Your future baby is not even an embryo yet. With a new menstrual cycle beginning, your body is gearing up to ovulate again. Will that soon-to-be released egg and that determined sperm merge to become the beautiful baby you're expecting to expect? You won't find out until next month.
So why call these the first two weeks of pregnancy — when you're not even pregnant yet? Because it's hard to pinpoint the precise moment when sperm meets egg. Sperm from your partner can hang out in your body for several days before your egg comes out to greet it. Likewise, your egg can be kept waiting for a day or two for tardy sperm to make their appearance (sort of like being kept waiting for a date — huh?). In order to give all pregnancies some standard timing, your practitioner will date your 40-week pregnancy from the first day of your last menstrual period (which you're having right now — so mark the calendar). What this means is that you've already clocked in two weeks of pregnancy before you've even become pregnant! (How's that for getting a head start?)
In the meantime, while your uterus is awaiting its tenant, start acting like a good landlord. Consider these two weeks of waiting as a final walk-through before the baby takes over the keys. You may not be pregnant yet — at least technically — but it isn't too early to start acting like you are.
Learn more about being 1 & 2 weeks pregnant.
3 Weeks Pregnant
Your baby is a microscopic ball of cells this week, one-fifth the size of the period at the end of this sentence. But you've got yourself a baby-in-the-making, ready to begin the incredible journey that will end in your arms.
Three weeks into your pregnancy — and conception has finally occurred. The magic moment when sperm and egg fuse (otherwise known as fertilization) results in a zygote, a single-cell organism made up of genetic material from both you and your partner. Peel away that technical jargon and you've got yourself a baby-in-the-making, ready to begin the incredible journey that will end in your arms.
So congratulations are in order. Now, will this single cell miraculously transform into a girl or a boy? Though it will be months before you'll be able to find out for sure (if you choose to), that remarkable determination has already been made. Ready for a crash course in biology? The fertilized egg (aka your baby) contains 46 chromosomes — 23 from you, 23 from Dad. The mother (yes, that's you!) always provides an X chromosome. The father can provide an X or Y chromosome. If the sperm that fertilizes your egg carries an X chromosome, the XX zygote will be a girl. If the sperm is Y-bearing, then your XY zygote will be a boy.
The single cell doesn't stay single for long: Within hours, the cell divides, then each cell divides again. Within days, you're walking around with a microscopic ball of cells, one-fifth the size of the period at the end of this sentence. Tiny? Certainly. But don't underestimate its potential. In fact, your baby (now known as a blastocyst) is making its first solo trip — traveling this week from your fallopian tube to your uterus.
Learn more about being 3 weeks pregnant.
4 Weeks Pregnant
Your little ball of cells is splitting into two groups this week. One will become your son or daughter while the other becomes the placenta — the lifeline that channels nutrients to your baby and carries waste away.
Your baby has found its home — 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). Once firmly in place, the ball of cells undergoes the great divide — splitting into two groups. Half (now called the embryo) will become your son or daughter while the other half becomes the placenta — the lifeline that channels nutrients to your baby and carries waste away.
Despite its extremely tiny size — no longer than one millimeter and no bigger than a poppy seed (think about that as you eat your morning bagel) — your little embryo is busy setting up house. The amniotic sac that boards your baby (also called the bag of waters) is forming, as is the yolk sac (don't worry, you're not having a chicken), which will later be incorporated into your baby's developing digestive tract.
The embryo now has three distinct layers of cells that will grow into specialized parts of your baby's body. The inner layer, known as the endoderm, will develop into your baby's digestive system (with help from that yolk sac), liver, and lungs. The middle layer, called the mesoderm, will soon be your baby's heart, sex organs, bones, kidneys, and muscles. The outer layer, or ectoderm, will eventually form your baby's organs and tissues, including the nervous system, hair, skin, and eyes.
Learn more about being 4 weeks pregnant.
5 Weeks Pregnant
Your baby looks a lot like a tadpole this week, with a rudimentary head and a tail. But don't worry — there's no frog in your future. In fact, you're fewer than eight months away from holding a real prince (or princess) in your arms.
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. Right now, your baby's heart is made up of two tiny channels called heart tubes — and they're already hard at work, beating to their own drummer (it will be weeks before those beats become coordinated). When those tubes fuse together, your baby will have a fully functioning heart (though it almost certainly already has its grip on yours). Also in the works this week are several other organs, including the neural tube (the precursor to your baby's brain and spinal cord), which hasn't yet sealed, but by next week, that open-door policy is over.
Learn more about being 5 weeks pregnant.
6 Weeks Pregnant
Practitioners measure embryos as small as yours from precious little crown to cute little rump. That's because as your baby grows, his or her legs will be bent, making it hard to measure the full length of the body. This week your baby's crown-to-rump measurement is anywhere from a fifth to a quarter of an inch, and growing — making it the size of a sweet pea (your little sweet pea!).
So, if your womb had a view, what would you see? The folds of tissue in the prominent bump on top (the head) are developing into your baby's jaws, cheeks, and chin. 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 eyes and button nose in a few weeks time. Also taking shape this week: your baby's kidneys, liver, and lungs.
