Exercising in early pregnancy & light spotting

So I’m only 4 1/2 weeks found out last week & my dr said it’s ok to continue exercising as long as my heart rate doesn’t go over 140. I worked out on Thursday & was spotting the next day, has this ever happened I’ve read it could be from working out.

Everything is ok so far my dr said the spotting was old blood & it stopped & my levels has doubled beautifully. But yes, I am high risk had three miscarriages in the last year but I was told I can continue exercising.