This week your baby may be anywhere between 17 to 19 inches in length and weigh more than four and a half pounds. Your baby could grow a full inch more this week alone — especially if he or she has been on the shorter side. Weight gain can range from a third more growth to a full doubling before the big debut.
The level of amniotic fluid in your uterus has reached its maximum, making it likely that you have more baby than fluid now. That's one reason why you're probably feeling lots of nudges and pushes — there's less liquid to cushion the blows. (Of course that means you're even closer to your baby now!)
If your uterine walls had eyes, here's what you'd see: your fetus acting more and more like a baby, with his or her eyes closing during sleep and opening while awake. And because those uterine walls are becoming thinner, more light penetrates the womb, helping your baby differentiate between day and night (now if only baby can remember that difference on the outside!).
And good news! Your baby has reached an important milestone about now: The development of his or her own immune system that (along with antibodies from you) will be able to provide protection from mild infections.