I have a friend who has girls almost exactly 1 yr apart...
She was just a bit shocked!
She hadn't had a period at all.
She got pregnant 3 months post while breastfeeding a newborn around the clock with no supplements and no breaks.
She breast fed through the pregnancy, gave birth to a healthy baby, and continued to co-nurse.
It was hard on her... real WORK.
But she did it.