There is a
lot of disagreement over whether breastfeeding can contribute to miscarriage. I haven't come across anything to convince me that the two are connected, & like I said I have nursed through two pregnancies.
Here's an article from La Leche League on the issue.
Here is a PDF file on the same topic.
The theory seems to be that since nursing is known to stimulate the production of oxytocin, it can cause uterine contractions. This is something both links deal with specifically. The short version is that there is just no scientific evidence linking the two. However, it is such a personal decision, and if you want to avoid anything that has the slightest chance of causing a miscarriage, that makes perfect sense to me.
Your doctor probably will tell you to wean if you bring the subject up. I never did.
My nurse when I had Esther was just dumbfounded that my midwife "let" me continue to nurse while I was pregnant.
As if!
But it's all about what works for you.
And, before I forget:
Congratulations!