I knocked off for law school and pregnancy . . . my OB made me quit in the fourth month - he said he wasn't worried about hurting the baby but about ME getting hurt due to changes in my CG and balance . . . he was right of course. I didn't really get back started again until my oldest was 7 or 8.
But when I climbed back on it was as though I had never been away. I will warn you, however, that while my muscles remembered what to do they were not physically ready for the effort, and I really overdid it the first time out. I was way too interested in finding out what I could still do - lots, but I could barely walk for a couple of days afterwards . . .
My Friesian-owning buddy laughed when I got up on Sam (the Friesian) - she said she'd have known I used to ride, because I turned my toes in.