High Risk?

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Hoping you ladies can give me some insight! I have 3 children and I'm currently pregnant with number 4! Over the moon with joy!!! Buuut can't help but think about my previous pregnancies. Each were premature. First at 35 weeks, second at 34 weeks and third at 27 weeks. I was never labeled high risk with any of them and no explanation whatsoever on why my children are born premature. My first appointment with Ob is May 7th. So my questions to you ladies are: Are my chances pretty high of being high risk? And if I am what should I expect with being a high risk pregnancy? All comments are greatly appreciated! Thanks in advance!