Key Fetal Development Milestones During Pregnancy

by Gabriel Humffray

Fetal DevelopmentCongratulations, you're pregnant!

Wondering what's happening in your womb?

For starters, your baby grows in leaps and bounds during these months. Fetal development follows a predictable schedule.

Here are the fetal development milestones you can expect as the weeks roll by.


Conception typically occurs around two weeks into your pregnancy. Wait a minute! What happened to those first two weeks?

During those first two weeks, you're not actually pregnant. Your body gets a spot ready for the baby by growing a layer of rich tissue for nourishment.

Once you've "furnished the womb," the egg and sperm meet up in a fallopian tube and form a single cell called a zygote. After conception, the egg makes its way to the uterus, divides to form a cluster of cells, burrows into the womb lining and begins its rapid growth.

Embryonic Development

During this critical stage of growth, your baby's development is in full swing. It's going to be a busy few weeks! The baby's brain, spinal cord, heart and other organs begin to form.

• At four weeks pregnant, the cells divide into a group that will make up the placenta and one that will make up the baby.

• By six weeks pregnant, the baby's heartbeat begins and arms and legs develop. Basic facial feature become apparent and your baby takes on a "C" shape.

• At eight weeks pregnant, the intestines begin forming and teeth start to grow in the gums. If you saw your baby now, you'd note the beginning of tiny nostrils, shell-shaped ears, visible eyes and legs and arms.

• By 11 weeks pregnant, the end of the embryonic stages, your baby's brain and major organs are well started. Even the eyes and joints are forming. The head still makes up about half of the baby's length, but the body will soon work at catching up, developing rapidly in the next weeks.

Fetal Development

Your precious babe has a new name -- fetus. That's a step up in the world from embryo! Development takes on a whole new meaning now. Soon you'll be able to find out your baby's gender and feel tiny kicks and punches.

• Between weeks 11 and 16, your tiny miracle works at developing distinguishable genitals, hair, nails and vocal cords (surely you'll appreciate this accomplishment in a couple years). The liver and kidneys begin to function.

• Weeks 16 to 20 signal another growth spurt. Your baby's laying down a bit of fat beneath the skin. That minuscule heart pumps an amazing 25 quarts of blood every day. Meconium starts accumulating in the bowels. You might have notice hiccups. Babies get them now.

• During weeks 21 to 24, development seems to slow down but things are still happening. The eyelids and eyebrows are formed and if your baby is a boy, his testes begin to decent from the pelvis.

• Weeks 25 to 28 mark a period of carrying on and wrapping up loose ends. During this time, the baby's lungs secrete surfactant as the body prepares to breathe air. On other fronts, retinas form and the eyes open. If born at 28 weeks, 90 percent of babies survive.

• From weeks 29 to 40, your baby focuses on lung development. Most of the major organ systems are complete. The baby adds fat, lays in immunities and continue fine-tuning that brain until birth. Thirty-seven weeks pregnant is considered full term, but studies indicate that your baby does better if born after 39 weeks pregnant.

Watch videos of your growing baby right now in our video library!


Kier's picture

Submitted by Kier on

I love reading what happens at each stage of pregnancy I'm at. It really helps me think about, and connect, with my baby Smile

Military Mom's picture

It's definately a good overview from the very beginning...and answers the question of why include those 2 weeks that you arent actually pregnant Wink