Fetal development week by week

Follow your baby’s development week by week, from conception to labor, in these amazingly detailed, doctor-reviewed images.

Now nestled in the nutrient-rich lining of your uterus is a microscopic ball of hundreds of rapidly multiplying cells that will develop into your baby. This ball, called a blastocyst, has begun to produce the pregnancy hormone hCG, which tells your ovaries to stop releasing eggs.

Your baby resembles a tadpole more than a human, but is growing fast. The circulatory system is beginning to form, and the tiny heart will start to beat this week. Your baby is the size of a sesame seed.

Your baby has doubled in size since last week, but still has a tail, which will soon disappear. Little hands and feet that look more like paddles are emerging from the developing arms and legs. Your baby is the size of a blueberry.

Your baby’s basic physiology is in place (she even has tiny earlobes), but there’s much more to come. Her embryonic tail has disappeared. She weighs just a fraction of an ounce but is about to start gaining weight fast. Your baby is the size of a grape.

Your baby is almost fully formed. She’s kicking, stretching, and even hiccupping as her diaphragm develops, although you can’t feel any activity yet. Your baby is the size of a fig.

This is the last week of your first trimester. Your baby’s tiny fingers now have fingerprints, and her veins and organs are clearly visible through her skin. If you’re having a girl, her ovaries contain more than 2 million eggs. your baby is the size of a pea pod.

Your baby’s brain impulses have begun to fire and he’s using his facial muscles. His kidneys are working now, too. If you have an ultrasound, you may even see him sucking his thumb. Your baby is the size of a lemon.

The patterning on your baby’s scalp has begun, though the hair isn’t visible yet. His legs are more developed – find out when you’re likely to feel your baby kick! His head is more upright, and his ears are close to their final position. Your baby is the size of an avocado.

Your baby is flexing his arms and legs, and you may be able to feel those movements. Internally, a protective coating of myelin is forming around his nerves. your baby is the size of a bell pepper.

Your baby can swallow now and his digestive system is producing meconium, the dark, sticky goo that he’ll pass in his first poop – either in his diaper or in the womb during delivery. Your baby is the size of a banana

Your baby now looks almost like a miniature newborn. Features such as lips and eyebrows are more distinct, but the pigment that will color his eyes isn’t present yet. Your baby is the size of a spaghetti squash.

Your baby cuts a pretty long and lean figure, but chubbier times are coming. His skin is still thin and translucent, but that will begin to change soon too. Your baby is the size of an ear of corn.

Your baby is now inhaling and exhaling amniotic fluid, which helps develop his lungs. These breathing movements are good practice for that first breath of air at birth. Your baby is the size of a bunch of scallions.

In this illustration, you’ll notice that your growing baby takes up quite a bit of room these days. In the third trimester, you might be peeing more often or have leg cramps as he presses on nerves in your hips and back.

Your baby’s muscles and lungs are busy getting ready to function in the outside world, and his head is growing to make room for his developing brain. Your baby is the size of a butternut squash.

Your baby can now turn his head from side to side. A protective layer of fat is accumulating under his skin, filling out his arms and legs. Your baby is the size of a coconut.

The bones in your baby’s skull aren’t fused yet. That allows them to shift as his head squeezes through the birth canal. They won’t fully fuse until adulthood. Your baby is the size of a pineapple.

It’s getting snug inside your womb! Your baby’s kidneys are fully developed, and his liver can process some waste products. Your baby is the size of a honeydew melon.

Your due date is very close, but though your baby looks like a newborn, he isn’t quite ready for the outside world. Over the next two weeks, his lungs and brain will fully mature. Your baby is the size of a bunch of Swiss chard.

At 39 weeks, your baby will be considered full-term. In the illustration, you can see the mucus plug sealing your uterus and how squished your intestines are now.

If you’re past your due date you may not be as late as you think, especially if you calculated it solely based on the day of your last period. Sometimes women ovulate later than expected. Your baby is the size of a small pumpkin.