In weeks 1 and 2 of pregnancy — the week of and immediately following your last menstrual period — your body is working hard to gear up for ovulation that will pave the way for baby around week 3 (so no baby quite yet). Conception occurs about two weeks from the first day of your last period, and that's when you're truly considered to be pregnant. When conception takes place, a zygote is created that is the basis for a new human being. What begins as an anxious egg waiting to be fertilized will develop into a super tiny embryo, or baby. The countdown to delivery day begins during the period right before fertilization, even though your egg and his sperm have yet to cross paths.

By weeks 4 and 5, the ball of cells in your fertilized eggs splits into two groups. Half of what's now called the embryo will become your sweet little one, while the other half forms the placenta — your baby's lifeline for food and oxygen. The embryo now has three distinct layers of cells from which your baby's internal organs and skin will develop. Baby weighs less than 0.04 oz.

Your baby's bones start to form at week 7, but they are soft for now. Baby is curled up in a C shape so it may be hard to detect some of what's going on, but the arm and leg buds that formed last week are taking on the shape of paddles. Also forming this week are your baby's mouth and tongue. The kidneys are in place now, too, and will soon begin their important task of waste management. The brain is growing and the face continues to form, including eyelids (that are still shut), though the eyes won’t develop until much later. Baby is about 1/2 inch in length and weighs less than an aspirin.

Congratulations! Your baby has graduated from the size of a blueberry to that of a raspberry and everything that is present in an adult human is present in the developing embryo. Baby is 1/2 to 3/4 inch long now, and growing at an amazing rate. All major organs and body systems are developing, and there are little swells where the eyes and ears will be. Tiny webbed fingers and toes are forming on what once looked like paddles for hands and feet. Baby's heart is beating at the incredible rate of about 150 to 170 times per minute — roughly twice as fast as yours. And even though you can't yet feel it, your baby's tiny trunk and limbs are moving. Hang in there, you only have 7 months to go.

Get excited! Your baby has moved from being an embryo to a fetus. The digestive tract and reproductive organs have formed, but it's still a little too early for even the trained eye to tell whether you're having a boy or a girl — although baby's heartbeat may be heard on ultrasound. Elbows, fingers and toes can be seen, and buds that will become teeth are appearing. Less than an inch long from head to rump, your curled-up little one is about the size of a cherry and weighs around .07 oz.

Your baby is really beginning to look like a little human now, and growing fast and furious. Bones and cartilage are forming and small indentations on the legs are developing into knees and ankles. The arms have elbows that can flex already, as well. Webbing is disappearing from between fingers and toes, and tiny nails are forming. So are your baby's choppers, even though they'll stay under the gums for another couple of months. Baby's head is rounder with more facial features, like lips and eyebrows. Baby weighs about .14 oz. and is over an inch long.

By week 11, your baby is distinctly human. Hands and feet are in front of the body, ears are nearly in their final shape, bones are hardening and baby even has a tongue. Your baby’s head is about half the size of the body. You still can't tell what baby's sex will be but ovaries are developing if it's a girl. Baby's body is straightening and the torso is lengthening. Your baby now measures anywhere from 1 1/2 to 2 inches long, just about the size of a small lime.

This is an exciting week! You may be able to determine if your baby is a boy or girl on an ultrasound, so be sure to tell your provider if you don’t want to know. Your baby is moving around, but you may not feel the movement, especially if this is your first pregnancy. Little hands are developing quickly and can now form a fist. A fine layer of hair covers much of baby's body. Most of your baby's systems and organs are fully formed — although there's still plenty of maturing for them to do. Since you're probably barely showing as of yet, it may be hard to believe that your baby has more than doubled in size during the past three weeks. Baby weighs about half an ounce and measures about 2.5 inches long. Only six months to go!

