My daughters are 21 months apart. The pregnancy wasn't really any different second time around although I did put on an 5 extra kg and bub was a pound bigger. I found the 21 month gap really tough and actually suffered PND when bub #2 was about 8 months old. In hindsight, a 2.5 year age gap would have been easier, I think. I am now expecting bub #3. This time there will be a 3 year and 3 month gap between bub 2 and 3.