Parenting timeline.

the action or process of fertilizing an egg, involving the fusion of male and female gametes to form a baby

This week you ovulated and now the moment you’ve been waiting for has finally arrived: You’ve conceived and your soon-to-be-baby has started on its miraculous transformation from single cell to baby boy or girl! Once the winning sperm makes its way through the egg's outer layer, the now single-cell fertilized egg — or zygote — immediately forms a barrier to prevent other sperm from penetrating (sorry guys, too late). But your zygote doesn't stay single for long: within days it divides into two c

Your baby has found its home: The blastocyst that will develop into your baby has completed its six-day journey from your fallopian tube to your uterus. Once there, it burrows into your uterine lining and implants — making that unbreakable connection to you that'll last the next eight months (and a lifetime after that). As soon as that little ball of cells is settled in its new home, it will undergo the great divide — splitting into two groups. Half (now called the embryo) will become your son o

It takes a lot of developing to become a baby — all the major (and minor) bodily systems (digestive, circulatory, nervous and so on) and organs (heart, lungs, stomach…you get the idea) have to form from scratch. One of the first systems to be operational is the circulatory (or blood) system — along with its companion organ: the heart, which you may even be able to see it beating on an early ultrasound. When you’re 5 weeks pregnant, your baby's heart is made up of two tiny channels called heart t

You might be coping with full-blown pregnancy symptoms (sorry), but there's plenty of good news too. The folds of tissue in the prominent bump on top (the head) are developing into your baby's jaw, cheeks and chin — what will eventually become one adorable face. And are those little indentations on both sides of the head the adorable dimples you always hoped your baby would inherit from your mom's side of the family? No, they're ear canals in the making. Small bumps on the face will form the eye

Your baby's approximately a quarter of an inch in length now — about the size of a blueberry. Sounds pretty tiny still? Consider this for a little perspective: Your baby is 10,000 times bigger now than it was at conception a month ago. At 7 weeks pregnant, most of that growth is concentrated in the head (the better to store all those smarts) as new brain cells are generated at the rate of 100 per minute. How's that for a budding genius?

Your baby is growing at an amazing rate — about a millimeter every day. How's your baby measuring up this week? At a length of about half an inch right now, your baby has graduated from blueberry-sized to raspberry-sized. But baby’s size each week is getting a bit hard to estimate and here's why: Growth occurs at about the rate of one millimeter each day, but that growth isn't necessarily just in height. Spurts can occur in the arms, legs, back and other parts of your baby's body. That means big

Would you believe your baby is having his or her first graduation already? Yes, it's true: At 9 weeks pregnant, your scholar-to-be has ended his or her embryonic stage and is entering the fetal period now (good-bye embryo, hello fetus). Your fetus is now about one inch long, the size of a medium green olive (but no martinis, please). The head has straightened out and is more fully developed, the ears are much more prominent and some new organs (the liver, spleen and gallbladder) are forming. You

Your baby's growth is fast and furious when you are 10 weeks pregnant. He or she is nearly an inch and a half long and the size of a prune, but not nearly as shriveled (even with all the time spent in water). In fact, your baby is really taking a human shape now. Bones and cartilage are forming and small indentations on the legs are developing into knees and ankles. The arms (complete with elbows) can flex already (how is that for magical?), but don't run to the store for a baseball bat just yet

Slightly more than two inches long now and weighing about a third of an ounce, your baby has been pretty busy growing this week. While you can't tell this baby's gender by its cover yet, testes are developing if it's a boy and ovaries if it's a girl. And by week 11 of pregnancy, baby has distinct human characteristics: hands and feet in front of her body, ears nearly in their final shape, open nasal passages on the tip of her tiny nose, a tongue and palate in the mouth and visible nipples. Her h

By now your baby weighs a full half-ounce, with a crown-to-rump length of about two and a half inches — about the size of a large plum. It's hard to believe (especially from the outside, since you're probably barely showing at this point), but your baby has more than doubled in size during the past three weeks.

