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Pregnancy & Baby Development: Weeks 9-13

Weeks 9 to 13 of your pregnancy brings your first trimester to a close, and you can finally see your baby bump. If you're wondering what's going on in there, you should know that your developing baby has been very busy. It's amazing that in just over three months he'll have gone from a single cell to a fully-formed—albeit very small—fetus.

Week 9

Just nine weeks into your pregnancy, seven weeks after conception, your embryo is about 3/4 of an inch long. Those little toes that you can't wait to kiss are just starting to form, notes the Mayo Clinic. Your developing baby's arms are growing and beginning to bend at the elbows. He's developing eyelids and ears at this point. The reproductive organs are also beginning to form, but it will still be a couple of months before you'll be able to see the baby's gender.

Week 10

By the 10th week of pregnancy, the embryo's tail disappears. Your developing human is barely the size of a peanut, but all of his vital organs are formed. His fingers and toes may begin to separate. Inside of him a lot of changes are happening. Those organs are beginning to function in unison. If it's a boy, he'll be producing testosterone. Little tooth buds—the ones that will no doubt cause a few cranky nights in the future—are beginning to form.

RELATED: 10 Things You Don't Know About Infants

Week 11

Congratulations—your baby has graduated from embryo to fetus. His face, limbs and organs are formed, his fingers and toes have lost their webbing and look like yours, only much smaller. He's nearly doubled in size since week 9, but he's still barely bigger than a paperclip, at just over an inch long. Soon, your fetus will be closing his eyes, and according to MedlinePlus, they won't be opening again until you're about 28 weeks along.

Week 12

Your fetus has grown another inch in just a week, and he's big enough now that you might begin feeling the first flutters of movement around your pubic bone or at the top of your uterus. If you don’t feel him yet, don’t get discouraged—you will soon enough. His face is looking more and more human by the day as his nose and jaw become more distinct. The inside of his mouth is forming into a palate. He's growing nails as well.

Week 13

You're at the home stretch of the first trimester now. You may or may not be able to feel her yet, but know that she's wiggling around right now, testing those new limbs. You have a well-developed placenta at this point, and your fetus is getting the nutrients and oxygen she needs. By 13 weeks, your developing baby may begin putting her thumb into her mouth—she can't fully suck yet, as those muscles haven't finished developing, but that won't stop her from trying.​

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