What Are The Causes Of Miscarriage?

I had an ultrasound and an internal yesterday and measured 6 wk and 3 days pregnant. The fetal pole was seen and so was a heart beat but the gestational sac is said to be low down in my uterus. Doe sthis mean I am likely to miscarry? I only misccaried on the 15th January and caught on straight away. I am very worried.