Evelyn,
Lots of women in their 40's have babies. I haven't been pregnant since I was 38 and have great hormone levels. So fertility does decline rapidly due to aging eggs. But some IVF clinics will still take women until they are 43. So if you are serious about having that third child, fertility specialists will likely still work with you granted your hormone levels are still good. Seven or eight years age difference isn't that big of a deal, at least to me. ;-)