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.


Very little is known about what or how fetuses see. This study shows their vision capabilities are more advanced than previously thought.

A new device tested on fetal lambs could change care for human preemies, immersing them in a "biobag" with lab-made amniotic fluid, keeping them underwater for weeks.

New analysis also shows that preemies born between 22 and 24 weeks of pregnancy are less likely to develop health issues.

To make sure your little bundle of joy arrives healthy, it's a good plan to have regular monitoring tests during your pregnancy. See what's in store for the next nine months.

Thirty-nine weeks down, only one or two more to go! Here's what's going on with you and baby during these final days of pregnancy.

You're having a baby any day now! We'll take you through the final preparation for the long-awaited event.

At 41 weeks pregnant, it's very possible your due date has come and gone. Read on for why your little bundle of joy could just not be ready to make an appearance.

So, your due date came and went, and you're still lugging around that passenger. How can someone so little be so stubborn?

Well, it's official: You're overdue, post-term, post-date or just plain sick of this miracle happening inside you. So what's taking that (not so) little one so long?

That baby is technically ready to go, and it could happen any minute now. So what are you experiencing at 37 weeks, and what's happening in that enormous belly of yours?

You've got two short, waddling weeks left, give or take, before your baby greets the world, and the excitement (and anxiety) might be keeping you up at night. So what are you experiencing in week 38?

Though you're only six weeks from your official due date, you might feel like you're looking at the longest six weeks of your life. What can you expect in week 34 of your pregnancy?

At 35 weeks pregnant, you're well into the homestretch. Your baby is basically done growing, so all you have to do now is relax until he makes his arrival.

In your 36th week of pregnancy, it's easy to appreciate why gravid is another word for pregnant. See what you can look forward to as you gear up for the big day.

You're in the third trimester now, and your baby bump has swollen to a baby boulder! If you haven't decorated your nursery or picked out a baby name, it's time to get cracking. We've got a few more hints for moms at 28 weeks.

While you might be experiencing less-than-pleasant things such as constipation and swelling in your hands and feet, take a look at the exciting developments happening with your baby during your 29th week of pregnancy.

Welcome to the big 3-0 -- your 30th week of pregnancy, that is. You've got about 10 weeks to go until your baby arrives, so let's take a look at what's happening during the homestretch of your pregnancy.

Fasten your seatbelts, ladies: While you may carry to 42 weeks (or, Lord help you, beyond), "full term" is just six weeks off. That means in a month and a half, you've got the green light to give birth to that tiny person you're carrying around.

Feel like you just might burst? Hang in there: At week 32, you've got as little as five weeks until you're full-term, and just eight until you enter "overdue." You're nearing the end. And the beginning. And that baby is huge.

What's the mind-body experience you'll have at 33 weeks? Every kick helps you count down to the day you'll deliver your little acrobat. The nursery's ready, but there are still some things to think about and some important preparations to make.

At 21 weeks pregnant, your little bundle of joy will arrive in just a few more months! Here's a guide to what's happening in your body right now.

The second half of your second trimester can sometimes feel like the middle of a long road trip. What pleasant surprises does week 22 hold in store? Read on to find out.

Here are some of the things you might be feeling, thinking about and wishing your partner knew as you head into week 23 of your pregnancy. And yes, the skin on your belly actually will stretch a little more.

By week 26, your discomfort, anxiety and excitement are probably growing at similar rates. Baby is roughly, astonishingly, just 14 weeks off. So what should you prepare for now?

If, up to now, you've barely been showing, week 27 could be your entry into the "obviously pregnant" zone. You're getting so close -- what should you expect during this transition between the second and third trimesters?