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The BP value you mentioned is low and lower for as pregnant woman.The growth of the fetus depends on the blood perfusion to the uterus
and perfusion is maintained well if BP is normal. I would advice to recheck your BP for another three more times at different timings of different days consecutively . Confirm the low BP
To prevent the low BP you may have to keep your hydration good , hence drink more water and juices , also add salt to the food or the juices both of the efforts will surely help to gain the BP , if no improvement then you may have to visit a gynecologist.
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