I wouldn't have any procedure performed if I was one week pregnant, one month or even 9 months.  Miscarriages often happen up to the first trimester (first 3 months) and it is better safe than sorry to just take care of you and baby.

If you have symptoms that docs think require colonoscopy, I'd look into diet changes and daily bowel habits before I'd let anyone or anything invade my body where a baby has finally found a nice place to nestle for 9 months and hopefully without noisy neighbors poking around.

Congratulations on your pregnancy. Let your new life grow within you and protect it from invasive procedures unless it directly impacts that child's quality of life (gestation).

Good Luck to you.