TTC after special needs child?

​We have an 18 month old now, born at   33+5 after a car accident and subsequent premature water break, and ultimately a long labor only to end in a c section 25 hours later! As a result, she has Periventricular Leukomalacia (white matter brain damage and shrinkage) and cerebral palsy, along with a few other minor issues with eyes and swallowing. We were blessed because, as severe as her MRI shows, her physical appearance and cognitive abilities would never tell you she has special needs! She is physically developmentally delayed and at 18 months can only roll, no scooting crawling or walking YET. 

​Does anyone have experience with having a new baby AFTER a baby with special needs? How has it helped/harmed your special needs child? Most people typically stop after a special needs baby but we know our family isn't complete yet!