Low heartbeat

Well I went for my ultrasound on the 28th of Oct. The tec had no trouble finding the gestational sac, and we saw the yolk sac. The baby measured small, for the week that I was in, but we saw a heartbeat! It was good that we saw one, but it was measuring at 91 which is pretty low for almost 8 weeks. The doctor ordered another ultrasound to be done next week, and from what I've read, as long as the heart rate has gone up, its fine. However, the chance the baby will not make it, is also a possibility. It could be that I ovulated late, and the heartbeat just started and anywhere from 90-130 is normal for a heartbeat just beginning. I will update you all when I have my next ultrasound on Nov 5th. Please be praying for this baby, I hope it turns out to be a miracle just like our first little one!