Ha ha I am starting to think so
I fell pregnant with my surprise DD a week or two after my best buddy had her first baby, admittedly we did have unprotected sex but I was at day 28 of my cycle!
Another of my friends fell pregnant around the time I had my DD. And I have heard of several other cases too
Maybe it just coincidence... or maybe when we hold a newborn and get that needy feeling we release hormones that make us extra fertile