My sister had the 4th child when her 3rd was only 4 months. Both kids are 11 months apart but born different year. She didnt terminate pregnancy, however faces sharp tingling pain towards third trimester. Both kids are now 1 and 2 years old. She can do VBAC but choose C section due to the sharp tingling pain. You may seek advice from gynae pertainjng this issue during check up.