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4 weeks
What's going on during the month : The amniotic sac, which will house your baby; the amniotic fluid, which will cushion her as she grows; and the yolk sac, which produces your baby's red blood cells and helps deliver nutrients to her until the placenta has developed and is ready to take over this duty. -
8 weeks
Webbed fingers and toes are poking out from your baby's hands and feet, his eyelids practically cover his eyes, breathing tubes extend from his throat to the branches of his developing lungs. -
12 weeks
The most dramatic development this week: reflexes. Your baby's fingers will soon begin to open and close, his toes will curl, his eye muscles will clench, and his mouth will make sucking movements. In fact, if you prod your abdomen, your baby will squirm in response, although you won't be able to feel it. -
16 weeks
. Right now, he's about the size of an avocado: 4 1/2 inches long (head to rump) and 3 1/2 ounces. His legs are much more developed, his head is more erect than it has been, and his eyes have moved closer to the front of his head. His ears are close to their final position, too. -
20 weeks
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24 weeks
Your baby's growing steadily, having gained about 4 ounces since last week. That puts him at just over a pound. Since he's almost a foot long (picture an ear of corn), he cuts a pretty lean figure at this point, but his body is filling out proportionally and he'll soon start to plump up. -
28 weeks
By this week, your baby weighs two and a quarter pounds (like a Chinese cabbage) and measures 14.8 inches from the top of her head to her heels. She can blink her eyes, which now sport lashes. With her eyesight developing, she may be able to see the light that filters in through your womb. -
32 weeks
By now, your baby weighs 3.75 pounds (pick up a large jicama) and is about 16.7 inches long, taking up a lot of space in your uterus. You're gaining about a pound a week and roughly half of that goes right to your baby. In fact, she'll gain a third to half of her birth weight during the next 7 weeks as she fattens up for survival outside the womb. She now has toenails, fingernails, and real hair. -
34 weeks
Your baby now weighs about 4 3/4 pounds and is almost 18 inches long. -
36 weeks
Your baby is still packing on the pounds — at the rate of about an ounce a day. She now weighs almost 6 pounds and is more than 18 1/2 -
40 weeks
It's hard to say for sure how big your baby will be, but the average newborn weighs about 7 1/2 pounds (a small pumpkin) and is about 20 inches long. His skull bones are not yet fused, which allows them to overlap a bit if it's a snug fit through the birth canal during labor.
