What is the size of my baby during the 1st trimester?

These are the stages of a child's growth during the first trimester, starting at Week 3:

  • Week 3 - Your baby is a microscopic cluster of cells. This is the stage during which the sperm and egg unite to form a zygote, or a tiny one-celled structure. As the zygote moves, the cells divide very quickly and form a blastocyst, or cluster of hundreds of cells.
  • Week 4 - The embryo is only about 1/2 to 1 mm long! It already has two layers—the epiblast and the hypoblast—that will eventually develop into organs.
  • Week 5 - The embryo already has three layers: the ectoderm, mesoderm, and ectoderm. It’s only about 1 to 3 mm long!
  • Week 6 - Your baby's heart is beating and its facial features are forming. Your baby is about a quarter inch long.
  • Week 7 - Your baby's facial features are becoming more defined, and little paddle-like hands are developing. Your baby is about a half an inch long, or the size of a blueberry.
  • Week 8 - Your baby is starting to move! (You can’t really feel it yet, though.) Your baby is a little over half an inch long, or the size of a lima bean.
  • Week 9 - Your baby has developed many of its physical characteristics and looks like a human. Your baby is around an inch long, which is the size of an olive or grape.
  • Week 10 - Your baby is officially considered a fetus. It's a little over an inch long.
  • Week 11 - Your baby is about one and one-half to two inches long, or about the size of a fig. Your baby's head makes up half of its entire length.
  • Week 12 - Your baby is around three inches long, or about the size of a large lime. Even though length is still the best way to determine the size, your baby weighs almost an ounce this week!

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.