Quoting Garcia Momma EBFB!: Aww that is so sweet!!! That kinda made me tear up, Did you ever take a picture of it for keepsakes?? ... [snip!] ... What about when the baby is born... do you have colustrum of is it milk... these are questions i have always wondered.
Often your supply will decrease as your milk slowly changes to colostrum. WHEN this happens varies woman to woman, but the "average" is 20 weeks. I had colostrum by 14 weeks and know women who don't have it until around 30 weeks.
Nursing won't cause labor unless your body is ready. If you end up in preterm labor from nursing, you probably would have had it anyway. Your body is used to nursing by the time you get pregnant, so it's similar to how you can continue any exercise program that doesn't risk blows to the abdomen while pregnant, but shouldn't start something rigorous and new.
The contractions nursing causes are similar to braxton hicks and many women don't even feel them while pregnant. I actually had less this past pregnancy while dry nursing a few times a week than I had with my first pregnancy.
Sex also causes similar contractions to what nursing causes and that is safe during pregnancy.
When the baby is born, your milk will be colostrum and it then comes in fully after a few days.