What are the risks of an older woman having a baby?

My mom is 50 years old and she wants to have another baby. She already has me Bohdana (the eldest), my brother Gavril and my little sister Elana. I am 18, my brother is 15 and my sister is 14. My mom is worried she is going to hit the menopause very soon so she wants to have a baby. I am extremely worried about it however, because of her age and the fact that this baby will be the first one born in england away from my grandmother who is a midwife (we are from Russia originally, and my grandmother delivered me and my siblings). What are the risks that age creates for borth for the mother and the baby, if any? And how do I stop stressing about it?