4 Weeks After Conception
No longer a flat disk, the sides of the embryo begin to fold along the long axis (a.k.a. the primitive groove or streak) and is three dimensional. The chest and stomach are forming, and the heart -- right now just a little tube -- starts beating around the 22nd to 25th day after conception. That wee heartbeat will be visible via ultrasound soon! Similarly, your baby's brain waves can now be measured with an electroencephalogram.
Here's a closer look at what your baby may look like right around four weeks after conception, or at six weeks menstrual age.

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See some ultrasounds from week six of pregnancy: |
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| Read a few articles about what you might expect during your first trimester: See them here |
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| Check out what some real moms had to say about their first trimester: Click to take a peek |
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Like this picture or this page? Click here to send this page to a friend! |
See other weeks here:
Note: These images and information are not meant to convey precise detail, but rather the general shape and progression of your baby as he or she develops. These drawings are not to scale, and are for educational purposes only. Every baby is different, and this information should not be construed as medical diagnosis or advice.
For more on your baby's development and changes in your body, be sure to check out our day-by-day pregnancy calendar!
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