures that adults have. Their brain is now more complex. After this point, we call this a fetus.
  • During this month, the fetus's limbs, hands, and head start to move. Eyelids cover their eyes, and their fingernails are starting to grow.
  • At the end of this month, fetuses start a big weight gain.


Current as of: November 9, 2022

Author: Healthwise Staff
Medical Review:
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
William Gilbert MD - Maternal and Fetal Medicine

The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.