Onion or uterine parasite?

Sept. 1: I’m now at 17 weeks of pregnancy, and there have been quite a few times in the last week that I felt a little bubble-like sensation.  I’m pretty sure it’s the little one starting to say hello.  This has been a really easy pregnancy thus-far.  Andrew seems to enjoy saying good morning to the “teeny tiny” in Mama’s belly, and he’s doing a lot of baby roll-playing these days.
I have my next prenatal appointment in a couple weeks.  Not particulary showing yet, but I seem to remember that it was just after week 20 that I really “popped” with Andrew.  This little person is keeping me hungry and happy.  I am enjoying this part of pregnancy where things are pretty low-key.  One of my neighbors is due any moment.  The anticipation!

Here’s the Week 17 Update from Babycenter.com:

Your baby weighs about 5 ounces now,
and he’s around 5 inches long — about the size of a large onion. The umbilical cord, his lifeline to the placenta, is growing stronger and thicker. Your baby can move his joints, and his skeleton — until now, rubbery cartilage — is starting to harden into bone.
Some of it will remain cartilage for years after he’s born. A newborn’s skeleton has 300 parts (a combination of bone and cartilage). As your child grows, some of these parts harden and fuse together. By the time your baby reaches adulthood, he’ll have just 206 bones.