What's up with your baby? Well, besides being as large as a peach now, that big old noggin of hers is now about half the size of her crown-to-rump length (that’s one reason why your little peach looks more like an alien from outer space at this point). By the time you give birth, her body will catch up, measuring three-quarters of her total size. But don't compare your fetus with the fetus next door. Starting about now, babies begin growing at different paces, some faster than others, some more

Growing by leaps and bounds, your baby is leaping and bounding. Now the size of your clenched fist, your baby is on the move almost constantly — and those movements are a far cry from those jerky twitches of last trimester (though you won't feel any of them for weeks to come). They are now ballet-like, smooth and fluid. Speaking of ballet, it'll be years before you'll start nagging your offspring to stand up straight — but unbelievably, he or she is doing it right now, without any prodding! No s

Curious why your body is finally looking pregnant? It's because at 15 weeks pregnant your baby is quickly growing bigger each week — he or she is as long as four and a half inches right now. Need a better visual (and a snack)? Hold a large navel orange in your hand — that's how big your little darlin' is. (Now that you're done looking, peel that orange and eat it for a delicious two servings of vitamin C!). And with each passing week, your fetus is also looking more and more like the baby you're

Your baby now weighs in at a whopping three to five ounces and he's four to five inches in length. The backbone and tiny muscles in his back are gaining strength, so he can straighten out his head and neck even more. And thanks to his developing facial muscles, your baby is capable of making a few expressive frowns and squints, even at this early stage. His eyes are finally working too, making small side-to-side movements and perceiving light (although the eyelids are still sealed). Peekaboo!

My how your baby has grown! Your little one weighs about three and a half ounces and is about the size of your palm (or about five inches long). Body fat (baby's, that is) is beginning to form and will continue to accumulate through the end of your pregnancy (join the club, baby!), so that by the time you give birth it will make up about two-thirds of his or her weight. Baby’s heart is now regulated by the brain (no more random beats) to beat 140 to 150 times per minute — about twice as fast as

At five and a half inches long (remember, that's crown to rump) and five ounces in weight, (about the size of that boneless chicken breast you're making for dinner), your baby may be large enough now (or anytime in the next few weeks) for you to feel him twisting, rolling, kicking and punching his way around the womb. And now for the skill of the week: The art of the yawn has been mastered by your baby (you may feel those soon, too!). In fact, you might catch a glimpse of that adorable yawn and

Six inches long this week and about a half pound in weight, your baby has gone through a little growth spurt and is the size of a large mango. Your little action figure is able to choreograph Matrix-like moves at 19 weeks pregnant. Arms and legs are finally in proportion, neurons are now connected between the brain and muscles and cartilage throughout the body is turning to bone. All these upgrades combine to give your baby more control over limb movements. Which explains all that kicking, stret

You've got a heavyweight in your belly at 20 weeks pregnant (well, in baby terms, anyway). Your little champ weighs about 10 ounces and has a height, crown to rump, of about six and a half inches. Think small cantaloupe (and probably as sweet too). While your baby is definitely getting bigger, there's still plenty of growing room in there, which allows him to twist and turn (and allows you to feel his acrobatics!).

How big is your baby? About the size of a large banana (seven inches in length and almost 11 ounces in weight). Your developing baby still has a great deal of room in your womb — though like anyone who lives in one space for a long time, this tenant will soon begin to feel cramped. Until those uterine walls start closing in, however, there's plenty of space for twisting, turning and even an occasional somersault (so that's what you were feeling last night!). With all that belly dancing going on,

Guess what? At 22 weeks pregnant, your baby (who’s about the size of a small doll) has finally broken the one-pound mark. How heavy is that? Hold a one-pound box of sugar in your hand the next time you're in the grocery story (and expect people to ask you why you're grinning from ear to ear). Is the box eight inches long? That's about the length your baby is too! Your little doll’s eyelashes and eyebrows are also well formed now — and even more hair is sprouting atop that cute little head. You'd

At eight inches and slightly over a pound, this week marks the beginning of some serious weight gain. Your baby should double his weight over the next four weeks alone (and you may feel as though you do, too). His skin is a bit saggy since it grows a lot faster than fat — but soon he’ll start to fit his frame as fat deposits fill things out. By the time your baby is born, he or she will be pleasantly plump and filled out, from chubby cheeks to chubby toes. And although at 23 weeks pregnant your

Your baby is about eight-and-a-half inches long (standard letter size!) and weighs one-and-a-half pounds, gaining steadily at a rate of about six ounces per week. Much of that weight comes from growing organs, bones, muscle and accumulating baby fat. Wondering what (and who) your baby will look like? If you had a baby cam at 24 weeks pregnant, you'd almost be able to tell by now. That beautiful face (though still tiny) is almost fully formed, complete with eyelashes, eyebrows and hair. Is your b

Your baby is growing by leaps and bounds, reaching nine inches in length and passing the pound and a half mark — taller than two juice boxes stacked one on top of the other and almost as heavy as four of them. What else is going on this week? Your baby's skin is turning pinker — not because he or she's getting overheated (in fact, the amniotic fluid is perfectly climate-controlled, keeping your baby at an always comfortable temperature), but because small blood vessels, called capillaries, are f

What's up with your baby? She now weighs a full two pounds and measures nine-plus inches. Your baby will soon be feeling a little cramped in your uterus — but not to worry, there's still plenty of room for your baby to grow. It just means your gymnast will have less room for those somersaults, cartwheels and other Olympic feats.