Congrats on entering the 2nd trimester! Did you know that your fetus is starting to make urine to create amniotic fluid? This becomes a cycle. Your fetus swallows amniotic fluid, which contains nutrients and antibodies, makes urine and releases it back into the amniotic sac. You might be able to see baby's breathing and swallowing movements on an ultrasound. At 13 weeks, tiny bones are beginning to form in the arms and legs. Baby will soon be able to get a thumb into his/her mouth. Also developing are the vocal cords, although you won't be able to hear any baby sounds just yet. Baby's length may be approaching 3 inches and weight around an ounce.

Your baby is growing by leaps and bounds, and doing some leaping as well. On the move almost constantly now, baby can put those tiny hands to the mouth with fluid motions. Eyes start to move, and the nose and taste buds are developing. A downy coating of hair called lanugo covers the body to provide warmth. Some babies — especially those born early — still have a fuzzy coating at delivery, but it disappears soon afterward. At about 3.5 inches long, your little one weighs about an ounce and a half.

Get ready for a growth spurt and lots of activity! As baby practices some aerobics, you may begin to feel movements. You can thank baby's brain for this, as it now controls all of baby's muscles. This week, your baby is getting bigger overall, with bones getting stronger and more visible on an ultrasound, the kidneys fully functional and making urine, and the heart pumping blood. Baby is close to 4 inches long, and weighs in at close to two and a half ounces.

Only 5 months to go now! It's time to choose some lullabies to sing. Tiny bones in your baby's ears are in place, making it likely that they can hear your voice. Baby's eyes are working too, making small side-to-side movements and able to see light. The backbone and tiny muscles in baby's back are gaining strength, so your little one's head and neck can straighten now more than ever. Your baby is 5-6 inches long and weighs close to 6 ounces.

Baby is about the size of your palm now! Since practice makes perfect, your baby is sharpening his/her survival reflexes (like sucking and swallowing) in utero. Body fat is accumulating, and a waxy substance called vernix is beginning to cover the thin skin to protect it in the womb. Fat gives your baby energy and will help provide warmth once baby is born. You may or may not feel it, but baby is hiccuping now too.

Your baby's nervous system is maturing rapidly, and unique fingerprints that have formed. Your baby goes to sleep and wakes up throughout the day. Thus why the art of yawning is being mastered. Loud noises or sudden movements can now stir your little one. Nerves in the brain are further developing into the ones that serve the senses of touch, taste, smell, sight and hearing. Baby weighs around 6 ounces now.

Your baby is getting stronger with each passing week! If you think you felt some "hello" jabs before, you will really notice them now. (First-time moms might not feel anything for a few more weeks, though.) Baby's legs are now longer than his/her arms, and that little body may stretch beyond 6 inches long this week. Your baby is now secreting enough vernix to protect the entire body, and is practicing lots of sucking — an essential skill for feeding down the road. Baby is getting heavier, too, at over a half pound in weight.

Your little champ weighs in near 1 pound and has a height, crown to rump, of about 6½ to 8 inches. In baby terms, you have a real heavyweight in your belly at week 20. If you're carrying a girl, your baby's uterus is fully formed this week and the vaginal canal is starting its development with primitive eggs forming in the ovaries. If it's a boy, the testes are beginning to descend. Either way, your baby may be sprouting a head of hair (but nothing that will need a cut anytime soon). You’re halfway through your pregnancy — hang in there!

It may be hard to imagine a whole carrot living in your belly, but that's what's going on right now. Your baby has no body fat at this point, but will steadily gain weight, weighing twice as much by week 25. There's still plenty of space for your little action figure to twist, turn and even do an occasional somersault. Baby's skin now responds to touch. So if you put pressure on your belly, your little one might move away or push back. The brain is also developing rapidly. Baby's fingers and toes are fully formed, including tiny finger prints and toe prints. The liver and pancreas are working hard to develop completely too. Baby has reached about 10 to 11 inches in length and weighs about near 1¼ pound.

