It doesn't help that, for many years, the advice given to pregnant women erred on the side of the conservative. Historically, women were instructed to get as much rest as possible, and to refrain from doing anything too athletic. Doctors were concerned that exercise might increase the risk of preterm delivery, or cause stress to the growing fetus.
This is a companion discussion topic for the original article at https://patient.info/news-and-features/how-to-keep-your-exercise-routine-going-while-pregnant