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Week 1
Your egg and his sperm haven't met yet. -
Week 2
This may sound strange, but you're still not pregnant! Fertilization of your egg by the sperm will only take place near the end of this week -
Week 3
Even though you may not feel that you're pregnant yet, you have a baby growing and developing inside of you!
The fertilized egg goes through a process of cell division. About 30 hours after fertilization, it divides into two cells, then four cells, then eight, and continues to divide as it moves from the fallopian tube to the uterus. -
Week 4
Four weeks into your pregnancy, your baby (called an embryo) consists of two layers of cells — the epiblast and the hypoblast — that will eventually develop into all of your baby's organs and body parts. -
Week 5
Until now, the embryo has been a mass of cells, but by this point in your pregnancy a distinct shape begins to form. The neural tube, which will eventually form into the spinal cord and brain, runs from the top to the bottom of the embryo. -
Week 6
By week 6, your baby’s brain and nervous system are developing at a rapid pace. Optic vesicles, which later form the eyes, begin to develop this week on the sides of the head, as do the passageways that will make up the inner ear. -
Week 7
Your baby is constantly adapting to life inside the uterus. By this week, the umbilical cord has formed. It will be your baby’s connection to you throughout your pregnancy, providing oxygen and nourishment for your baby and disposing of your baby's wastes. In addition, your baby's digestive tract and lungs continue to form. -
Week 11
From this week until week 20, your baby will be growing rapidly — increasing in size from about 2 inches (5 cm) to about 8 inches (20 cm) from crown to rump. To accommodate all this growth, the blood vessels in the placenta are increasing in both size and number to provide the baby with more nutrients. -
Week 8
Marveling over a baby's tiny fingers and toes is one of the joys of the first day of life. Those fingers and toes are just beginning to form this week, and the arms can even flex at the elbows and wrists. The eyes are becoming more obvious because they’ve begun to develop pigment (color) in the retina (back of the eye). -
Week 12
Your baby's brain continues to develop, and tiny fingernails and toenails start to form. Vocal cords are formed this week, which is the last of your first trimester. -
Week 9
The tail at the bottom of your baby's spinal cord has shrunk and almost disappeared by this week. In contrast, your baby's head has been growing — it's quite large compared with the rest of the body and it curves onto the chest. By this week, your baby measures about 0.6 to 0.7 inches (16 to 18 millimeters) from crown to rump and weighs around 0.1 ounces (3 grams). The tip of the nose has developed and can be seen in profile, and flaps of skin over the eyes have begun to shape into eyelids, whic -
Week 13
As you begin the second trimester of pregnancy, your placenta has developed and is providing your baby with oxygen, nutrients, and waste disposal. The placenta also produces the hormones progesterone and estrogen, which help to maintain the pregnancy. -
Week 10
By week 10, all of your baby's vital organs have been formed and are starting to work together. -
Week 14
By this week, some fine hairs have developed on your baby's face. This soft colorless hair is called lanugo, and it will eventually cover most of your baby's body until it is shed just before delivery. -
Week 15
Parents are often amazed by the softness of their newborn's skin. Your baby’s skin has been continuously developing, and it is so thin and translucent that you can see the blood vessels through it. Hair growth continues on the eyebrows and the head. Your baby's ears are almost in position now, although they are still set a bit low on the head. -
Week 16
Your baby now weighs about 3.9 ounces (110 grams) and measures about 4.7 inches (12 cm) in length from crown to rump. Your baby can hold his or her head erect, and the development of facial muscles allows for a variety of expressions, such as squinting and frowning. -
Week 17
At about 5.1 inches (13 cm) from crown to rump and weighing 4.9 ounces (140 grams), your baby is still very tiny. The placenta, which nourishes the fetus with nutrients and oxygen and removes wastes, is growing to accommodate your baby. It now contains thousands of blood vessels that bring nutrients and oxygen from your body to your baby's developing body. -
Week 18
Ears move to their final position and they stand out from the head. And start brushing up on your lullabies — in the coming weeks, your baby will probably be able to hear! The bones of the middle ear and the nerve endings from the brain are developing so that your baby will hear sounds such as your heartbeat and blood moving through the umbilical cord. He or she may even be startled by loud noises! -
Week 19
Your baby is now covered with a white, waxy substance called vernix caseosa, which helps prevent delicate skin from becoming chapped or scratched. Premature babies may be covered in this cheesy coating at delivery. -
Week 20
You're halfway there! Twenty weeks into your pregnancy, your baby has grown significantly from that first dividing cell and now weighs about 11 ounces (312 grams) and measures about 6.3 inches (16 cm) from crown to rump. The baby is taking up increasing room in your uterus, and continued growth will put pressure on your lungs, stomach, bladder, and kidneys. -
Week 21
The amniotic fluid that has cushioned and supported your baby in the uterus now serves another purpose. The intestines have developed enough that small amounts of sugars can be absorbed from the fluid that is swallowed and passed through the digestive system to the large bowel. Almost all of your baby's nourishment, however, still comes from you through the placenta. -
Week 22
Even though fat is beginning to accumulate on your baby's body, the skin still hangs loosely, giving your baby a wrinkled appearance. Your baby's daily workout routine includes moving the muscles in the fingers, toes, arms, and legs regularly. As a result, you may feel more forceful movements. -
