When you’re expecting, every week brings new developments and new experiences. Your baby is changing every single day, and your body is experiencing changes and developments of its own. Find out what’s going on with your baby and pregnancy week by week.
[mighty_toggle title=”Trimester One” state=”closed”]
After fertilization and implantation, a baby is at first just an embryo. Growing quickly, your baby is soon about the size of a kidney bean. Within the first trimester, the heart is beating rapidly and the intestines are starting to form. Earlobes, eyelids, mouth, and nose are also starting to take shape.
Weeks 1-3
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 pregnancy
Week 4
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.
Week 5
Your baby now resembles a teeny tadpole (complete with a tiny tail) and is about the size of an orange seed. The circulatory (or blood) system, along with the heart, is the first part of that tiny body to be functional; and as your baby’s heart starts to form, you may even be able to see it beating on an early ultrasound. Another part of your little tadpole that is under construction: the neural tube, which will eventually become your baby’s brain and spinal cord.
Week 6
Your baby’s jaw, cheeks, chin, eyes, ears, and nose are beginning to form what will eventually become one adorable face. In addition, her kidneys, liver, and lungs are developing, and her heart is now beating 80 times a minute (and getting faster every day). All this and she’s still no bigger than the length of a nail head
Week 7
Your baby is now about the size of a blueberry (and about 10,000 times bigger than he was at conception). Most of that growth is concentrated in the head as new brain cells are generated at the rate of 100 per minute. Your baby’s mouth and tongue are forming as arm and leg buds sprout, and those little kidneys are getting ready to do their job
Week 8
Your little one is looking a lot more baby-like these days, as her lips, nose, eyelids, legs, and back continue to take shape. Her heart is beating at the incredible rate of 150 times per minute — about twice as fast as yours! And even though you can’t yet feel it, she’s now making spontaneous movements as she twitches her tiny trunk and limb buds.
Week 9
Your baby, now the size of a green olive, has grown about an inch since last week. Tiny muscles are beginning to form, so while he might not be ready to pump iron, he’s gearing up to move his arms and legs. It’s still too soon to feel anything in your belly, but you might be able to hear something at your next checkup. Try listening for your baby’s heartbeat via a Doppler device — that welcome sound should be audible anytime now
Week 10
Your baby (now the size of a prune) has small indentations on his legs (soon to be knees and ankles!), and his tiny arms even have elbows that bend (how is that for magical?). Inside that little mouth, tiny buds of baby teeth are forming under the gums. His stomach and kidneys are kicking into gear, producing digestive juices and urine
Week 11
Your baby (now about two inches long) has been pretty busy this week, growing hair follicles, fingernails, and ovaries (if she’s a girl). She has distinct human characteristics by now, with hands and feet in front of her body, with ears nearly in their final shape, open nasal passages on the tip of her tiny nose, a tongue and palate in the mouth,
Week 12
By now, your baby weighs a full half-ounce and is about the size of a large plum. Most of his systems are in place, though there’s still plenty of maturing to do. For one thing, his fetal digestive system is beginning to practice contraction movements necessary for eating, and his bone marrow is busy making white blood cells — weapons against germs once he’s out of your safe haven.
Week 13
Tiny bones are beginning to form in her arms and legs, the intestines are beginning to move from the umbilical cord to the abdomen, and the vocal cords are well under construction (the first step toward saying, “I love you, Mommy!”). And because she can move her arms and legs in a jerky fashion, she may be able to get her thumb into her mouth (a habit that may come in handy for self-soothing when she’s a newborn.
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[mighty_toggle title=”Trimester Two” state=”closed”]
“At the beginning of the second trimester, babies are about 3 1/2 inches long and weigh about 1 1/2 ounces. Tiny, unique fingerprints are now in place, and the heart pumps 25 quarts of blood a day. As the weeks go by, your baby’s skeleton starts to harden from rubbery cartilage to bone, and he or she develops the ability to hear. You’re likely to feel kicks and flutters soon if you haven’t already.”
