I know I am super late on this, but I have been way too tired and sick to post.
This week, Ziggy is the size of an apple seed:
Your embryo, which doesn't look like much more than a tadpole right now, is actually starting to form major organs (heart, kidney, lover stomach) and systems (nervous, circulatory, digestive). Baby's presence in your uterus triggers production of HCG (the hormone detected by pregnancy tests), which triggers the production of hormones like estrogen and progesterone, which triggers all those great symptoms you've probably been noticing!
Now for the weekly questions:
