Why did my stop growing at 13 weeks?

Mine grew a cup size and then have leveled off since 13 weeks- am now 25 weeks and they are still the same. I am sure they will get bigger though the further I go. Usually they measure you for a nursing bra one month prior to delivery and order up one size for your milk. So definately by the time you are one month prior they will be a little bigger and for sure when the milk comes in. Don't worry- you have lots of time for to grow!