I Am 44 Years Old, I Have Had 16 Pregnancies

I am 44 years old, I have had 16 pregnancies and 11 live births. I have just recently found out that I am 6 week pregnant with twins. ( after they told us 2 years ago I would never get pregnant again) what is the risk of miscarriages. online they say the risks re at least 60% but I was wondering how much does IVF and those types of miscarriages impact that number? what are the risks for twins at my age? all of my previous births were natural and normal either than one placenta abruption doing labor that still ended in a live birth