Getting pregnant after c-section

When I went to my 6-week checkup, I mentioned to my ob/gyn that we are planning on getting pregnant again within the next 4 months or so. The doctor said that they advise any c-section patients not to get pregnant again for at least a year due to risk of premature birth and/or low birth weight. I had never heard this before - have you been told this? Have any of you experienced otherwise in your births?