Strep throat is not particularly dangerous during pregnancy. Of course, it makes sense to seek diagnosis as quickly as possible, and to take the prescribed course of antibiotics. All penicillins and cephalosporins are considered safe in pregnancy.
The only issue that I get a little concerned about is fever. We know that fever isn’t good for the baby, particularly during the first trimester when fetal organs are forming. So any mom-to-be who gets a fever in pregnancy is advised to take acetaminophen and bring down her temperature quickly. If fever persists, a call to the doctor or midwife is in order.