I was 14 weeks pregnant with my first child last fall when my right breast suddenly became very inflamed. At first, it was only the change in size that I noticed. But within a short time — maybe five days, max — it went from just being larger to hurting and turning very red.

I went to my regular OB/GYN, who thought it was mastitis — a milk duct infection. That would’ve been pretty unusual in someone who wasn’t actively breastfeeding...