Mary my thoughts and prayers are with you. I lost my mom to a very very serious stomach cancer in September. My Dad had cancer at the same time and is doing great. Everyone is correct that ovarian cancer is very curable. Sorry this is so long but want to share my knowledge.
First go to acor.org - cancer resource site. I used it constantly. You can sign up for the ovarian cancer listserv and speak with people who have the illness, family members coping. I got such great info from people from around the world. As family members we are expected to make medical decisions and from this site I was able to run all the questions by those who had been there.
Second, it is ok to say to a doctor "Give us a day to decide" on certain treatments. Then you get on the listserv, get second opinions, check in with family. Doctors are mostly focused on chemo and radiation. Sometimes there are alternatives, or combo treatments.
Also, get all your mom's paper work in order now - health care proxy especially. I would also make sure that one of you get yourself on her checking or savings accounts and pin #s in case you need access to her money (my mom would not let us pay for anything so we'd be going to the cash machine constantly; she tipped the health care aides all the time!). Get copies made of all her health insurance id numbers - good to know when you call them and they say, "Oh sorry without the id number we can't tell you anything". For the times she is not lucid you or a sibling or someone may be asked, or will ask, to make decisions about treatment. I did this when my mom had a bad reaction to treatment that made her a bit whacky.
Final advice: you are pregnant. Put you and your baby first or you will be no good to your mother. You are a mom, wouldn't you tell your children the same? Feel no guilt.
I have been there. Please please please feel free to ask me any questions in the coming weeks. There is hope, there are wonderful moments to come out of this misery. To quote my mom, "Expect miracles!!"
All the best,
Julie