It's hard to say. Typically, yes it can be more difficult in our 40's. However, some have no problem at all. Everyone's experience is a little different. The best thing to do is of course try for a few months, timing intercourse according to ovulation. If, after a few months you are not pregnant, you should consult an RE. In our 20's they typically won't look at you until you have been trying a year. But for us 40 somethings, it's best not to wait that long. I would say no more then 3 or 4 months. Other's might recommend you see one immediately, and I certainly wouldn't disagree with that. Good luck to you, I hope you are quickly successful!!
I'm 40, going on 41 and am trying for my 2nd. My 1st is 8 yrs old now. I've been trying for 7 mo now and my doc wants to see me in March if we have no luck. I think all docs are a little different. I went to my doc before we started trying so they could run some test and make sure everything was ok. I was glad cause my thyroid needed a little adjusting. It might be wise to have a pre conception visit if you can. Good luck and welcome!