Week23
Even though fat is beginning to accumulate on your baby's body, the skin still hangs loosely, giving your baby a wrinkled appearance. Your baby's daily workout routine includes moving the muscles in the fingers, toes, arms, and legs regularly. As a result, you may feel more forceful movements. -
Week 24
Your baby is still receiving oxygen through the placenta. But once birth occurs, his or her lungs will start taking in oxygen on their own. In preparation for that, your baby's lungs are developing the ability to produce surfactant. Surfactant is a substance that keeps the air sacs in our lungs from collapsing and sticking together when we exhale, allowing us to breathe properly. -
Week 25
You may notice that your baby has resting and alert periods. You'll notice fetal activity more readily when you are more sedentary. Your baby's hearing has continued to develop, too — he or she may now be able to hear your voice! -
Week 26
Although your baby's eyes have been sealed shut for the last few months, they will soon open and begin to blink. Depending on ethnicity, some babies will be born with blue or gray-blue eyes (which may change color in the first year of life) and some will be born with brown or dark eyes. Eyelashes are growing in, as is more hair on the head. -
Week 27
Your baby now weighs about 2 pounds, 2 ounces (1,000 grams) and measures about 10 inches (25 cm) from crown to rump. At your next prenatal appointment, your health care provider may tell you whether your baby is headfirst or feet- or bottom-first (called breech position) in the womb. Babies who are in the breech position may need to be delivered by cesarean section. Your baby still has 2 months to change position, though, so don't worry if your baby is in the breech position right now. Most babi -
Week 28
Your baby now weighs about 2 pounds, 2 ounces (1,000 grams) and measures about 10 inches (25 cm) from crown to rump. At your next prenatal appointment, your health care provider may tell you whether your baby is headfirst or feet- or bottom-first (called breech position) in the womb. Babies who are in the breech position may need to be delivered by cesarean section. -
Week 29
Your baby continues to be active, and those first few flutters of movement have given way to hard jabs and punches that may take your breath away. If you notice a decrease in movement, do a fetal kick count: your baby should move at least 10 times in two hours. If your baby moves less, talk to your health care provider. -
Week 30
Now weighing about 3 pounds (1,400 grams) and measuring about 10.8 inches (27 cm) from crown to rump, your baby continues to gain weight and layers of fat. This fat makes the baby look less wrinkly and will help provide warmth after birth. -
Week 31
By now your baby is urinating approximately several cups of urine a day into the amniotic fluid. He or she is also swallowing amniotic fluid, which is completely replaced several times a day. Excess fluid in the amniotic sac (known as polyhydramnios) may mean that the baby isn't swallowing normally or that there is a gastrointestinal obstruction. Inadequate fluid in the amniotic sac (oligohydramnios) may mean that the baby isn't urinating properly and could indicate a problem with the kidneys or -
Week 32
The final touches are being placed on your baby masterpiece. Eyelashes, eyebrows, and the hair on your baby's head are evident. The lanugo hair that has covered your baby since the beginning of the second trimester is falling off, although some may remain on the shoulders and back at birth. -
Week 33
In these last few weeks before delivery, the billions of developed neurons in your baby's brain are helping him or her to learn about the in-utero environment — your baby can listen, feel, and even see somewhat. Your baby’s eyes can detect light and the pupils can constrict and dilate in response to light. Like a newborn, your baby sleeps much of the time and even experiences the rapid eye movement (REM) stage, the sleep stage during which our most vivid dreams occur! -
Week 34
Maternal calcium intake is extremely important during pregnancy because the baby will draw calcium from the mother to make and harden bone. If a pregnant woman doesn't get enough calcium during pregnancy, it can affect her own bones because the developing fetus will take minerals from the mother's skeletal structure as needed. -
Week 35
Your baby already weighs about 5 pounds, 5 ounces (2,400 grams), but this week begins your baby's most rapid period of weight gain — about 8 to 12 ounces (226 to 340 grams) each week! Fat is being deposited all over your baby's body, especially around the shoulders. -
Week 36
The wrinkly, tiny fetus you may have seen on earlier ultrasounds has given way to an almost plump baby. There is fat on your baby’s cheeks, and powerful sucking muscles also contribute to your baby's full face. Your baby now weighs a little under 6 pounds (2,721 grams). -
Week 37
This week, your baby is considered full-term! But your baby hasn't stopped growing yet. He or she continues to develop fat at the rate of half an ounce (14 grams) a day. In general, boys weigh more than girls at birth. -
Week 38
Your baby weighs about 6 pounds, 6 ounces (2,900 grams) by now and measures about 13.4 inches (34 cm) in length from crown to rump. Fat is still accumulating, although growth is slower now. You may notice that your weight gain has decreased or ceased. -
Week 39
Umbilical cords, which carry nutrients from the placenta to the baby, vary in size but average about 22 inches (55 cm) long and half an inch (1-2 cm) thick. Sometimes the umbilical cord can become wrapped around a baby’s neck. Generally, this doesn’t cause problems, although a cesarean delivery could be required if it causes pressure on the umbilical cord during labor or delivery. A true knot in the umbilical cord is much less common, occurring in only about 1% of pregnancies. -
Week 40
After many weeks of anticipation and preparation, your baby is here! Or maybe not — only 5% of women deliver on their estimated due dates, and many first-time mothers find themselves waiting up to 2 weeks after their due date for their baby to arrive.