Week 14
Now the size of your clenched fist, your baby is more fluid-like in his movements, so he’s no longer doing the jerk every time he repositions his arms and legs. His intestines are producing meconium (which is the waste that will make up his first bowel movement after birth). He is also sporting a downy coating of hair (lanugo) that keeps him nice and warm
Week 15
She’s about the size of an orange this week, her ears have migrated to the sides of her head, and her eyes are moving to the front of her face. Plus, she/he now wiggle their fingers and toes and make breathing movements in preparation for life outside the womb.
Week 16
Your baby now weighs in at a whopping three to five ounces, and he’s four to five inches in length. The bones that are now in place in his ears means he can probably hear your voice as you talk. While he’s getting used to your voice, the tiny muscles in his body, especially the ones in his back, are gaining strength, so he can straighten out a little more. His developing facial muscles, show that your baby is capable of making a few expressive frowns and squints, even at this early stage.
Week 17
She’s about the size of your palm, weighs about five ounces, and is developing some body fat .Her heart is now regulated by her brain (no more random beats) to beat 140 to 150 times per minute — about twice as fast as yours! Other survival skills include sucking and swallowing
Week 18
At five and a half inches long and five ounces in weight, he now may be large enough for you to feel him twisting, rolling, kicking, and punching his way around the womb. Plus, he’s developing yawning and hiccupping skills (you may feel those soon, too!) and his own unique set of toe and fingerprints.
Week 19
She’s about a half pound in weight and six inches long) and a substance called vernix caseosa. This greasy white stuff covers your baby’s skin, protecting it from the surrounding amniotic fluid.
Week 20
Curious about whether that melon-sized belly contains a boy or a girl? Now’s your chance to take a peek! Your second trimester ultrasound scheduled for anytime between 18 and 22 weeks, gives your practitioner a chance to see how things are going in there. If you’re having a girl, her uterus is now fully formed and her ovaries are holding about seven million primitive eggs. If you’re having a boy, his testicles have begun their descent from the abdomen to their ultimate destination — the scrotum. And while your baby is definitely getting bigger (weighing in at about ten ounces and measuring six and a half inches), there’s still plenty of growing room in there, which allows him to twist and turn (and allows you to feel his acrobatics!).
Week 21
He size of a large banana and if you eat one this week, there’s a good chance your baby will get a taste, too. That’s because he swallows a bit of amniotic fluid each day (for nutrition, hydration, and to practice digesting), so he eats whatever’s on your menu — and gets to put those developing taste buds to good use. So go ahead and nosh on those nachos (or crunch those crudités): Your baby may develop a taste for them when he’s older
Week 22
This week, your baby weighs in at a whopping pound and measures nearly eight inches, about the size of a small doll. But your little doll (who now has eyebrows, eyelashes, and maybe even some hair on that little head) is a living one who can now perceive light and dark. She can also hear your voice, your heartbeat, your gurgling stomach, and the whoosh-whoosh of blood circulating through your body. And as her brain and nerve endings develop, she may reach for her face (or whatever she can reach) just to experiment with her newfound sense of touch.
Week 23
Beginning this week, he’ll start to pack on the pounds (which means you will too!) and by month’s end he’ll be double the weight he is now (though you won’t be — whew!). Right now, your baby’s organs and bones are visible through his skin, which has a red hue due to developing veins and arteries beneath
Week 24
Your baby is about eight and a half inches long and weighs one and a half pounds, gaining steadily at a rate of six ounces per week. Much of that weight comes from accumulating baby fat, as well as from growing organs, bones, and muscle. Those little ears of hers are getting sharper and can hear very loud sounds, from a yapping dog to a jackhammer. Also by now, that fabulous face is almost fully formed, complete with eyelashes, eyebrows, and hair
Week 25
Your baby is growing by leaps and bounds, reaching nine inches in length and passing the pound and a half mark. Under his skin, capillaries are forming and filling with blood and by week’s end, air sacs (also lined with capillaries) will develop in his lungs, getting them ready for that first breath. Mind you, those lungs aren’t ready for prime time just yet — but they are developing surfactant, a substance that will help them expand after birth. And speaking of breathing, your baby’s tiny nostrils, which have been plugged up until now, are starting to open, and his vocal chords are getting ready to roar.
