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Q&A: Fetus in First Trimester?

What basic changes does my baby go through in the first trimester?
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Updated
February 28, 2017
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In the first trimester (through week 13), baby starts off as a tiny ball of cells called a blastocyst, becomes an embryo when the bundle implants into the wall of your uterus, and officially reaches fetus status after eight weeks. The placenta forms to keep baby connected to all those nutrients you’re trying to hold down, and baby starts growing into a, well, baby. In these few weeks, her major organs, nervous system, head, face, ears, arms, fingers, legs and toes form — maybe before you even start to show! Bones, lungs and hair also start to grow while  temporary teeth buds develop and baby’s heart begins beating.

_American College of Obstetrics and Gynecologists. Your pregnancy and birth. 4th ed. Washington, DC: ACOG; 2005. _

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.

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