Your Developing Baby: Week 12

What's going on with your baby in pregnancy week 12? Find out all about important pregnancy milestones and exciting fetal development specific to this week of pregnancy!

Week 12 American Institute of Ultrasound in Medicine -

Now that your baby-to-be is fully formed, all of her various organs and structures are gaining definition and growth. For example, her kidneys are beginning to function this week, Nutrients are provided by the placenta and delivered through your baby's umbilical cord. Her little body also gets rid of liquid waste through the umbilical cord. Later, some of Baby-to-be's urine might also be secreted into the amniotic fluid surrounding her, but this is normal and doesn't harm the baby.

Baby's various body systems are also beginning to work, although at a very basic level. Her nervous system is establishing connections between the brain and the developing baby's muscles. Along with jerky motions of her legs and arms, she might try more complex movements, such as squinting her eyes, moving her delicate fingers or toes, even sucking her thumb. Her reproductive system is also continuing to develop, but your sonographer would be hard-pressed to find and identify the gender with an ultrasound.

With all of her systems becoming stronger and more developed, you might be able to hear your baby-to-be's heartbeat during your normal prenatal office visit. Your health care provider will use a special instrument, called a Doppler, to pick up baby's heartbeat by passing the device over your abdomen.

    Terms to Know

    BPD (biparietal diameter): A measurement of the fetus' head. Used to determine the width of the head, the sonographer will measure from just above one ear to the other.

    Important Information About Your Pregnancy

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    Images courtesy of the American Institute of Ultrasound in Medicine (


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