Pregnancy Week 13

You're entering your second trimester this week! Learn what is happening with your baby's development and how to read food labels to make smart nutritional choices.

Week by week baby size image. Week by week baby size image.

How big is baby?

Your beautiful baby is the size of a Meyer lemon this week—and his vocal cords are beginning to develop.

Baby's Length: 2.91in.
Baby's Weight: 0.81oz.
Fetus at Week 13 What the baby looks like at week 13 of fetal development. Med ART Studios Explore More

Baby's Development

Your baby is constantly getting bigger and cuter, and his face is looking more human-like every day. His ears have moved up from his neck into place and his eyes -- which are looking more and more like your baby blues (or browns, or greens) -- have moved from the sides of the head to the front of the face. Up until now, his head has been outpacing his body, but now his body is growing faster. His legs still need to grow longer, but this week his arms will lengthen to be proportionate with his body, and he'll be able to stick his thumb in his mouth. Also by now, all of your baby's essential organs and systems have formed.

Baby Week 13

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Tiny vocal cords are developing. However, sounds will not be produced for approximately 7 more months.This week marks another developmental milestone as you enter the second trimester. The developing fetus is now almost 3 inches long.The pancreas begins to produce insulin, and the intestines move from inside the umbilical cord to their permanent home in the abdomen.
Week by week baby ultrasound image. Week by week baby ultrasound image. American Institute of Ultrasound in Medicine - AIUM.org

Week 13 Ultrasound

In this profile shot, notice that the baby-to-be is lying with her bottom on the left-hand side of the image and her head to the right. (Even though the fetus is referred to as "she" here, the sonographer may or may not be able to identify the baby's gender at this point.) Her legs are clearly visible raised up, knees bent. The line across the middle of the profile is the sonographer's measurement of baby's crown-rump length (CRL). With this measurement, the sonographer is able to determine your baby's age. 

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Watch Baby's Growth

Second Trimester Begins: Weeks 13 to 17 of Pregnancy

Mom's changing body

From tripping to dropping dishes, you might be feeling clumsier these days. Relaxin, another hormone that messes with you during pregnancy, loosens up your ligaments and joints in preparation for birth. Even though you need the extra give only in your pelvis, the hormone works on your entire body, which means your hands and feet are affected, too.

Weekly Tip

Don't forget to keep up with your regular dental checkups. According to the Mayo Clinic, about 80 percent of expectant mamas suffer from gum softening or bleeding.

Pregnancy Confidential Podcast

Who Says We Can't Eat for Two?

It's Week 13 and, for many of you, the fog of the first trimester is finally lifting: You're probably starting to feel like your old self again, minus the constant nausea and irksome food aversions. But out with the old and in with the new: With the start of the second trimester often comes extreme hunger. It sometimes feels like your body is making up for everything it missed out on in the last three months and wants to eat everything in its path (minus those food aversions—those tend to stick around). Good thing you're eating for two... But are you? It seems science always wants to burst your happy bubble.

This Week's To-Do List

This Week's FAQs

    Must-Reads

    A Week of Delicious Pregnancy Meals and Snacks

    Eating healthy when you're pregnant can be hard: You have crazy cravings and an even crazier schedule. But eating right is important for your growing baby, so check out these nutritious, dietician-approved meals. There's even fro-yo!

    Second Trimester Begins: Weeks 13 to 17 of Pregnancy

    Here's to hoping you're no longer feeling nauseated or exhausted! Right now your baby's brain and eyes are making dramatic strides each day. Learn all about it.

    The Inside Story: Your Baby in Week Thirteen

    As you enter your second trimester, your baby is growing quickly--and you will be able to hear his heartbeat at your next doctor's visit!

    Your Developing Baby: Week 13

    What's going on with your baby in pregnancy week 13? Find out all about important pregnancy milestones and exciting fetal development specific to this week of pregnancy!

    Comfort Essentials During Pregnancy

    Treat your tired body to some refreshing goodies.

    Maternity Style Secrets

    Look your best during every trimester!