16 weeks pregnant today!

How your baby's growing:

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. He's even started growing toenails. And there's a lot happening inside as well. For example, his heart is now pumping about 25 quarts of blood each day, and this amount will continue to increase as your baby continues to develop.

Listen up: Tiny bones in your fetus's ears are in place this week, making it likely that the baby can hear your voice when you're speaking (or singing in the shower)at 16 weeks pregnant. In fact, studies have found that babies who are sung to while they're in the womb recognize the same tune when it's sung to them after they are born (so choose your baby Muzak with that in mind…).

And baby's busily adding bone in other ways. For one, the backbone (along with the back muscles) is stronger now — strong enough, in fact, to enable your baby to work on straightening his or her head and neck even more. Baby's crown-to-rump measurement is between four and five inches in length, and weight is hovering around three ounces.

This little one's a looker — with a face that has both eyebrows and eyelashes — but a skinny looker since there's no baby fat yet. And here's the skinny on baby skin: It's practically translucent now, so if you took a peek inside your uterus, you'd be able to see your baby's blood vessels under that thin skin.