Blood Pressure.. High vs Low?

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I know high blood pressure is common and very dangerous during pregnancy. But what about low blood pressure? In the second trimester I’ve had episodes where I felt like I wanted to pass out. This only occurred when I was standing up. Now being 33 weeks and in the third trimester, this feeling has been happening more frequently and now even so when I’m sitting or laying down. I get dizzy/lightheaded and sometimes it freaks me out because I feel like I’m gonna pass out. Sometimes it’s hard to breathe and I get super nauseous.

My father in law took my blood pressure today and was 110/50. I know the systolic is okay but diastolic seems rather low. He even said it was low. Is there any reason for concern about this? What are the risks, if any, to my baby?