Week 26
She now weighs a full two pounds and measures nine-plus inches. And this week, her eyes, which until now were developing under fused eyelids, start to open. Of course, there’s not much to see in there, but if your baby spots a bright light (or hears a loud noise) near your belly, you may notice an increase in fetal activity. In addition her brain is becoming more developed and sophisticated.
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[mighty_toggle title=”Trimester Three” state=”closed”]
“Babies weigh about 2 1/4 pounds by the start of the third trimester. They can blink their eyes, which now sport lashes. And their wrinkled skin is starting to smooth out as they put on baby fat. They’re also developing fingernails, toenails, and real hair (or at least some peach fuzz), and adding billions of neurons to their brain. Your blossoming baby will spend his or her final weeks in utero putting on weight. At full term, the average baby is more than 19 inches long and weighs nearly 7 pounds.”
Week 27
Your baby is about fifteen inches — more than a foot long — and triple (or even quadruple) what it was in week 12. His weight is creeping up the charts as well, coming in at just over two pounds. More big news: Your baby may recognize your voice by now, so feel free to serenade your belly (start learning those lullabies!)
Week 28
Your baby is settling into the proper position for birth, with his head facing downward). She/he is progressing to about 2.5 pounds and almost 16 inches long. He’s busy adding new skills such as blinking to an already impressive repertoire of tricks like coughing, sucking, hiccupping, and taking practice breaths.
Week 29
She weighs nearly three pounds now and measures about 17 inches. Though shes getting close to her birth length she still has to chub up a bit. Over the nex 11 weeks she more than double or triple her weight. And as she grows and the room in your womb gets tighter, you’ll be less likely to feel those kicks and jabs.
Week 30
His brain is growing daily and is actually starting to look like the real thing with those characteristic grooves and wrinkles. And now that your little genius can regulate his own body temperature and turn up the heat, he’ll start shedding lanugo, the downy body hair that’s been keeping him warm up until now.
Week 31
He’s now processing information, tracking light, and perceiving signals from all five senses. 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).
Week 32
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. Something else to note: As more and more fat accumulates under your baby’s skin, she’s becoming less transparent and more opaque.
Week 33
With that much baby inside your uterus, your amniotic-fluid level has maxed out, which explains why some of her pokes and kicks feel pretty sharp these days. (There’s less fluid to cushion the blows.) Antibodies are being passed from you to your little one as she continues to develop her own fetal immune system, which will come in handy once she’s outside the womb and fending off all sorts of germs.
Week 34
Those tiny fingernails have probably reached the tips of his fingers by now — and getting ready for that first postpartum manicure.
Week 35
Growing at an amazing pace is your baby’s brain power. But 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.
Week 36
Most of her systems (from circulatory to musculoskeletal) are ready, though her digestion system will kick into gear as she takes her first suckle at the breast or bottle
Week 37
Your baby is simulating breathing by inhaling and exhaling amniotic fluid, sucking on his or her thumb, blinking, and pivoting from side to side
Week 38
Fetal development is nearly complete as your baby tends to a few last-minute details like shedding the skin-protecting vernix and lanugo. He’s also producing more surfactant, a substance that prevents the air sacs in his lungs from sticking to one another once he starts to breathe
Week 39
Her pink skin has now turned whitish. Her head may have dropped into your pelvis by now, which makes your breathing easier but walking harder.
Week 40
Still providing the antibodies he’ll need to fight off infections for the first six months of his life. And if you plan on breastfeeding, your milk will be giving him more antibodies that’ll boost his immune system.
Week 41
Fewer than five percent of babies are born on their actual due dates — and around 50 percent decide to overstay their welcome
Week 42
To be sure all is well, your practitioner will likely monitor your overdue baby through non-stress tests (you’re hooked up to a fetal monitor to measure your baby’s heart rate and movement) and amniotic-fluid checks. When this latecomer finally makes her debut, chances are her skin will be dry, cracked, peeling, or wrinkled — all completely temporary. That’s because the protective vernix was shed weeks ago in anticipation of a delivery date that came and went.
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Interested in learning more about the wonders of pregnancy? Here’s 7 Awesome Things Your Body Does During Pregnancy