Feeling feverish, shivery, and sore on one side of your back during pregnancy is not something to put down to normal aches. These are classic kidney infection symptoms in pregnancy and they need medical attention the same day. A kidney infection, known medically as pyelonephritis, is one of the most common reasons pregnant women are admitted to hospital outside of obstetric emergencies. It affects around 1–2% of pregnant women and carries real risks for both mother and baby.