I have O- blood and DH is +, so it's been recommended that I get the Rhogam shot around 28 weeks pregnant. My midwives say the blood type difference is unlikely to affect this pregnancy, which is why it's "recommended" and not something they make you do (I know they can't actually make you, just making a point). Anyway, some things I've read definitely recommend it more strongly than others. Anyone have experience with this? Are there any negative effects to doing it, other than an extra shot (which isn't a big deal)?