Fetal Development

Fetal Development answers your questions about the changes that take place in the womb during pregnancy. Learn about each of the three trimesters and the developmental milestones that occur in each.


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Guide to Being 20 Weeks Pregnant

You're about to enter your third trimester of pregnancy, and with all the changes happening in your life and your body, you might feel overwhelmed. Take a moment to relax while reading our guide to being 20 weeks pregnant.

Guide to Being 24 Weeks Pregnant

By the time you hit 24 weeks, the novelty might be wearing off. Still, you're nearing the home stretch, and believe it or not, this may be the most comfortable you feel until after your love bug arrives. So what do you need to know?

Guide to Being 25 Weeks Pregnant

Hello, 25 weeks! You're halfway through month six, and your baby's body is taking leaps and bounds toward the first breath, the first cry and the first grip on your finger. Motherhood is close. But what comes first?

Guide to Being 16 Weeks Pregnant

This is a big week for baby mamas! You might find out your little one's gender, and you can also start feeling your baby's movements. Also, it's time to book that babymoon you've been dreaming about -- you deserve it.

Guide to Being 17 Weeks Pregnant

Pregnancy is a strange and wonderful time at 17 weeks along. Sure, your gums are bleeding and you're dizzy all the time, but you've got life growing inside you! Find out what your little guy or gal is up to.

Guide to Being 18 Weeks Pregnant

There are no breaks in the action when you're pregnant. It's week after week of miracles and heartburn. Week 18 is no exception. What's going on inside you?

Guide to Being 19 Weeks Pregnant

By 19 weeks, you're probably starting to truly feel pregnant. It'll get worse before it gets better, but don't worry: As soon as you feel those tiny kicks, you'll forget it all.

Guide to Being 14 Weeks Pregnant

Now solidly in your second trimester, you're probably more excited than ever about your little bun in the oven. At 14 weeks, development is progressing at a breakneck pace. What's next?

Guide to Being 15 Weeks Pregnant

You're rounding third on month four, and with just 25 waist-expanding weeks until the moment you've been waiting for, you might be feeling better than you have in some time. What should you expect in week 15?

Guide to Being 12 Weeks Pregnant

The day comes when you take a drive without a pit stop and get through a day without getting sick. Hopefully first-trimester symptoms are starting to ease up in week 12, leaving plenty of room for a new set of sensory experiences.

Guide to Being 13 Weeks Pregnant

In week 13, pregnancy is probably starting to be a whole lot more fun. Lots of women find the middle months to be the easiest, with fewer unpleasant symptoms and new reasons to be excited. So what should you expect in this banner week of pregnancy?

Guide to Being 10 Weeks Pregnant

By Week 10, if you were to look closely at your baby, you'd notice she doesn't look like a tadpole anymore. Her embryonic tail, at the bottom of the spinal cord, has disappeared and her rapidly developing spinal nerves have become visible. What else can you see?

Guide to Being 11 Weeks Pregnant

Hopefully your morning sickness has started to subside and your energy level has increased. You might even be starting to see that "pregnancy glow." But you will be experiencing some new changes ahead. Let's take a look.

Guide to Being Seven Weeks Pregnant

By now, your baby is transforming from a featureless, c-shaped tube into a tiny creature with a head. What else can you expect during your seventh week of pregnancy?

Guide to Being Eight Weeks Pregnant

While you won't be feeling it yet, your baby is actually starting to move around. What else can you expect from your eighth week of pregnancy?

Guide to Being Four Weeks Pregnant

You're having the symptoms -- morning sickness, bloating, missed period -- but you aren't sure if you're really pregnant. Four weeks is about the right time to take the pregnancy test and get an accurate diagnosis. Why? Read on to find out.

Guide to Being Nine Weeks Pregnant

You're two-thirds of the way through your first trimester and really starting to feel -- if not actually look -- pregnant. At this point, you may also be experiencing some unpleasant side effects. But what exactly is going on during week nine?

Guide to Being Five Weeks Pregnant

In week five, your fetus is about the size of a sesame seed! You're popping folic acid and trying to fight off morning sickness. Here's what you and your partner should know about this early stage of prengnancy.

Guide to Being Six Weeks Pregnant

During week six of your pregnancy, those cravings and bouts of morning sickness are in full swing! The good news? You might be able to hear your baby's heartbeat. What else can you expect when your little one is a half-inch long?

Guide to Being Two Weeks Pregnant

Like "one-week pregnant," two weeks along exists only in retrospect. That doesn't mean the second week of pregnancy doesn't matter, though. There's no baby yet, but there's a lot of preparation going on.

Guide to Being Three Weeks Pregnant

If you're trying for a baby, this is your big moment. Conception typically occurs during week three, which means you are not just technically pregnant, you're actually pregnant. At last, a microscopic ball of cells to call your own.

Guide to Being One Week Pregnant

When you're looking down the long road to motherhood, week 40 can look more appealing than week one. It can seem a long time to wait to feel that tiny fist wrapped around your finger. So what is week one really like, and how exactly can you tell you're one week along?

Alertness in the Womb

From early on in your pregnancy, your baby is more like a newborn than you might think. Find out how he sleeps, moves around, listens to sounds and has thoughts and memories while still in the womb.

Pregnancy Pictures

Explore the stages of pregnancy with these pictures and get a first-hand look at developing fetuses and ultrasound technology. Do you know what fundal height is or when the limbs are developed? Take a look and find out.

How A Fetus Grows

The journey of the fetus through pregnancy is a complex and fascinating miracle that scientists have broken into three phases -- the three trimesters that represent a nine-month pregnancy. Learn how a fetus grows