This week it's time to trade in the old crown-to-rump measurement for a new head-to-toe standard. By the end of the second trimester, your baby is now measuring nearly 14 inches — more than a foot long. His weight is creeping up the charts too, coming in at just over two pounds (double four weeks ago). Most babies this age, yours included, still like to snuggle in a slightly curled position inside the uterus (thus the term "fetal position").

Your baby is settling into the proper position for birth, with his head facing downward (toward your body's nearest exit!). Your little work in progress is now about 2.5 pounds and almost 16 inches long (measured head to toe). He's busy these days blinking (outside in the real world, blinking is necessary to help keep foreign objects out of the eyes). That skill is just one of an already impressive repertoire of tricks he's working on, like coughing, more intense sucking, hiccupping and, perhaps

At 29 weeks pregnant, your baby weighs nearly three pounds now and measures about 17 inches. Though she's getting pretty close to her birth length, she still has to chub out a bit. In fact, over the next 11 weeks, she'll more than double — or even come close to tripling — her weight. As more fat is deposited under the skin surface, her wrinkled skin is smoothing out. This fat, called white fat, is different from the earlier brown fat that your developing fetus accumulated. Brown fat is necessary

Your belly’s increasing size is a definite clue that your baby is getting bigger every day — now he’s weighing in at over three pounds (he’ll be packing on the weight at a rate of half a pound per week for the next seven weeks).

Weighing in at three-plus pounds and measuring 18 inches long, your baby is quickly approaching his birth length — though he's got to pack on another three to five pounds before D-day. He's also putting in longer stretches of sleep, which is why you're probably noticing more defined patterns of wakefulness (and movement) and rest (when he’s pretty still).

What's up with your baby? She's starting to get ready for her big debut, tipping the scales at almost four pounds and topping out at just about 19 inches. In these past few weeks, it's all about practice, practice, practice as she hones the skills she'll need to thrive outside the womb — from swallowing and breathing to kicking and sucking. In anticipation of that momentous transition to mouth feeding, your baby's digestive system is all set and ready to go. And though you’re weeks away from D-d

This week your baby may be anywhere between 17 to 19 inches in length and could grow up to another full inch this week — especially if he or she has been on the shorter side. She weighs more than four and a half pounds and is still gaining weight (about half a pound a week — weight gain can range from a third more to a full doubling before the big debut). With that much baby inside your uterus, your amniotic-fluid level has maxed out at 33 weeks pregnant, making it likely you have more baby than

This week your baby is clocking in at five pounds and could be as tall as 20 inches. Need a visual? Hold a five-pound bag of flour in your arms and imagine it's your soon-to-be-born baby (cradle it and you'll only get strange looks in the baking aisle). Then stack three such bags one on top of the other (and get ready for some more strange looks, maybe from the same clerks who saw you grinning and holding that one-pound box of sugar a few weeks ago). That's how tall your baby is at 34 weeks preg

Your baby is standing tall (so to speak) this week at about 20 inches (baby's pretty much reached the in utero limit). But at about five and a half pounds, she is continuing her steady weight gain: She’ll pack on anywhere from one pound to several, including large amounts of baby fat, up 'til delivery day. In fact, back in the middle of your pregnancy your baby's weight was only two percent fat; now at 35 weeks pregnant, that percentage has soared to closer to 15 percent...and will increase to 3

Forget your aching back (and everything else!) by trying to focus on your baby, who is now about six pounds and 20 inches long. Growth will experience a slowdown now, both so your baby will be able to fit the narrow passageway to the outside and also so he or she can store up all the energy needed for delivery.

Congratulations! At 37 weeks pregnant, you've got what is officially considered a full-term baby, even with three weeks to go. That means if your baby was to leave the wet nest this week, he or she would likely thrive. But it doesn't mean he's finished growing — in fact, he's still packing on about a half an ounce per day or half a pound a week. At this age, the average fetus weighs about 6.5 pounds — boys, though, are likely to be heavier at birth than girls. And here's a bit of boy baby trivia