I had a small Pygmy doe who accidentally got bred bred to a Saanen buck. I lost both momma and kid. When we raised beef cattle we had some registered Angus (moderate framed) cows and we decided to go with a huge Santa Gertrudis bull as our cross. BIG mistake! We lost a cow during calving and had another prolapse just after calving. Nine times out of ten, you want to breed a large breed female to the smaller breed of male. A friend breeds draft mules and he always breeds the male donkey (jack) to the big draft mare and never the other way around. I would get them the Lute injection if your vet says it is indicated. Your first time mommas, if they successfully carry to term and deliver without complication stand a great chance of prolapse or even infertility later on. I have seen this situation in many species of farm animal and 8 out of 10 times I have witnessed disaster.
Hate to be the bearer of bad news and who knows, things may go just fine but the odds are against you. Prayers for you though. God Bless.