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Week 36
Your baby is still packing on the pounds — at the rate of about an ounce a day. She now weighs almost 6 pounds (like a crenshaw melon) and is more than 18 1/2 inches long. She's shedding most of the downy covering of hair that covered her body as well as the vernix caseosa, the waxy substance that covered and protected her skin during her nine-month amniotic bath. Your baby swallows both of these substances, along with other secretions. -
Week 2
During the next 12 to 24 hours, that egg will be fertilized if one of the 250 million sperm (on average) your mate ejaculates manages to swim all the way from your vagina through your cervix, up into your uterus to the Fallopian tube, and penetrate the egg. Only about 400 sperm will survive the arduous ten-hour journey to the egg, and only one will succeed in burrowing through its outer membrane. (It takes about 20 minutes for the lucky winner to find its way in.) -
Week 4
This week marks the beginning of the embryonic period. From now until 10 weeks, all of your baby's organs will begin to develop and some will even begin to function. As a result, this is the time when she'll be most vulnerable to anything that might interfere with her development.
Right now your baby is an embryo the size of a poppy seed, consisting of two layers: the epiblast and the hypoblast, from which all of her organs and body parts will develop. -
Week 8
New this week: 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, and his "tail" is just about gone. In his brain, nerve cells are branching out to connect with one another, forming primitive neural pathways. You may be daydreaming about your baby as one sex or the other, but the external genitals still haven't developed enough to reveal whether you're havi -
Week 13
Fingerprints have formed on your baby's tiny fingertips, her veins and organs are clearly visible through her still-thin skin, and her body is starting to catch up with her head — which makes up just a third of her body size now. If you're having a girl, she now has more than 2 million eggs in her ovaries. Your baby is almost 3 inches long (the size of a medium shrimp) and weighs nearly an ounce. -
Week 16
Get ready for a growth spurt. In the next few weeks, your baby will double his weight and add inches to his length. 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. The patterning of his scalp has begun, though his locks aren't recognizable yet. -
Week 19
Your baby's sensory development is exploding! Her brain is designating specialized areas for smell, taste, hearing, vision, and touch. Some research suggests that she may be able to hear your voice now, so don't be shy about reading aloud, talking to her, or singing a happy tune if the mood strikes you.
Your baby weighs about 8 1/2 ounces and measures 6 inches, head to bottom — about the size of a large heirloom tomato. Her arms and legs are in the right proportions to each other. -
Week 26
The network of nerves in your baby's ears is better developed and more sensitive than before. He may now be able to hear both your voice and your partner's as you chat with each other. He's inhaling and exhaling small amounts of amniotic fluid, which is essential for the development of his lungs. These so-called breathing movements are also good practice for when he's born and takes that first gulp of air. And he's continuing to put on baby fat. He now weighs about a pound and two-thirds. -
Week 30
Your baby's about 15.7 inches long now, and she weighs almost 3 pounds (like a head of cabbage). A pint and a half of amniotic fluid surrounds her, but that volume will decrease as she gets bigger and takes up more room in your uterus. Her eyesight continues to develop, though it's not very keen; even after she's born, she'll keep her eyes closed for a good part of the day. When she does open them, she'll respond to changes in light but will have 20/400 vision. -
Week 40
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. This so-called "molding" is the reason your baby's noggin may look a little conehead-ish after birth. Rest assured — it's normal and temporary.