A papaya and a bag of sugar. Both can describe your little one this week in terms of size and weight, respectively. Baby's sense of touch and sight are really being fine-tuned now. In fact, your little one's grip is quite strong, strong enough to hold on tight to that umbilical cord. Don't worry, though — it's tough enough to handle it. Your baby can perceive light and dark much better than before, even with those fused eyelids. Lungs are developing rapidly, and they will begin making a protein called surfactant to help promote independent breathing once baby leaves the womb. Your sweetie can also hear your voice, your heartbeat, your gurgling stomach and the whoosh of blood circulating through your body.

If you talk to your baby, you may feel her move as she begins to really recognize your voice this week! During sleep, your little one goes into REM (rapid eye movement), and tear ducts are starting to form. Baby has almost grown to a foot in length now, and is beginning to gain some serious weight. Baby may be nearing one and a half pounds.

Baby's beautiful little face is almost fully formed now, complete with eyelashes, eyebrows and hair. Nostrils are opening for "practice breathing" as well. Your baby’s lungs are well-developed, though it’s still too early for independent breathing. Much of baby's serious weight gain comes from growing organs, bones, muscle and accumulating baby fat.Your baby is over a foot long now, and weighs anywhere from 1½ to 2 pounds.

Your baby is growing fast, especially the nervous system: brain, spinal cord and nerves. The nervous system is an important one that helps your baby move, think and feel. That wrinkled little skin is starting to smooth out as your baby adds more fat this week, too, while stretching to more than 13 inches long. The skin is changing in another way as well. It's getting more pink because small blood vessels, called capillaries, are forming under the skin and filling with blood. (That's a good thing.)

Baby now weighs nearly 2 pounds and measures 14-plus inches long. Your little one will soon be feeling rather cramped in your uterus — but for now there's still plenty of space in there to grow. Baby’s eyes, which have been closed for the past few months so that the retina (the part of the eye that allows images to come into focus) could develop, are fully formed and starting to open and closet. The nervous system is kick-starting some of the body systems, too. It’s beginning to control breathing movements and body temperature. Brain activity is up, meaning your baby can respond to things like noises with an increase in pulse rate or movement. Melanin is being made by baby's body now to protect that fragile skin from the sun after birth and contribute to skin color.

Small movements have become big! Your baby is now kicking and stretching in the womb, a lot. The lungs and nervous system continue to develop, including the rapidly growing brain. At this point, baby may recognize your voice and that of your partner. Hearing is really progressing as the network of nerves to the ears matures — though the sounds heard in the womb are muffled thanks to the coating of vernix covering baby. You'll be feeling the extra weight these days, with your baby coming in close to 2 pounds and more than 14 inches long.

Welcome to your third trimester! Your little work-in-progress may start settling into the proper position for birth (ideally, head facing downward toward your body's nearest exit). Baby now weighs about 2¼ pounds and is almost 15 inches long when measured head to toe, about the size of a large eggplant. Eyes are open wide now, with baby being able to blink and sense changes in light. These are just a few of the impressive skills in the works. Others include coughing, more intense sucking and better breathing.

What your baby doesn't put on in length right now, he will gain in weight! In these last 10 weeks of pregnancy, babies put on half their total body weight so it's important to eat healthy foods to give baby the nutrients he needs to keep growing. Added fat will make the skin less wrinkly and baby's little body fill out. Baby weighs close to 3 pounds and measures 15 1/2 to 16 inches long. He's getting pretty close to his birth length.

Your baby’s lanugo, the soft fine hair that covers the body, is beginning to disappear while hair on baby's head continues to grow. The head will remain soft and flexible for birth, while the other bones begin to harden. Until now, the surface of baby's brain was smooth — but it begins to take on grooves and indentations to allow for an increased amount of brain tissue, and lots of smarts. Baby is a hefty 3 pounds now and sitting tight at about 16 inches long.

