Mine were from IVF. I was 41 when I got pregnant - 42 when I had them.
We were very lucky to have conveived them on the first attempt - especially given that the clinic gave us a 11% chance of success when we first started the treatment (the Lister). But my personal probability of success was probably much higher - 1) we had no identified fertility issues - we married late - tried for 6 months and thought that at my age we had better just get on with it 2) I had a very low FSH 3) we ended by having a blastocyst transfer at 6 days which has a much higher probability of success than a regular 2 or 3 day transfer.
So you need to talk to your clinic about your personal situation cos its not the same as every other 40 year old out there even though they clump as all together.
I remember clearly being in the embryo implantation room and discussing with the Dr and DH about how many to put back in. Given low probability of success we went for two - did not in my wildest dreams think it would work - let alone twins.
I was horrified when I found out it was twins(my sister also had IVF twins (it runs in the family ) and I remembered how huge she was in month 7 and was terrified.
But now nearly 6 months on, I know that we are truely blessed. Two babies at my age - a family on one go .
We are just having sooo much fun. Its great .
BUT .... we did have some serious chats about what would happen if it didnt work . How many attempts would we go through? - its emotionally and finacially draining. What sort of life would we have without kids? We know some lovely couples in their fifties with no children who have great lifestyles - go on holiday loads, have active social lives, have loads of interests and love each other and their companionship very much. And we talked about how much we loved each other and how we would be content with a childless life just with each other if it didnt work out.
Life with and without children is just what you make it. You have got to make the most of it whatever your situation.
So good luck in whatever fate has in store for you.
But dont be scared of having twins - its really quite wonderful.