Learn more about being 6 weeks pregnant.
7 Weeks Pregnant
How does your baby grow? Pretty fast, actually. This week, your baby's length is approximately a quarter of an inch — 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.
The biggest growth this week is your baby's head (the better to store all those smarts in), with new brain cells being generated at the rate of 100 cells per minute. How's that for a budding genius?
And talking about buds, your baby is going out on a limb this week as his or her arm and leg buds begin to sprout and grow longer (and stronger), dividing into hand, arm, and shoulder segments — and leg, knee, and foot segments (though the limb buds look more like paddles than hands or feet at this early stage).
Also forming this week are your baby's mouth and tongue. And although your embryo is just one month old, it's already gone through three sets of kidneys. The ones in place now are the permanent set and are poised to begin their important work of waste management. In about a week, your baby will start producing urine. Lucky for you, there's no need for diapers (yet). As your baby matures inside you, much of that urine will be excreted into the amniotic fluid, swallowed again by your baby, and then excreted again in a continuous cycle.
Learn more about being 7 weeks pregnant.
8 Weeks Pregnant
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 weekly growth 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. So, big changes will be occurring every which way in the coming months.
What else is changing right now? A close-up view of your little embryo (say cheese!) would reveal a more baby-like appearance (and thankfully, a less reptilian one). You'd see an upper lip forming, the protruding tip of that cute button nose, and tiny (and very thin) eyelids. And check out those hands and feet! Your baby's webbed fingers and toes are differentiating now, so give your baby a round of applause.
All this growing is exciting for your baby too. How do you know? His or her heart is beating at the incredible rate of 150 times per minute. (That's twice as fast as your heart beats.) Your baby's digs are growing, too. Amniotic fluid increases at a rate of about two tablespoons per week to accommodate your womb's growing tenant.
Learn more about being 8 weeks pregnant.
9 Weeks Pregnant
Sunrise, sunset: Would you believe your baby is having his or her first graduation already? Yes, it's true: 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. Your fetus is also making spontaneous movements of his or her arms and legs now that minuscule muscles are beginning to develop, though you won't feel your tiny dancer for at least another two months.
While it's way too early to feel anything, it's not too early to hear something (possibly). Your baby's heart is developed enough — and grown large enough — so that its beats can be heard with a Doppler, a handheld ultrasound device that amplifies the lub-dub sound the heart makes. But don't worry if your practitioner can't pick up the sound of your baby's heartbeat yet. It just means your shy guy or gal is hiding in the corner of your uterus, or has his or her back facing out, making it hard for the Doppler to find its target. In a few weeks (or at your next visit) the miraculous sound of your baby's heartbeat is certain to be audible for your listening pleasure.
Learn more about being 9 weeks pregnant.
10 Weeks Pregnant
Your baby's growth is fast and furious now. 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 it spends 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, but don't run to the store for a baseball bat just yet. Though your baby's arms are taking shape and getting stronger, each one is only about the size of this number 1.
The tooth bud fairy is making her appearance this week, heralding the arrival of your baby's little choppers, which are forming under the gums. (Those pearly whites won't break through the gums until your baby is close to six months old). Other systems are go, too. Your baby's stomach is producing digestive juices, the kidneys are producing larger quantities of urine, and, if your baby's a boy, he's already producing testosterone (yikes!).
Learn more about being 10 weeks pregnant.
11 Weeks Pregnant
Slightly more than two inches long now and weighing about a third of an ounce, your fetus is growing by leaps and bounds. And so is his or her head, which is equal in length to the rest of the body (don't worry — all fetuses are top-heavy).
On the crown of that large head (and over the rest of the body), hair follicles are forming. Fingernail and toenail beds begin to develop this week and by next week, the nails themselves will start to grow (so don't forget to add a baby nail clipper to your to-buy list).
Your baby's body is straightening and his or her torso is lengthening (sounds like a yoga pose, doesn't it?). Other poses your baby can assume now: stretches, somersaults, and forward rolls. And 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.
Learn more about being 11 weeks pregnant.
12 Weeks Pregnant
This week marks a turning point for your baby. The herculean task of developing new bodily structures is nearing an end as most of your baby's systems are fully formed. Now comes the maintenance phase, during which the systems continue to mature for the next 28 weeks and the organs get to work.
Your little fetus weighs as much as half an ounce now, and the crown-to-rump length is about two and a half inches (the size of a large plum — busily working his or her way through the whole produce department). 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. And that's just on the outside — there's plenty going on inside too. The digestive system is beginning to flex its digestive muscle — literally — as it starts practicing contraction movements, a skill your baby will need after birth to push food through the digestive tract. The pituitary gland at the base of the brain has started producing hormones. And the bone marrow is making white blood cells, which will one day help your baby fight infection (including all those germs passed around the snot-nosed playgroup).
If you haven't already had the pleasure, it's likely that at this month's checkup you'll finally hear your baby's heartbeat — a sound that will make your heart race with joy!
Learn more about being 12 weeks pregnant.