That little coconut in your belly will gain about a half pound each week from here on out, and weighs in around 3½ or 4 pounds now. Baby is sleeping more, which is why you may be noticing fewer periods of movement. Your baby’s brain is working overtime, and the different regions are beginning to form. In fact, the brain can now control baby's body heat. It's also getting good at processing information, tracking light and perceiving signals from all five senses.

Wow, baby's having another growth spurt! Your sweetie is anywhere from 17 to 18 inches long and may tip the scales close to 4½ or 5 pounds. With all the fat that’s accumulated, your baby’s skin is no longer translucent. And, taste buds have really developed. When baby swallows amniotic fluid, he/she gets a sample of the foods you're eating and may acquire a preference for them. Baby's digestive system is ready to go in anticipation of moving to mouth feeding.

Chubby baby features are on the way! Your baby is steadily gaining weight and will eventually take on that cherub look everyone loves. With that much baby inside your belly, your amniotic fluid level has maxed out at 33 weeks pregnant, making it likely you have more baby than fluid now. That's one reason why some of the pokes and kicks feel pretty intense these days. Plus, baby's pushing 17+ inches long, so there is plenty of "leg" with which to jab. Another important milestone is being reached about now: Your baby's own immune system is in place and antibodies are being passed from you to your little one to build up defenses. Here's to a healthy little one.

If it hasn't already happened, your baby may be on the move — getting ready for the big day by (typically) flipping around to a head-down position. Baby's head can turn and that little body can now go from side to side. Tiny fingernails and toenails have probably reached the tips of the digits in preparation for that first postpartum manicure. This week, your baby is approaching 5¼ pounds and a whopping 18 inches long.

Your baby's once skinny arms and legs are now quite plump, and irresistibly soft. Standing tall now, your little one is at a full 18 inches or more and may pack on anywhere from 1 pound to several up until delivery day. At about this time, your baby will begin to “drop”, or move lower, toward your pelvis. But the brain and lungs are still developing, so your little one isn’t quite ready to debut yet. A baby's brain at 35 weeks weighs only two-thirds of what it will weigh at 39 to 40 weeks. The part that surrounds that amazing brain — the skull — remains soft, and for good reason. A soft skull will allow your baby to squeeze more easily through the birth canal in a few weeks. Hang in there!

It's getting too crowded in the womb for your baby to give you a good hard kick anymore, but you should still feel movement. If you notice drastic changes in baby's activity level, call your healthcare provider. The reason for the lack of space is your baby now weighs about 6 to 7 pounds and is likely over 18 inches long. Just one month to go!

You’re getting close, but you (and baby) are not quite there yet! Your baby’s brain, liver and other major organs still have some developing to do. That tiny head is still growing, too, and will be roughly the same circumference as the chest at birth. Fat continues to accumulate with the purpose of keeping baby warm in the world. Your little superstar is also passing the time by rehearsing for that big debut, practicing breathing by inhaling and exhaling amniotic fluid, thumb sucking, blinking and pivoting from side to side. Baby is a lengthy 19 inches this week.

At 38 weeks, baby is considered full-term and is ready to make its appearance at any time. Your little one isn't quite so little anymore, weighing about 7 pounds and measuring 19 inches in length, give or take an inch or two. Thanks to baby still putting on weight, you’re probably feeling pretty uncomfortable. It won't be for much longer, though!

Since you're now carrying a full-term baby, his/her weight is around 7 to 8 pounds and length is 19 to 21 inches. Those measurements won't change much going forward to delivery day. At this point, baby has shed most of the white creamy substance called vernix and the fine coat of lanugo that has covered the skin for months. Make sure your hospital bag is packed and your birthing plan is ready.

By the time baby arrives, you will have a little one the size of a watermelon to hold. That could feel like close to 9 or 10 pounds. Everything is now fully developed and ready to function independent of you. Remember, your due date is just an estimate so don't worry if your baby decides to stick around beyond 40 weeks — just keep in close contact with your healthcare provider. Many first babies are late, and that little cutie will be so worth the wait!